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CONSTRUCTIBILITY REVIEW AND ECONOMIC ANALYSIS
FOR THE INSTALLATION OF LARGE-DIAMETER
HDPE DRAINAGE PIPE
by
MOHAMMED DIDARUL ALAM, B.E.
A THESIS
IN
CIVIL ENGINEERING
Submitted to the Graduate Faculty of Texas Tech University in
Partial Fulfillment of the Requirements for
the Degree of
MASTER OF SCIENCE
IN
CIVIL ENGINEERING
Appr£)ved
ClVaic^er^bn of the Committee
Accepted
uean of ±he Graduate School
/august, 2000
ACKNOWLEDGEMENTS
The research project with regard to this thesis was sponsored by Texas
Department of Transportation. I would like to show my appreciation to all TxDOT
officials who made the decision to provide support for conducting this research.
I express my deepest gratitude to my advisor. Dr. Priyantha Jayawickrama,
Associate Professor of Civil Engineering, for his guidance. This work would not be
possible without the tremendous effort put by him.
I am thankful to Dr. Sanjaya Senadheera for kindly serving as a member of my
thesis committee. I am truly indebted to Dr. Doug Gransberg, Professor of Engineering
Technology for providing his precious suggestions while conducting the research for this
thesis. Special thanks is extended to Dr. Scott Phelan, Research Associate Professor of
Civil Engineering, for his valuable contribution in the research regarding this thesis.
I consider myself to be extremely fortunate to have some good friends who
encouraged me to complete this thesis with reassuring inspiration and help.
11
TABLE OF CONTENTS
ACKNOWLEDGEMENTS ii
ABSTRACTS vi
LIST OF TABLES vii
LIST OF FIGURES ix
CHAPTER
1. INTRODUCTION 1
1.1 General Introduction 1
1.2 Constructibility: General Overview 2
1.3 Economic Analysis: General Overview 3
2. LITERATURE REVIEW 5
2.1 Introduction 5
2.2 Approaches in Practice for Constructibility Review 6
2.3 Constructibility Approach Suggested in NCHRP Report 391 6
2.3.1 Constructibility Review: Its Definition 7
2.3.2 General Purposes and Benefits of Constructibility Review 8
2.3.3 Appropriate Time to Apply Constructibility Review 9
2.3.4 Level of Formalizing Constructibility Review 9
2.3.5 Process Approach to Constructibility Review 11
2.3.5.1 Proj ect Development Process (PDF) Framework 11
2.3.5.2 Consctructibility Review Process (CRP) Framework... 12
2.3.5.3 Integration ofCRP into PDF 12
2.3.6 Constructibility Review Tools 14
2.4 Army Corps of Engineers' Approach for Constructibility Review 14
2.4.1 Introduction 14
2.4.2 Definitions and Purposes of BCOE Review 16
2.4.3 Guidelines for implementing BCOE review 16
2.4.4 Responsibilities Involved with Issuing A Certification for Finalized BCOE Review 18
111
2.5 Conclusions 18
CONSTRUCTIBILITY REVIEW 22
3.1 Constructibility Review Team 22
3.2 Development of the Work Breakdown Structure (WBS) 23
3.3 Equipment 24
3.3.1 Trench Excavators 24
3.3.2 Trench Support System 30
3.3.1.1 Drag Box 31
3.3.1.2 Trench Box 31
3.3.3 Earth Moving Equipment 36
3.3.4 Compaction Equipment 36
3.3.5 Weight of Equipment 37
3.4 Deficiencies in Draft Specification 40
3.5 Minimum Trench Width Requirements 40
3.6 Types of Backfill Materials 45
3.7 Granular Backfill Gradation 46
3.8 Minimum Cover 47
ECONOMIC ANALYSIS 50
4.1 Overview 50
4.2 Review of Information from Other States 53
4.2.1 Introduction 53
4.2.2 Economic Impact from the Acceptance of HDPE as a Biddable Altemative 54
4.3 Comparison of HDPE and RCP As-installed Cost Based on Analysis Performed with 'PipePac 2000' 59
4.4 Economics: State of Texas 60
4.4.1 Introduction 60
4.4.2 Pipe Price 63
4.4.3 Backfill Material Price 65
4.4.3.1 Overview 65
IV
4.4.3.2 Data Collection 69
4.5 As-installed Costs ofHDPE and Concrete Pipe 78
4.5.1 Sources of Data and Assumptions Made for Model Project Analysis 79
4.5.2 A Comparative Review on Findings of Model Project Estimation for Competing HDPE and RCP 81
5. CONCLUSION 91
5.1 Introduction 91
5.2 Conclusions 92
5.2.1 Conclusions: Constructibility Review 92
5.2.2 Conclusions: Economic Analysis 93
5.3 Recommendations 94
LIST OF REFERENCES 96
APPENDICES
A. DRAFT SPECIFICATION DATED MAY 1998 98
B. REVISED SPECIFICATION DATED AUG 1999 104
C. TYPES OF BACKFILL MATERIAL ECONOMICALLY AVAILABLE IN THE DISTRICTS OF TEXAS I l l
D. WORK BREAK-DOWN STRUCTURE: ITEMIZING MAJOR ACTIVITIES 115
E. ESTIMATING AS-INSTALLED COST OF HDPE AND RCP PIPE 121
ABSTRACT
This thesis documents the findings from a constructibility review and an
economic analysis for the installation of large diameter High Density Polyethylene
(HDPE) pipe for gravity flow storm drainage. Pipes of diameter 18 in., 24 in., 30 in., 36
in., 42 in. and 48 in. have been considered in the above analysis. The constructibilty
review and the economic analysis described here were performed as a part of a research
project that was sponsored by Texas Department of Transportation (TxDOT). A draft
specification was developed for HDPE pipe installation as the primary objective of the
above research project. Deficiencies in several areas of the draft specification were
figured out through a formal constructibility review approach that have been documented
in this thesis. Revised recommendations are incorporated into the final specification on
four areas: minimum trench width requirements, addition of cement stabilized backfill as
a new backfill type, gradation requirements for granular backfill, and minimum cover
requirement above the pipe crown. Large-diameter HDPE pipe is prone to flexural
deflection and it withstands the load exerting on it by the structural integrity of the pipe-
soil systerm. Revised recommendations were made with a view to conduct high quality
installations with HDPE pipe with suitable backfill materials. Any quality improvement
though constructibility review involves extra money. Therefore, the economic analysis
part of this thesis analyzed the economics ofHDPE pipe installation projects with respect
to installation with other traditional pipe products, such as RCP and CMP. The analysis
resulted in a comparative picture between HDPE and RCP from the viewpoint of
economics. However, all the cost figures used in this analysis were present value of the
resources. Significant savings was estimated from using HDPE over RCP under many
resource availability conditions. Despite the stringer installation requirements ofHDPE
pipe compared to RCP, analysis of data from real projects and hypothetical projects
showed that HDPE pipe can be cheaper if some locally available suitable backfill
material can be procured to the project site at a reasonable cost.
VI
LIST OF TABLES
3.1 Constructibility Review Team 23
3.2 Itemizing Major Activities 25
3.3 Minimum Digging Depth 30
3.4 Backhoe's Operating Weight 31
3.5 Equipment weight 39
3.6 Minimum Trench Width Recommendation in Various Specifications and Suggested by Various Pipe Manufacturers 42
3.7 Minimum Trench Width to Use Compactors 44
3.8 Minimum Trench Width 44
3.9 Gradation Requirements for Type III Backfill Material 47
4.1 Impact on Average Unit Bid Price of RCP when HDPE was Permitted to Bid as Experienced by SCDOT, 1996-1997 55
4.2 As-installed Cost Comparison for Different Pipe Materials 57
4.3 Percent Saving due to Presence of HDPE in the Bidding Process 59
4.4 As-installed Cost ofHDPE and RC Pipe Estimated by Using 'PipePac 2000'
and Savings from HDPE 62
4.5 Typical Smooth Interior Wall Corrugated HDPE Pipe Pricing (May, 1999)... .63
4.6 1998 Price of ASTM C-76 Class III RC Pipe (Supplied from San Antonio Plant, Manufacturer I) 66
4.7 Price of ASTM C-76 Class III RC Pipe (Supplied from Dallas/Fort Worth Metro Area Plant, Manufacturer I) 66
4.8 Price of ASTM C-76 Class ffl RC Pipe (Supplied from Dallas/Fort Worth Metro Area Plant, Manufacturer II) 67
4.9 Delivery Zones by County (Deliveries from Dallas/Fort Worth
Plant ofRCP Pipe, Manufacturer II) 67
4.10 Economically Available Granular Material in Texas 71
4.11 Overall Average Bid Price of Flowable Fill in Texas Districts, 1999 72
4.12 Overall Average Bid Price of Cement Stabilized Backfill in Texas Districts in 1999 74
4.13 Different Price Category of Cement Stabilized Backfill in Different Parts of Texas 75
vii
4.14 Overall Average Bid Price of Flex Base 77
4.15 Suitable Backfill Materials Selected for HDPE Pipe As-installed Cost Estimation 78
4.16 Estimated As-installed Cost of HDPE and RCP 84
4.17 Percent Estimated Saving from Using HDPE 89
C. 1 Types of Backfill Materials Economically Available in the Districts of Texas 112
D. 1 Work Breakdown Structure: Itemizing Major Activities of Pipe Installation Projects 116
E.l Estimating As-installed Cost ofHDPE and RC Pipe 122
Vlll
LIST OF FIGURES
2.1 The Effect on Cost due to Incorporating Constructibility Review at Different Stages of Project Life Cycle 10
2.2 First Two Levels of Typical PDP Framework 13
2.3 First Two Levels of Typical CRP Framework 13
2.4 Incorporating CRP into PDP 15
2.5 Items Addressed for Biddability and Constructibility 20
2.6 Items Addressed for Operability 20
2.7 Sample of BCOE Certification 21
3.1 Flowchart for Selection of a Trench Support System 32
3.2 Drag Box Installation 33
3.3 Trench Box Module 33
3.4 Pipe Installation with Trench Boxes 34
3.5 Pipe Installation with Slide Rails 35
3.6 Vibratory Plate Compactor and Impact Rammer 38
3.7 Comparison of Some of the More Commonly Used Trench Width Guidelines 43
3.8 Excerpts from Draft Specification that Address Minimum Cover Requirements 49
4.1 Percent HDPE Pipe Used by NY State DOT in Recent Years 61
4.2 Unit Pipe Price Comparison in Texas: HDPE versus RC Pipe 68
4.3 Price Zones of Cement Stabilized Backfill in Texas 76
4.4 As-installed Cost of RCP at Varying Pipe Price Conditions 85
4.5 Estimated As-installed Cost of HDPE versus As-installed Cost of RCP For Different Resource Price Conditions 86
4.6 Estimated As-installed Cost ofHDPE versus As-installed Cost of RCP For Different Resource Price Conditions 87
4.7 Estimated As-installed Cost ofHDPE versus As-installed Cost of RCP For Different Resource Price Conditions 88
IX
CHAPTER 1
INTRODUCTION
1.1 General Introduction
This thesis documents the findings from a constructibility review and an
economic analysis for the installation of large diameter High Density Polyethylene
(HDPE) pipe for gravity flow storm drainage. Pipes of diameter 18 iiL, 24 iiL, 30 irt, 36
iiL, 42 in. and 48 in. have been considered in the above analysis. The constructibilty
review and the economic analysis described here were performed as a part of a research
project that was sponsored by Texas Department of Transportation (TxDOT). The
primary objective of the above research project was to develop standard specifications for
the installation of large diameter High Density Polyethylene pipe for gravity flow storm
drainage. In 1993, TxDOT introduced special specification No.4296: "Thermoplastic
Pipe" (1993) that enabled the use ofHDPE pipe of up to 36 inch diameter in TxDOT
construction projects. Because HDPE is flexible pipe, its performance criteria are
different from those of rigid pipe. The strength of flexible HDPE pipe is the result of the
pipe-backfill integrated system, whereas concrete pipe withstands most of the imposed
loads because of its rigid structural strength. Due to these special characteristics of the
HDPE pipe-soil system, a high quality installation, specifically proper backfilling around
the pipe, needs to be assured. Therefore, as a means of quality control during the
installation of thermoplastic pipe, it is customary to measure pipe deflection after its
uistallatioiL However, OSHA requirements for confined space safety prohibit
departmental or contractor personnel entering pipe to measure deflectiorL TxDOT
special specification No. 4269 allowed the use of two types of backfill materials in the
pipe embedment zone; Type I: Flowable backfill and Type II: Granular backfill.
However, in March 1996 TxDOT decided to remove the requirement to measure pipe
deflections and at the same time decided to require flowable backfill in all installations
regardless of the location with the exception of side roads and driveway culverts (Source:
Special Provision and/or Specification Change Memorandum from Wilson, Robert, dated
March 15, 1996). Unfortunately, flowable fill is the most expensive of all backfill
materials. Consequently, when flowable fill was used, the high cost of backfill ofl&et any
economic benefits that could have been gained by using comparatively cheaper HDPE
pipe. This situation led TxDOT to initiate a comprehensive research study with the
specific objective of finding alternate, cheaper backfill materials for HDPE pipe
installation. Research work was completed during the initial phase of the above research
project (i.e., from September 1997 to May 1998) resulted in a draft specification that
documented recommendations for a quality installation ofHDPE pipe v^th diameter
ranging from 18 in. to 48 in. This draft specification, dated May 15, 1998 is found in
Appendix A of this thesis. The next step in this research was to perform constructibility
review on the above draft specification to ensure that the pipe installation according to
the specification can be accomplished in the field v^thout difficulty. Difficulties can
arise during the field implementation due to ambiguities in the specifications, contractors'
lack of familiarity with construction methods specified, non-availability of special
construction equipment required, non-availability of specified material within economic
distances, levels of quality that are unrealistically high to be achieved in the field, etc.
The various steps taken in completing the above constructibility review is fiilly described
in this thesis. Constructibility review, which is one of the two key topics of this thesis,
involves quality eissurance during HDPE pipe installation. Secondly, one of the primary
incentives for the use ofHDPE pipe is the economic benefit to be gained from the
cheaper material cost as well as faster installation. However, on the other hand, this type
of pipe requires special types of backfill materials other than native soil and therefore
must be obtained at a cost. Therefore, economics of pipe installation is an irr^rtant
aspect that must be examined in the selection of backfill materials. Accordingly, the
second topic that is addressed in this research involved a detailed economic analysis
related to HDPE pipe installation in Texas. The followdng two sections provide a general
overview of this project-specific constructibility review and economic analysis. They
also describe how the other remaining chapters of this thesis have been organized.
1.2 Constructibility: General Overview
Once the importance of performing a constructibility review for the HDPE pipe
installation was acknowledged by the researchers, then it was necessary to prepare a work
plan to accomplish this task. As a first step toward the goal, the existing formalized
approaches for detailed constructibility review were examined as a part of the literature
survey. The findings from this task are documented in Chapter 2 of this thesis. Based on
the above literature survey, constructibility strategy for HDPE pipe installation was
begun. The first step in this process was to form a constructibility review team. The
entire constructiblity review is described in detail in Chapter 3. The input needed for
constructibility was obtained through a number of sources. Contractors who are
experienced with this kind of pipe installation project were contacted in order to receive
input from their professional experience. Members of the TxDOT project monitoring
committee also made inq)ortant contributions to this process by pointing out some
implementation ambiguities in the presented draft specification. Eight TxDOT pipe
installation projects that were located in difierent districts of Texas were selected and
their installations and post-construction performance were monitored throughout the
project duration. Additionally, observations from a series of on-campus tests were used
in constructibilty review.
An important objective of this research was to find alternate backfill materials in
order to avoid using flowable fill. The gradation characteristics of several granular
backfill materials have also been examined in Chapter 3 as a part of this constructibiltiy
review. The suggestion from district laboratory engineers was the primary source of
information on readily available backfill materials in Texas. A revised specification
dated August 16, 1999, included all the modified recommendations on trench dimensions
and backfill materials that was obtained through constructibility review performed in
Chapter 3. This revised specification is found in Appendbc B of this thesis.
1.3 Economic Analysis: General Overview
One of the important issues related to the acceptance of HDPE pipe as a biddable
altemative for large diameter storm drainage systems is whether HDPE pipe can compete
economically against two other pipe products that have been in use in construction for
many years, namely reinforced concrete pipe and corrugated metal pipe. Since it is
important to ensure a very good quality pipe-soil structural system when installing HDPE
pipe, its installation generally requires more expensive backfill materials and extra care
during backfilling. The draft specification does not allow the native soil as backfill
material for HDPE pipe, whereas reinforced concrete pipe can be backfilled by native soil
without spending any extra money for purchasing and transporting special backfill
material. This is an important cost issue involved in installation of HDPE pipe. On the
other hand, price of concrete pipe or corrugated metal pipe delivered at the site is much
higher than that of HDPE pipe. Also, handling the heavier concrete pipe involves more
labor and longer project duration compared to the lighter HDPE pipe. Longer project
duration involves extra cost. Thus, each kind of pipe material has relative advantages and
disadvantages from an economic point of view. In Chapter 4 of this thesis, all the factors
affecting the cost of the pipe installation are discussed in great detail. In this chapter an
economic analysis was performed to compare HDPE pipe with reinforced concrete pipe
and corrugated metal pipe from the standpoint of installation cost. Chapter 4 begins with
information that were collected from others state DOTs providing a comparative
overview of as-installed costs for HDPE pipe versus other pipe products. Secondly, the
price information for various resources involved with pipe installation, specifically the
price of backfill material and the price ofHDPE and reinforced concrete( RC) pipe within
various parts of Texas are documented. For this purpose, leading manufacturers and
suppliers of the resources were contacted through phone, fax and email. This information
is presented in Chapter 4 in a comparative manner. It shows the availability and
comparative price of important resources involved in HDPE pipe installation, as well as
installation with other competing pipe materials, specifically in Texas districts. With the
help of this actual resource price information, as installed costs of several model projects
(using HDPE and RC pipe) have been calculated. The estimates of those model projects
were synthesized parametrically. The three parameters chosen were pipe diameter, pipe
price and backfill material price in different districts of Texas.
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
The importance of incorporating constructibility review into the processes of
HDPE pipe installation was introduced briefly in Chapter 1. As a continuation of that
introduction on constructibility review, this chapter mainly discusses available
approaches for project level constructibility review as a part of the literature review for
this thesis. Prior to starting on the approaches in practice for constructiblity review, this
section examines why HDPE pipe installation projects need a formal approach for
construcitiblity assessment. Consequently the following sections drew focuses on
available literature about formal approaches of constructibility review.
Constructibility review is a very recent concept. It was previously conceived as
an informal approach for improving project development process until a few years ago.
Most projects have some kind of informal constructibility review that does not follow any
well-organized review pattem or incorporate any constructibility review persoimel. But
when a big budget project has alternatives in the context of choosing various resource
options based on performance and economy, a formalized approach may be a key-tool for
successfully implementing a project using certain preferable resources. In the previous
chapter it was revealed that HDPE pipe has two other broadly accepted altemate pipe
materials that creates a competitive environment for large diameter gravity flow storm
drainage pipe installation projects. These are Reinforced Concrete Pipe (subsequently
referred to as RCP) and Corrugated Metal Pipe (referred to as CMP). One vital point
about using different pipe materials is that the construction processes that involve the
installation with different kinds of pipe are not all the same. Hence, developing a new
specification for installation of large diameter HDPE pipe was the leading part of this
research project. In the process of developing that specification it was perceived by the
researchers that construction processes ofHDPE pipe installation are critical to some
extent compared to that of other pipe, such as RCP and CMP. This is because of flexural
nature of large diameter HDPE that might cause flexural deflection in future. The
researchers finally came up with performing a constructibilty review that was performed
on the draft specification rather than on any specific construction projects. The following
sections, perceptively, skimmed though the relevant literatures on constructibility review.
2.2 Approaches in Practice for Constructibilitv Review
Among the existing approaches a comprehensive model for formalized
constructibility review is suggested in the NCHRP report 391, "Constructibility Review
Process for Transportation Facilities," prepared by Anderson and Fisher (1997). Another
approach practiced by the U.S. Army Corps of Engineers supports the BCOE
(biddability, constructibility, operability, and environmental review) aspects of a project
(USAGE, 1994). In order to incorporate a formalized constructibility review approach
into HDPE pipe installation, and to set up objectives and plans for it, botii
constructibility approaches will be discussed here as a part of the literature review for this
thesis.
The following two sections summarize the ideas and guidelines presented in
these two models.
2.3 Constructibilitv Review Approach Presented in the NCHRP Report 391
NCHRP Report 391, "Constructibility Review Process for Transportation
Facilities," is a formal and comprehensive project level workbook for performing
constructibility review. This model will be presented here as a part of essential literature
review for this thesis that will lead us to incorporate some concepts of this model into the
constructibility review process ofHDPE pipe installation projects. The main objective of
this workbook is to show guidelines on how to improve highway-construction-project
contract documents, to ensure rational bids and to minimize problems during
construction. The workbook contains two stand-alone sections. The user of the book
might want to choose any or both the sections as a background depending on the
characteristics of the project needed to be reviewed. Presumably, HDPE pipe installation
projects have their ovm project level difficulties that might arise during its construction
phase because of the flexural nature of lightweight HDPE pipe. Section I illustrates the
framework of constructibility review process presented in this workbook. Section II
demonstrates implementation details of constructibility review process. However,
Section I, the overview, was of prime interests for this research in order to set up a plan
for constructibility review ofHDPE pipe installation. The whole concept presented in the
workbook is summarized here under some key-phrases and only those parts of it is
presented with emphasis which might be helpful to figure out a plan for the
constructibility review ofHDPE pipe installation. More specifically, the key-concept of
this formal and comprehensive approach for constructibility review is how a Project
Development Process (PDP) interacts with and gets benefited from the Constructibility
Review Process (CRP). In any way, the particulars of constructibility review guidelines
presented in this workbook can be described under the following terms.
a. Constructibility review: its definition;
b. General purposes and pay backs of constructibility review;
c. Appropriate time to apply constructibility review;
d. Level of formalizing constructibility review;
e. Process approach to constructibility review;
f Constructibility review tools.
The following sections will reveal that inherent concept of this formalized
constructibility review model.
2.3.1 Constructibilitv Review: Its Definition
Constructibility review is defined in the NCHRP Report 39las follows:
"Constructibility is integration of construction knowledge and experience in
planning, design, procurement and field operations to achieve overall project objectives"
This definition simply means that constructibility review is the integration of
construction knowledge and experience into planning, design and construction phases of
a project. Report 391 emphasizes on looking for and apply construction knowledge and
experience and to store this information in an appropriate format for easy retrieval. This
is a proactive mechanism that will improve outputs of planning and design processes and
end up with efficiency of construction. Constructibility practices should be made an
integred part of the project development process through some level of formalization.
2.3.2 General Purposes and Benefits of Constructibilitv Review
If construction knowledge and experience can be incorporated into an improved
project development process through constructibility review, generally it can bring the
following benefits:
a. Reduced costs,
b. Shortened schedule,
c. Improved project quality and safety,
d. Enhanced management of risk,
e. Increased customer satisfaction,
f Constructibility pays for itself.
Implementation of constructibility requires extra time, money and people.
Evidences indicate that constructibility pays for itself by reducing project costs. In 1992,
the Arizona DOT established a Constructibility Engineer position. This person has an
extensive background both in design and construction. Plans and specifications are
reviewed by this person to determine possible improvements from a constructibility
perspective. The savings achieved as a result of constructibility improvements amoimted
to 1.7% of the total cost of the six projects (approximately $68 million). The expense of
the review was such that the benefit to cost ratio was twenty five to one. That is, for
every dollar spent reviewing these projects for constructibility, Arizona DOT saved $25.
Additional benefits identified in Report 391 can be quoted here as follows:
a. Engineers, through constructibility review programs, can be trained more
quickly, thus providing better decision-making, support data and knowledge.
b. The probability of successful project schedule performance increases
substantially with a formal constructibility program especially on fixed-price
contracts.
c. The intangible benefits which include higher productivity, better schedules and
sequence of construction, enhanced quality, lower maintenance, safer jobs, and
more safety and convenience for the traveling public should also be recognized.
2.3.3 Appropriate Time to Apply Constructibilitv Review
Fig 2.1 demonstrates a very important and observable criteria that has to do with
appropriate timing of applying constructibility review. In the life cycle of a project
implementation a project usually goes though the general steps of planning, design,
bidding, pre-construction meeting, construction, operation and maintenance. Fig. 2.1
shows that maximum benefit can be achieved if the effective use of construction
knowledge and experience can be incorporated during the early stages of planning and
design. This is because the ability to influence cost through changes in project plans and
design is maximum during these early stages. The research proposal for developing a
new specification for HDPE pipe installation, advantageously, had included the idea of
performing constructibility review well ahead of the time when the research started.
Unfortimately, agencies seem to rely heavily on the construction expertise of
design personnel, who are well versed in such technical issues as design standards and
codes, but who lack expertise in field construction methods and techniques. This
approach reduces the likelihood of getting benefits from applying constructibility review
at the appropriate time. This is actually an informal approach of performing
constructibility review conceived by most transportation agencies. The section below is
about level of formalization required when applying constructibility process.
2.3.4 Level of Formalizing Constructibility Review
Depending on project complexity, constructibility review process can be
categorized into three level of formalization : Informal, semiformal and formal.
Constructibility is given minimal attention during project planning and feasibility during
design reviews. Construction expertise is frequently not accessed during the plarming
and design process. The research associated with the development of the NCHRP Report
391 shows that only 23 percent of state agencies have formal, documented
constructibility programs. Also, the level of formality of these programs varies. Several
programs are somewhat formal, as they incorporate constructibility concepts suggested in
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the literature such as specifying constructibility objectives, forming a constructibility
team, determining the level of formality, and mechanisms to obtain constructibility input.
Less formal programs often use checklists, with input obtained only at definite points in
the design process where reviews take place. While interest in formalizing
constructibility reviews is growing, even the most formal constructibility programs
appear to lack distinct functions and steps that lead the project personnel through
implementation process. Formalization of the Constructibility Review Process
(designated as CRP) must tap the right expertise and information when and where needed
to achieve maximum benefits.
2.3.5 Process Approach to Constructibility Review
A process approach to implementing constructibility at the project level is
presented in the NCHRP Report 391. This approach consists of describing the process at
a microscopic scale, ultimately focusing on functions, steps and tools essential to conduct
a project level Constructibility Review Process (CRP). At this level CRP acts on outputs
from the Project Development Process (PDP) in order to provide constructibility
improvements that are incorporated into planning and design docimients. In the
following sections CRP and PDP will be defined and incorporated together to create the
skeleton for constructibility review.
2.3.5.1 Proj ect Development Process (PDP) Framework
Projects are developed through a process described as the Project Development
Process which typically consists of three main phases:
1. Planning
2. Design
3. Construction
Each phase is further divided into an increasing level of detailed activities. This
continuing breaking down of a project into several levels of hierarchy makes the PDP
frame work. The activities at upper levels of the framework are considered generic and
are typical of most project development processes. However every state agency will have
11
its own unique PDP. The first two levels of a typical PDP framework have been shovm
in Fig. 2.2 by branching each phase into sub-phases and each sub-phase into more
detailed project activities that involve specific man power, equipment, and other
resources. For example. Preliminary Design, a sub-phase of Design Phase presented in
Fig. 2.2, has been divided into eight detailed project functions at the third level of the
framework. In the same manner, other sub-phases of three major phases of PDP
framework needs to be divided into relevant activities. This third level of the framework
is of prime interest from the viewpoint of constructibility review where necessary
modification and improvement can be made to achieve project goals.
2.3.5.2 Consctructibility Review Process (CRP) Framework
CRP is applied during the planning, design, and construction phases of a project.
Quite analogous to PDP framework described in the previous section, the CRP is divided
into increasing levels of detailed constructibility functions. As outlined in Fig. 2.3 the
first two levels of the CRP framework imitate the PDP phases and sub phases. The third
level which is derived from the second level of hierarchy represents the proposed
individual constructibility functions that are performed during project development.
This level is where activities occur in order to integrate construction knowledge
and experiences into the PDP. In Fig 2.3 only 'Design Phase' has been divided into
detailed constructibility functions at the third level of the framework. In a similar
fashion other two major phases. Planning Phase and Construction phase, can be
disintegrated into detailed constructibility functions up to the third level in the
framework.
2.3.5.3 Integration ofCRP into PDP
As shovm in Fig. 2.4, integration of construction knowledge and experience into
the PDP necessitates iterative, recursive exchange of information between the PDP and
the CRP. Project information from PDP flows to CRP, which then takes this
information, acts on it, and retums suggested improvements for incorporation into
planning and design. Each set of constructibility functions has a specific objective. To
12
AOP: Project Development Process AlP: Planning Phase
A l lP : Project Definition A12P: Concept Plan Development
A2P: Design Phase A21P: Preliminary Design
A211P: Design Criteria/Para meters A212P: Survey Utilities/Locations/Drainage Area A213P: Design Concept/Conference A214P: Geotechnical Studies A215P: ROW Development A216P: Geometric Alignment A217P: Bridge Layouts A218P: Permits/Agreementa
A22P: PS&E Development A23P: Final Design
ASP: Construction Phase A31P: Pre-Construction Phase
A32P: Construction A33P: Post-Construction
Fig. 2.2: First Two Levels of a Typical PDP Framework.
(Source: Anderson and Fisher(1997), NCHRP Report 391. pp. A0.8)
AO: Apply Constructibility to Transportation Projects A l : Apply Constructibility during Planning Phase
A l l : Apply Constructibility during Project Definition A12: Apply Constructibility during Concept Plan Development
A2: Apply Constructibility during Design Phase A21: Apply Constructibility during Preliminary Design
A211: Modify Constructibility Team A212: Finalize Project Constructibility Procedure A213: Consult Lessons Learned to Design
A22: Apply Constructibility during PS&E Development A221: Evaluate Plans &Speciflcations A222: Validate Constructibility Improvement A223: Review and Approve Constructibility Improvements
A23: Apply Constructibility during Rnal Design A224: Summarize Constructibility Improvements
A3: Apply Constructibility during Construction Phase A31: Apply Constructibility during Pre-Construction Phase A32: Apply Constructibility during Construction A33: Apply Constructibility during Post-Construction
Fig. 2.3: First Two Levels of a Typical CRP Framework.
(Source: Anderson and Fisher(1997), NCHRP Report 39 L pp. A0.9)
13
achieve these objectives, inputs from the PDP and from a preceding set of
constructibility functions are essential. In the same manner, outputs from performing
each set of constructibility functions return information to the PDP and to the next set of
constructibility functions. This cyclic process between the CRP and PDP continues as
long as the project proceeds through each phase. Fig. 2.4 illustrates the basic structure
of implementation guidelines for constructibility review presented in the NCHRP Report
391.
2.3.6 Constructibility Review Tools
NCHRP report 391 lists a set of constructibility review tools and describes their
characteristics and usage recommended to perform individual actions for each
constructibility functions. Future tools, that is, those tools having potential applications
in the future for an advanced CRP, are also listed. Some of these tools are listed below.
a. Constructibility meetings
b. Suggestion forms
c. Pre-bid conference
d. CPM (critical path method)
e. Benefit-cost analysis, etc.
2.4 U.S. Army Corps of Engineers' Approach
2.4.1 Introduction
U.S. Army Corps of Engineers (1994) established a regulation No. 415-1-11 titled
as 'Biddability, Constructibility, Operability and Environmental (BCOE )' in the
regulation no. 415-1-11. It has been docimiented in 8 sections. Section 1, 2, 3 and 4
describes the purposes, applicability, references used, and definitions respectively
concerning the BCOE aspects presented in this regulation. Section 5 briefly gives a
general overview of the concept. Section 6 occupies major portion in this regulation that
illustrates the implementation guidelines of BCOE aspects. Section 7 and 8 specifically
lists the designations of appropriate personnel and their responsibilities needed to make
BCOE review official and issue certification.
14
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BCOE concept established by U.S. Army Corps Of Engineers has been presented
in the subsequent sections under the following sub-titles.
a. Definitions and purposes of BCOE review,
b. Guidelines for implementing BCOE review,
c. Responsibilities involved in making BCOE review official.
2.4.2 Definitions and Purposes of BCOE Review
The terms of BCOE aspects followed by U.S. Army Corps Engineers (1994) are
defined as follows:
Constructibilty and biddability are defined as ease with which a designed project
can be built and the ease with which the contract documents can be imderstood, bid
and, administered and executed. Operability refers to the ease with which a project
ca be operated and maintained. Environmental review refers to the protection of
air, water, land, animals, plants and other natural resources from the effects of
construction and operation of the project as stated in the Environmental Impact
Statement or Assessment.
The above definition of constructibility and biddability suggests to make the
contract documents comprehensive enough after the review is done so that it can be bid,
administered and implemented with clarity. Definitions of operability and environmental
review demonstrate their general purposes as stated above.
In short the purpose of this regulation is to consider BCOE aspects during design
and integrating a high degree of BCOE review into construction procurement for aU
projects.
2.4.3 Guidelines for Implementing BCOE Review
This is the kernel part of the BCOE concepts that is divided into three sub
sections: The following paragraphs briefly present the contents of this three sections.
Section 6(a) demonstrates the guidance to perform a BCOE review. This section
describes how to incorporate reviews at diSerent stages of a project by maintaining
proper timing and assuring that right person is involved in the review process. The
16
ultimate goal of BCOE review described in this section is to prepare a review document
that will serve as the basis for the certification required as stated in section 7 of the
regulation. People required for reviews and to improve BCOE aspects of designs include
construction, engineering, project management, and operations personnel from division
and district offices. Constructions and operation personnel from districts who are familiar
with project location and site related problems and have the potential to understand
design assumptions and specification, shall participate in the reviews. Input from
construction and operation personnel is desirable during both the following stages of the
project.
a. Early enough in the design process to allow its incorporation during design
development.
b. After final design and coordination reviews when the entire contract document
is ready for advertisement, but sufficiently prior to advertisement to allow for
corrections.
Therefore, in order to ensure appropriate timing of review, a minimimi of two
specific reviews are required to be performed by these personnel. The first will be made
at the concept stage when design process cannot be stopped and after the design is
sufficiently complete for substantive comment. The second will be made at final design
stage with complete specifications including special clauses at least 30 days prior to
advertisement. An additional review will be required once the design is completed and
reviewed that will be released to the prospective bidders after an abeyance period of six
months. The area/resident office shall transfer the comments to design branch though the
Automated Review Management system (ARMS). A BCOE back-check review for
certification required by Section 7 of the regulation is required by Engineering and
Construction Division prior to bid opening. All necessary comments shall be incorporated
in that final check prior to include it in the bid package.
Section 6(b) addresses the probable items and fimctions to be undertaken in
biddability and constructibility reviews that are supposed to be performed by Area
Engineer, Resident Engineer and Construction Staff personnel. Fig. 2.6 is an extract
from original regulation of U.S Army Corps of Engineers that lists 11 items/functions
17
addressed for biddability and constructibility reviews. In a similar fashion section 6(c) of
the regulation presumably lists 10 items for operability reviews which is presented in
Figure 2.7 below as an excerpt form original regulation. However, the items to be
addressed for reviews will not be limited to the functions listed in these two sections.
2.4.4 Responsibilities Involved with Issuing Certification for Finalized BCOE Review
The following officials bear the responsibilities for the accomplishment of
finalized BCOE review and have the certification for it.
a. Chiefs of Project Management has two responsibilities: (i) to ensure that
sufficient time for the BCOE reviews illustrated in Section 6.a is included in the project
baseline schedule and (ii) to ensure adequate design funds for the success of BCOE
reviews in the baseline budget.
b. Chiefs of Engineers will provide documents for review and back check,
evaluate comments, and provide feedback on disposition of comments. The main
responsibilities can be quoted as follows from the original regulation:
c. Responsibilities of Chiefs of Construction can be quoted as follows:
"The Chief of Construction or a duly authorized representative. Branch Chief or
higher, will certify, in writing that all appropriate BCOE comments have been
incorporated in the bid documents or satisfactorily resolved and that feed back has been
provided to reviewers for all comments."
d. Figure 2.8 below is a sample certification required to be signed by the Chief
of Engineering Division and the Chief of Construction Division as described above. This
has been attached with the original regulation as Appendix A. As stated in the regulation,
"Chiefs of Contracting will ensure that bid opening is not made prior to the above
certification unless the contracting officer determines that it is in the best interest of the
government to award without incorporation of all comment."
18
2.5 Conclusions
This chapter presented the available literature on constructibility review which
will serve as a background for Chapter 3. Consequently, Chapter 3, which performs a
constructibility review on the draft specification, starts with planning a constructibility
review strategy. Some of the concepts for performing a formalized constructibility
review presented in the previous sections have been incorporated in to the constructibility
plan. One such concept perceived from two models presented here is that some
personnel with specific responsibilities are required to be involved in this kind of review.
Therefore, a constructibility review team with specific responsibilities was constructed as
a part of a formal constructibility review strategy. The concept of breaking down a
project into detailed project activities as stated in a previous section as PDP/CRP
framework was applied at the beginning of the review in Chapter 3. However, no
literature review has been provided for economic analysis conducted in Chapter 4. It was
actually performed with a generic approach based on present-value-cost-data.
19
b. Items to be addressed in biddability and constructibility reviews performed by the Area engineer, Resident Engineer, and Construction Staff personnel will include, but not be limited to: (1) Accurate depiction and adaptation of design structures and features to site conditions and
restrictions such as access, utility availability, drainage, storage, existing underground utilities and general configuration.
(2) Appropriateness of contract sequencing, relationship to other work, contract performance time, contractor quality control (QC), submittal requirements and network analysis system provision for the specific project.
(3) Adequacy of working area and storage space and access for all site contractors as well as provisions for coordination to preclude on-site conflicts.
(4) Clarity, simplicity and essentiality of the bid schedule. (5) Local availability of special materials and labor skills. (6) Have special installation requirements been addressed? (7) Are the drawings and specifications free form ambiguities? (8) Are essential details and proper verbiage included ? (9) Do the specifications address the impact of the construction on the environment? Is the
contractor required to submit an environmental plan addressing how he will mitigate water, air, soil and noise pollution?
(10) Do the drawing depicts the site environment? Will the project encroach upon wetlands or endangered species habitat? Is erosion control adequately addressed?
Fig. 2.6 : Items Addressed for Biddability and Constructibility
(Source: U S. Army Corps. Of Engineers (1994), Regulation No. ER 415-1-11, pp. 3)
c. Items of operability reviews to be addressed by the facilities engineer or responsible operations engineer personnel will include, but not limited to:
(1) Architectural compatibility with existing facilities and established base plan (2) Adequacy of size and configuration of proposed facilities to meet the expected function or
mission and inclusion of all necessary features (3) Compatibility of proposed installation and equipment with existing facilities for ease of
maintenance and replacement. (4) Adequate size of mechanical equipment and maintenance spaces to facilitate maintenance. (5) Ease of maintenance and upkeep of planning and landscaping. (6) Adequacy of position indicators on operating equipment. (7) Adequacy of periodic inspection capability and ability to accomplish periodic maintenance. (8) Provision of features for safe, efficient and economic operation including maximum energy
conservation. (9) Appropriate level of operation sensitivity and/or complexity. (9) Design provides for operations which will be environmentally safe.
Fig. 2.7: Items Addressed for Operability
(Source: U. S. Army Corps. Of Engineers (1994), Regulation No. ER 415-1-11, pp. 4)
20
SAMPLE CERTIFICATION
BCOE Certification
Project Tifle:
Specification Number:
Installation:
I certify that all appropriate biddability, constructibility, operability and environmental
comments received and reviewed by this office by (Date) have been
incorporated into the bid package. Feedback has been provided to reviewers for all
comments.
Date Chief, Engineering Division
Date Chief, Construction Division
Fig. 2.8 : Sample of BCOE Certification
(Source: U S. Army Corps. Of Engineers (1994), Regulation No. ER 415-1-11, pp. A-1)
21
CHAPTER 3
CONSTRUCTIBILITY REVIEW
The previous chapter presented a detailed discussion of constructibility review as
a concept and its applicability to general civil engineering field construction projects.
This chapter describes the application of these concepts to evaluate the practicality of the
draft specification that was developed previously in this research project. This draft
specification can be foimd in Appendbc A of this report. It was developed based on
guidance available through specifications developed by other agencies such as AASHTO,
ASTM and other state DOTs as well as data collected from experimental work conducted
in this research. The primary objective of constructibility review was to examine the
draft specification from a constructibility viewpoint and hence identify any elements in
the specifications that may create difficulties during its field implementation. The
various steps involved in the above constructibility review and the recommendations are
presented in the following sections.
3.1 Constructibility Review Team
As a first step in the constructibility review process, it was necessary to identify a
number of qualified individuals to serve on a constructibility review team. In a typical
field construction project, the constructibility review will be performed by individuals
who have significant field experience in the specific construction processes involved.
However, the constructibility review described here was difierent in a number of ways.
First, it did not involve a specific pipe installation project. Instead, it involved a new
specification that has been developed for such pipe installations. Secondly, the review
was performed as a part of a research project. Therefore, this constructibility review
team consisted of two groups of individuals: (1) members of the research team, (2)
individuals with experience in the field installation of HDPE pipe. The researchers
included: (a) research assistant charged with the primary responsibility of conducting the
constructibility review, (b) the research study supervisor of the study and (c) other key
investigators. The field construction personnel included (a) members of the TxDOT
22
project monitoring committee, (b) contractor representatives from TxDOT pilot
construction projects in San Angelo and Laredo districts and (c) representatives from
HDPE pipe manufecturing companies. The primary role of the researchers was to collect
necessary information from the field construction personnel, published literature, phone
survey, and latest estimating catalogs and then perform the review based on this data.
Table 3.1 below identifies the members of the constructibility review team.
Table 3.1 Constructibility Review Team
Researcher/s Field Personnel
Research Assistant TxDOT Project Director Mohd. D. Alam Victor Pinon, P.E.
Research Supervisor District Construction Engineers P.W. Jayawickrama, Ph.D.
Other Key investigators Representatives of the Contractors Involved in TxDOT D.G. Gransberg, Ph.D., P.E. Pilot Construction Projects S. Phelan, Ph.D., P.E.
Representatives from the HDPE Pipe Manufacturers
3.2 Development of the Work Breakdovm Structure (WBS)
Constructibility review begins with the development of a Work Breakdown
Structure (WBS) for the particular construction project. During this task, the pipe
installation process is analyzed in detail and each individual construction activity is listed
in a sequential manner. As a first step, the pipe installation process is divided into five
major tasks. They are:
1. Trench excavation,
2. Installation of trench support system,
3. Preparation of the trench bottom,
4. Laying and joining pipe,
5. Placement and compaction of backfill.
23
The next step involves the development of the detailed work breakdown structure.
In the detailed work breakdown structure, each task is divided into several sub-tasks.
Table 3.2 presents the above detailed work breakdown structure. It identifies all the steps
that the site engineer, contractor, and the construction crew must go through from the
time they receive the plans to the time of project completion. Table 3.2 also provides
information on the resources needed for the completion of each sub-task. These
resources include: equipment, construction crew and material. Subsequently, in Chapter
4 Economic Analysis, this work breakdown structure is fiirther expanded to include the
costs associated with each construction activity.
3.3 Equipment
As shovm in Table 3.2, one of the important resources needed for successful pipe
installation includes construction equipment. The construction equipment required for
each itemized work process, as listed in that table, include the following:
1. Trench excavators;
2. Trench support system: trench boxes, drag boxes, slide rails, trench sheeting;
3. Pipe-layers, cranes;
4. Backfilling equipment: loaders, backhoes, backhoe loaders;
5. Compaction equipment for initial backfill: vibratory plate compactors, impact
rammers;
6. Earth moving vehicles: elevating scrapers, belly-dump trucks.
The following sections provide a preview of the equipment listed above. The
discussion includes the selection of right type of equipment for each work process and
their effects on the installation process as a part of constructibility review
3.3.1 Trench Excavators
Backhoe is the most commonly used equipment for the excavation of pipe
trenches. It is used for excavating below the level of tracks and also as a small crane for
handling duties
24
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in pipe laying and installing trench support system. When excavating large and deep
trench, an operating plan should be sketched to suit the removal of the spoil and
accommodate any ramps needed for the trucks. Selecting an excavator of right capacity
is important to do the excavation job without any difficulty. Table 3.3 lists typical
maximum digging depth for hydraulic backhoes of varying capacity. Accordingly, the
maximum digging depth for a backhoe with % CY capacity is 18 ft (6m). In other words,
greatest construction efficiency may not be achieved if the above equipment is used to
excavate a trench with depth of say 25 ft (approximately 8m).
Table 3.3 Maximum Digging Depth
Bucket capacity y4CY-5/8CY y4 CY ICY 2 CY 2 CY 2'/2CY 3 CY (not heaped)
Backhoe's 5m 6m 7m 8m 8m 8!/2m 9m Maximum digging depth
Another important factor to be taken into consideration in the selection of the
appropriate excavation equipment is their operating weight. This is because any
equipment that traverses the already installed pipe has the potential to disturb the
structural integrity of buried HDPE pipe. This issue will be reviewed in a subsequent
section of this chapter where the minimum cover required for various axle loads. Table
3.4 below lists typical operating weights for backhoes of various capacity.
3.3.2 Trench Support Systems
Pipe installation projects may involve excavation to large depths. In such
projects, safety of the construction crew working inside the trench require special
attention. Safety must be ensured through the selection of a trench support system that is
appropriate for the specific depth of excavation.
30
Table 3.4 Backhoe's Operating Weight
Maximum bucket capacity Operating weight 0 . 8 2 C Y 27,910 lbs 0.97 CY 35,100 lbs 1.83 CY 50,000 lbs 2.12 CY 59,560 lbs 2.75 CY 73,880 lbs
3.40 CY 110,420Jlbs Source: Caterpillar Performance Handbook, Edition 26.
OSHA regulations(Standards -29 CFR) Part 1926 Subpart P, Standard no.
1926.652 provide guidelines that must be followed in this regard. These are presented
below in the form of a graphical flow chart.
According the OSHA flow chart presented above, some kind of trench protection
system is required whenever the trench depth exceeds 5 ft. Consequently, many large-
diameter HDPE pipe installations will require such trench support. The following section
presents some of the most commonly used trench support systems.. These include: trench
boxes, drag boxes, or wood plank and struts.
3.3.2.1 Drag Box
Fig. 3.2 shows how a drag box is utilized in construction. The method of
installation requires the trench to be cut slightly wider than the box and the drag box is
lowered into position. Subsequently, backfilling inside the drag box and excavation of
the next segment of the trench proceeds simulataneously. After the backfilling has been
completed, the drag box is pulled forward into position by a large excavator into the new
excavation.
3.3.2.2 Trench Box
Fig. 3.3 is a sketch of a trench box. It is a modular system composed of two
support walls separated by props. Fig. 3.4 demonstrates the method of installation of
31
Is the excavation more than 5 ft in depth?
Is there potential for no
Cave-in?^^
Is the excavation
^ entirely in stable
rock?
NO YES
• Excavation may be made with
Vertical sides
YES NO
^ Excavation must be sloped or shored ^
or shielded
f Sloping selected Shoring or shielding selected
Fig. 3.1 Flow Chart for Selection of a Trench Protection System
trench boxes. Contractors have generally found that three boxes are sufficient to operate
an efficient cycle of work - one box going down with excavating, a second box already
founded to provide protection for pipe installation and the third box coming up as the
backfilling proceeds.
Fig. 3.5 shows the use of slide rails in the installation of trench boxes. The trench
box system has been developed a stage ftirther to incorporate slide posts driven ahead of
the slide plates to act as guides. This method overcomes difficulties in trench box
withdrawal in granular soil.
32
STFENING PLATE P U l FROM EXCAVATOR
"Wirr
PIPE
Fig. 3.2: Drag Box Installation
Fig. 3.3: Trench Box Module
33
Fig. 3.4: Pipe Installation with Trench Boxes
34
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3.3.3 Earth Moving Equipment: Bulldozers, Loaders. Scrapers and Graders
The construction sites are often uneven and require leveling. When construction
takes place in such rough terrain, excavated material is removed, transported and
deposited in a cycle. There is a fairly broad range of earth moving equipment is available
and the most suitable equipment must be selected depending on specific site conditions.
The bulldozer is very versatile machine and is used frequently for stripping top soil,
clearing vegetation, pushing scrapers, spreading and grading. The bulldozer can be used
effectively for moving earth over short distances up to 100 m (300 ft ). However many
projects, necessitate a combined load, haul and discharge system at least up to a distance
of 3 km. The situation calls for a robust excavator, capable of travelling over rough
terrain to eliminate the use of trucks and wagons on public roads. The scraper has been
developed specially to cater for this medium distance haul. Essentially the earth is cut and
loaded directly into the scraper box (or bowl), transported to the discharge area and
finally spread in layers. The whole process takes place in a continuous cycle. The type of
machine to be adopted depends upon travelling distance. The loader is a machine which
serves the purpose of both the fixed-position excavator and transporter over short
distances of perhaps 10-20 m (30-60 ft).
3.3.4 Compaction Equipment
Compaction of the backfill within the trench requires special equipment because
of the limited space available between the pipe and the trench wall. Walk-behind
vibratory plate compactor and impact rammers (Fig. 3.6) are the most common and
convenient types of compactors contractors use for compaction of backfill inside a trench
for pipeline installation.
Rammers are the best type of compactor for clay and cohesive soils, where we
need to squeeze out air and excess water. The shoe or foot of rammer will come off the
ground, approximately 2 or 3 inches and then slap down about 600 to 700 times a minute
in order to really pound the soil. The vibratory compactors are well suited for granular
material. However, they do not work well in clay soil because their compacting action
36
tends to pump water to the surfece where it creates mud. The machine bogs down
because it does not have enough amplitude to separate itself from the clay.
The backfill materiiils recommended in the specification other than the flowable
backfill are course granular materials and hence, there should be no problem with using
vibratory plate compactors for compacting backfill ofHDPE pipe installation. Vibratory
compactors and vibratory plates in particular rest du-ectly on the ground. The compactor
with smallest plates dimension measure 12 inches wide by 25 inches long. A rotating
offset weight in the plate creates vibrations. These vibrations reduce the friction between
the soil or gravel particles in backfill, then allow gravity and the weight of the machine to
compact that material. There are two types of vibratory plate compactors: forward-plate
compactors and reversible-plate compactors. Reversing-plate machines are more
productive than forward-plate.
While working in a confined place with a forward plate unit such as inside a
trench, once the pipe is laid workmen have got to turn that machine around, it is hard to
do, because it is designed to go in only one direction only. Forward-plate machines use
one counterbalanced weight to produce compaction energy. A reversing plate machine
uses two. Changing the pitch on one of those weights allows the machine to go from
forward to reverse simply by pulling a lever.
3.3.5 Weight of Equipment
Once the pipe soil envelope is prepared, any of the equipment discussed above
may traverse buried pipe zone and hence affect the structural integrity of the installed
pipe. Therefore, proper cover must be provided to avoid potential damage to the pipe.
The selection of the mmimum cover required, as explained in Section 3.8 is done based
on the operating weight of the equipment. Table 3.5 that provides approximate weight of
most of the construction equipment that might traverse that pipe-soil zone. Data in this
table has been obtained from Caterpillar Performance Handbook, Edition 26.
37
Vibratory Plate Compactor
Impact Rammer
Fig. 3.6: Commonly Used Compactors
38
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3.4 Deficiencies in the Draft Specification
The next step in the constructibility review involved careful examination of each
sub task along with the relevant portions of the draft specification to identify potential
problems in implementation. During this process, the researchers relied heavily upon the
input they collected from the field construction personnel. This review identified a
number of deficiencies or problem areas that deserve special attention. These are as
follows:
a. Minimum trench width requirements,
b. Types of backfill material allowed,
c. Granular backfill gradation specifications,
d. Minimum cover specifications.
Each of these topics is discussed in detail in the following sections.
3.5 Minimum Trench Width Requirements
Section 6.1 of the draft specification deals with trench excavation. It specifies
that "the trench width shall be sufficient, but not greater than necessary, to allow working
room to properly and safely compact haunching and other embedment materials." Since,
in most cases, the native material does not meet the specifications for pipe backfill
suitable material has to be obtained and then transported to the jobsite at a cost.
Therefore, from a project economics standpoint, it is important to keep the trench width
to a minimum. At the same time, however, the trench should be wide enough to allow
placement and proper compaction of the backfill. The minimum trench width
requirements found in the draft specification depend on the type of backfill used. They
are as follows:
Type I Backfill Outside pipe diameter +12 inches.
Type II Backfill Outside pipe diameter x 1.25 + 12inches.
One of the issues that was addressed during this constructibility review involved
the minimum trench width specifications for installations where Type II backfill (i.e.,
granular backfill) was used. The current specification was based on the guidelines found
in ASTM D 2321: Standard Practice for Underground Installation of Thermoplastic Pipe
40
for Sewers and Other Gravity-Flow Applications. However, during the field tests
conducted in this research, it was observed that the above minimum trench width
specifications did not provide adequate room for the operation of backfill compaction
equipment. Therefore, this problem was investigated during the constructibility review.
As a first step, the minimum trench width guidelines developed and used by
various agencies were compiled. These data are shown in Table 3.6. The last column in
this table represents the trench widths calculated by the draft specification. Comparison
of these numbers reveals that there is significant variation in the minimum trench width
recommendations developed by different agencies. For large diameter pipe (i.e., 36in and
above), the AISI Handbook, NCSPA installation brochure and UniBell Handbook
provide the smallest minimum trench widths. Minimum trench widths specified in
AASHTO Bridge Design Manual Sections 12 and 26 are largest. Fig 3.7 shows a
comparison of some of the more commonly used minimum trench width guidelines.
Secondly, the overall dimensions of the more commonly used backfill compactors
were reviewed to determine, the minimum space that would be required to operate these
equipment. Based on the information reviewed it was determined that a minimum of 18
inches will be needed to operate most vibratory plate compactors or impact rammers
without disturbing the pipe. Consequently, the minimum trench widths were calculated
allowing 18in space between the pipe and the trench wall. These calculations are
summarized in Table 3.7. Based on this review, it is recommended that the minimum
trench width in the specification be modified according to Table 3.8. Comparison of the
minimum trench widths recommended in Table 3.8 and those shown in Table 3.6 reveal
that the new guidelines closely match with AASHTO Section 12 and Section 26
guidelines.
41
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44
3.6 Types of Backfill Material
Section 6.8 of the draft specifications deals with backfill materials. It allows the
following two types of backfill materials.
Type I Backfill - Flowable Backfill in accordance with Special Specification
4005.
Type II Backfill - Granular Material that meets the gradation requirements of
Type B, C, D or F aggregate mixtures m Item 334 or Item 340.
One of the key issues addressed during this constructibility review involved the
availability of the specified backfill material at economical prices in various parts of
Texas. To examine this issue, a survey was conducted among the materials or laboratory
engineers in all TxDOT districts. As a first step, a copy of the draft specification was
sent to each district lab engineer. Then they were asked to provide information on the
availability and the cost of each specified backfill material in their district. They were
also asked to identify altemative materials that are economically available within the
region that may be used as HDPE pipe backfill. The information collected from this
survey is summarized in Appendix C. Review of the information received during this
survey lead to the following important findings.
a. Cement stabilized sand is a common backfill material that is widely used by many
TxDOT districts. In some districts, such as Houston and Beaumont this material
is foimd to be more economical than conventional granular backfill. This was
confirmed by data collected during the economic analysis phase of this research.
Therefore, cement stabilized sand should be included in the specifications as an
acceptable backfill material.
b. The mix design of the Special Specification 4005 flowable backfill is designed to
provide a much higher strength than is necessary for pipe backfill purposes. This
flowable backfill is considerably more expensive than other backfill materials. A
TxDOT special task force has examined a number of different flowable backfill
specifications and identified Special Specification 4438: flowable backfill as a
more suitable backfill material for this application. Item 4438 corresponds to a
lower strength (28-day compressive strength of 80-150 psi) and therefore a more
45
economical flowable fill. Therefore, Item 4438 should be used instead of Item
4005 in the specifications for Type I backfill materials. However, concern has
been raised with respect to lack of control on the short-term strength of this
particular flowable fill. Item 4438 specifies the 28-day strength to be a minimum
of 80 psi but does not specify a minimum short-term, say 24 hr, strength. Short-
term strength of the flowable fill is of importance because, in many pipe
installation projects, the trench must be covered up and the highway opened to
traffic as soon as possible. Therefore special attention should be paid to the short-
term strength of the flowable fill when this type of backfill is used in pipe
installation projects.
3.7 Granular Backfill Gradation
Gradation of the Type II granular backfill is specified in Section 6.8 of the draft
specification. In this section it is stated that "Type II backfill consists of granular
material that meets the gradation requirements of Types B, C, D, or F aggregate mixtures
in Item 334: Hot Mix-Cold Laid Asphalt Concrete Pavements and Item 340: Hot Mix
Asphalt Concrete Pavements." Although the specified gradation bands match the HDPE
pipe backfill requirements very well, there is a major difficulty associated with the use of
this specification. In the preparation of an asphalt concrete mix of a specified type,
aggregate of different size fractions are fed into the plant in the correct proportions and
then blended inside the hot mix plant. Accordingly, aggregate blending to achieve
specific gradation requirements of Types B, C, D and F aggregate mixtures is
accomplished within the hot mix plant. Thus, achieving the same Types B, C, D and F
gradations for another application is difficult.
Item 334 and Item 340 were used in the backfill material gradation specification
with the expectation that they will make the task of finding the appropriate material easier
for the contractor. However, experience from the pilot construction projects proved that
it created more ambiguity and confusion for the contractor than it helped him identify
suitable granular backfill. Therefore, the following altemative approach is recommended
for use in the granular backfill specification. Table 3.9 below specifies the gradation
46
band for granular backfill. In addition, items from the current TxDOT Standard
Specification that may meet the specified gradation requirements are identified in a
footnote to the table.
Table 3.9 Gradation Requirements for Type III Backfill
Sieve No.
1 inch /g inch
Vi inch /g inch
No. 4 No. 10 No.200
Percent Retained (Cumulative)
0-5 0-35 0-75 0-95
35-100 50-100 90-100
3.8 Minimum Cover
One of the important aspects that must be addressed in the specification for
installation of the pipe involves the minimum cover requirements to protect the pipe from
vehicular loading. In arriving at a suitable thickness for the minimum cover, one must
consider two types of loadings; (a) loadings from off-road vehicles, such as constmction
vehicles that may traverse the pipe during constmction, (b) repeated loading from
vehicles that travel on the highway once the pipe installation is complete.
In the original version of the specification that was developed by the research
team and presented to the TxDOT project monitoring committee on April 30, 1998,
minimum cover issues were addresses in Sections 3.1 and 4.5.4. Figure 3.8 on the
following page presents the relevant sections from the above specification. During the
constmctibility review, the project monitoring committee (PMC) was asked to review the
specifications and provide their comments. Based on their review, the PMC raised a
question with respect to lack of a clear definition of "heavy constmction vehicles." This
was an important issue because the specification requires the constmction of a special
ramp to provide a minimum 1.2 m (4ft) cover before heavy constmction vehicles could
traverse the pipe. However, building of such a ramp will require the use of constmction
47
vehicles. This raises a question as to which constmction vehicles are not considered
"heavy" and therefore may be used in the constmction of the ramp.
In response to the above comment, the researchers conducted a thorough review
of the existing information on effects of heavy vehicle loading on the thermoplastic pipe
with minimum cover. The findings indicated that, in general, 300mm (1 ft) minimum
cover has generally been found to be adequate to protect the pipe from loading due to
many commonly used constmction equipment such as excavators, rollers, front-end
loaders, backhoes etc. However, larger cover is needed to protect the pipe from
constmction equipment such as earth movers, elevating scrapers and cranes. However,
since each type of constmction vehicle comes in a broad range of models, it is not
possible to categorize constmction vehicles into two classes as "light, for which 300mm
is adequate" and "heavy, for which minimum cover larger than 300mm is required."
Therefore, it is recommended that the specifications be revised in the following manner
as stated in the final specification (Appendix B, pp. 108-109).
The backfill material shall be placed evenly and simultaneously on both sides of the pipe to not less than 300 mm (1 ft) above the top of the pipe. No heavy constmction equipment with axle loads equal to or larger than 40-kips shall be permitted to traverse the pipe trench. If the passage of such heavy constmction equipment over an installed pipeline is necessary during constmction, compacted fill in the form of a ramp shall be constmcted to depth of one pipe diameter above the crown of the pipe.
The recommendations given above are based on information available in
published technical literature. In the third and final year of this research study,
appropriate field testing will be conducted to check the validity of the above specification
for the specific types of backfill material used in TxDOT pipe installation projects.
Revisions, if found to be necessary, will be incorporated in the final version of the
specification that will be delivered to TxDOT at the conclusion of the study.
48
3.1 Minimum Soil Cover
The minimum cover from the pipe crown to the top of the road subgrade or ground surface should be as specified Table 2 below.
Table 2. Minimum Soil Cover Type of Pavement Minimum Cover
inches mm Rigid Pavement Flexible Pavement Unpaved Roadway No Vehicular Loading
12 18 27 21
300 450 675 525
4.5.4 Final Rackfill - Final backfill consists of the zone that extends from 1 ft (300 mm) above the crown of the pipe to the base or final grade. Placement and compaction of the final backfill should be performed according to specifications provided in the plans. Heavy constmction vehicles should not be allowed to cross over the pipe until the compaction has been completed to the finished earthwork grade or to an elevation of at least 4 ft above the crown the pipe. If the passage of constmction equipment over an installed pipeline is necessary during constmction, compacted fill in the form of a ramp shall be constmcted to a minimum elevation of 4 ft (1.2 m) above the crown of the pipe. Any damaged pipe shall be replaced at the contractor's expense.
Fig. 3.8 Excerpts from Draft Specifications that Address Minimum Cover Requirements
49
CHAPTER 4
ECONOMIC ANALYSIS
4.1 Overview
In this chapter, HDPE pipe is compared with reinforced concrete pipe and
cormgated metal pipe in terms of material and installation costs. The chapter begins with
a general economic comparison between different pipe products. This discussion reviews
the advantages and disadvantages of using HDPE pipe in place of concrete and
cormgated metal pipe from an economic point of view. Subsequently, Section 4.2
presents a similar comparison based on data compiled by several other state DOTs on as-
installed costs for different types of pipe. Several interesting observations can be made
from this data analysis and review. First of all, review of data indicates that the
acceptance ofHDPE pipe as a viable altemative has resulted in lower unit bid prices for
all pipe products. Secondly, the available data shows that as-installed costs for HDPE
pipe have been lower than for other pipe products. A detailed review is found in Section
4.2. Section 4.3 presents a comparison on as-installed cost ofHDPE pipe and RCP based
on an analysis performed for some example-pipe-installation projects using a software
named 'PipePac 2000'.
The two main material resources required in large diameter pipe installation are
pipe and trench backfill material. The unit prices for both of these, especially backfill
material, depend largely on the project location. Therefore, the economic analysis
conducted in this study also involved a study of how these parameters vary within the
state. Accordingly, data on backfill material prices were collected from different TxDOT
districts and reviewed. Section 4.3 of this chapter presents the results from the above
data review and analysis.
The last section of this chapter. Section 4.4, presents the findings from a
parametric study. This parametric study is based on a detailed analysis that was
conducted to obtain estimates of as-installed costs for a hypothetical pipe installation
project when pipe installation is performed according to TxDOT specifications. It
examines the influence of pipe material (HDPE vs. RCP), pipe diameter and backfill
material price on overall project cost by varying each parameter within the complete
50
range of values found within Texas. Several useful conclusions were drawn based on the
findings from the above parametric study.
Concrete pipe has thicker pipe wall and is much heavier than its HDPE
counterpart that meets the same stmctural requirements. The heavier weight of concrete
pipe results in higher transportation cost per mile. In other words, a tmck with given
weight carrying capacity can transport a much larger quantity (i.e., total pipe length) of
HDPE pipe than concrete pipe. Because of its light weight and ease of handling, HDPE
pipe can be easily nested and stacked up higher on the tmck allowing a larger quantity of
HDPE pipe to be transported in a single trip. However, it is important to note that this
advantage is somewhat ofi&et by the longer distances that HDPE pipe must be transported
in comparison to conventional RCP pipe. There are fewer number ofHDPE pipe
manufacturing plants when compared with RCP pipe manufacturing plants. For example,
there are only two HDPE pipe manufacturing plants within the entire state of Texas: ADS
pipe manufecturing plant in Enis (near Dallas) and Hancor pipe manufacturing plant in
Yoakum. In comparison, there are more than seven RCP manufacturers within Texas as
listed in Highway Dope Book and& Directory (Whitley & Siddons, Dec. 1998). Some of
those RCP manufacturers have more than one production plants located in different
districts within Texas. Therefore, the average distance from the point of production to
the project site is larger in the case ofHDPE pipe than it is for RCP. A more detailed
discussion of pipe prices can be found later in a subsequent section of this chapter.
In addition to possible savings in transportation costs, the lighter weight of the
HDPE pipe also results in savings in labor cost during installation. Due to the light
weight ofHDPE pipe, less labor is required in its handling and placement. In addition,
because of the lighter weight ofHDPE pipe, they come in longer pipe lengths. The
typical length ofHDPE pipe (also called "stick length") is 20ft whereas the typical length
of RCP is in the range of 8-10ft. Accordingly, HDPE pipe installation involves fewer
joints. This results in significant savings in overall project time and therefore, project
cost. In addition, pipe joints are also the most critical places of the drainage system from
the view point of maintenance. Therefore, it can be anticipated, that fewer joints in
HDPE pipe will lead to lower makitenance costs. The manufacturers of smooth-lined
51
polyethylene pipe (SLPE) also make the claim that SLPE has better hydraulic flow
characteristics than concrete pipe and thus lowering maintenance costs. However,
American Concrete Pipe Association (ACPA) refutes the above claim based on research
conducted by Utah State University (ACPA Concrete Pipe Insights, 1997). ACPA
suggests that an extrapolation of the test values (only 12" through 18" HDPE pipes were
tested) results in laboratory values as high as 0.015 for 24" diameter and 0.019 for 36"
diameter SLPE. These numbers are higher than design Manning's n value of 0.012 and
0.013 that is generally recommended by the concrete pipe industry for RCP. Therefore,
at this point it is not clear whether the smooth lined HDPE pipe does have superior
hydraulic flow characteristics than other pipe products or not.
HDPE pipe, being a more flexible product than reinforced concrete pipe, depends
more on the surrounding backfill material for stmctural support. Therefore, quality
control during the placement and compaction of baickfiU is a very important aspect of
HDPE pipe installation. For this reason, specifications for installation tend to be stricter
for HDPE pipe than those for rigid pipe systems such as RCP. These specifications
typically include requirements for special backfill materials, special precautions during
handling and placement of the pipe, special precautions to avoid potential problems due
to pipe floatation, requirements on larger minimum covers to prevent pipe damage,
requirements to measure pipe deflection to ensure satisfactory installation etc. Such
requirements tend to drive the cost ofHDPE pipe installation higher. Another drawback
that is often cited by highway agencies with regard to the use ofHDPE pipe on a routine
basis is that they are not adequately staffed to provide close supervision that is needed in
such installations. As a result, their HDPE pipe installation specifications tend to be
overly conservative. Unfortunately, when such conservative practices are used, any
economic benefit that could be gained from the use ofHDPE pipe will be lost.
52
4.2 Review of Information from Other States
4.2.1 Introduction
Section 4.1 presented a general comparison between HDPE pipe and reinforced
concrete pipe from an economic point of view. Apart from this general overview, effort
was also made to collect and review data on actual as-installed costs for HDPE pipe from
various agencies that have used this product in highway drainage applications. This
section summarizes the findings from the above review. The review primarily focuses on
two separate issues; (a) the impact of accepting HDPE pipe as a biddable altemative for
large-diameter pipe installations on the unit bid prices for other pipe products, (b)
comparison between the as-installed cost for HDPE versus that for reinforced concrete
pipe. However, as the reader reviews the information presented below, it is important
that he (or she) keeps the following points in mind.
a. The installation costs for a given pipe product depends on the specifications
used in its installation. These specifications may vary significantly from one
agency to another. Stringer requirements will obviously cause the installation
costs to go up. Therefore, the numbers reported for one agency or location may
not apply to another. Additionally local conditions such as availability of
quality granular backfill also play an important role in determining which pipe
product is most economical and what margin of economical benefit it will yield
over other products.
b. This research focuses on large-diameter (36in or larger) pipe category.
Therefore, this economic comparison should strictly be confined to large
diameter pipes only. Unfortunately, the available data did not always categorize
percent savings on installation costs by different pipe diameters. Inevitably,
some loss in accuracy in data analysis occur when data from different pipe
diameters are pooled together.
The authors made every effort to perform an unbiased review. It must be
pointed out that, nearly all of the data that surfaced during their search came from
databases that were compiled by thermoplastic pipe manufacturing industry.
53
Nevertheless, these data were originally obtained from independent agencies such as state
DOTs and City Public Works Departments.
4.2.2 Economic Impact from the Acceptance ofHDPE as a Biddable Altemative
This section deals with the overall impact from introducing HDPE in the bid
process for pipe installation projects for all types of pipe. It includes a review of
available data on actual bid prices for as-installed costs for different pipe products when
HDPE pipe is allowed as a biddable altemative versus when HDPE pipe is not allowed as
a biddable altemative. The above review indicates that the competition created by
including HDPE in the bidding process leads to significant benefit to the transportation
agencies. This benefit is two-fold and is discussed in the following sections.
First of all, the unit bid price for RCP as-installed cost becomes lower when
HDPE is allowed to bid compared to the case where HDPE is not allowed in the bidding
process. Limited data presented in Table 4.1 supports this statement. This table has
been compiled from the South Carolina State DOT Bid Tabulation (Jan 1996 - Feb
1997). Savings on 18in and 24in RCP bid price were found to be 7.6% and 10.4%
respectively as it appears in this table. Unfortunately, similar data was not available for
pipe with larger diameters where bid prices for RCP pipe could be con^ared for the two
bidding environments, i.e., when HDPE was present as a biddable altemative and when
such altemative was not present.
A second and a more significant benefit resulting from the presence ofHDPE in
the bidding process is that it lowers the overall bid price for the as-installed cost for the
pipe installation project.. A con^arative study on available data on average unit bid
prices for installations with different pipe products suggests that unit bid price for HDPE
is the minimum among different pipe products. Therefore, the overall as-installed cost
would be based on HDPE pipe which, according to the data, yielded
54
Table 4.1: Impact on Average Unit Bid Price of RCP when HDPE Pipe was Permitted to Bid as Experienced by SCDOT, 1996-1997
Pipe Diameter
18in
24in
Average Unit Bid Price of As Installed Cost When
RCP is the only Pipe Material ($/ft)
$17.59
$23.7
4
Average RCP Unit Bid Saving on RCP Price of As Installed Cost When HDPE When HDPE was Present was Allowed an
as Altemate ($/ft) Altemate ($/ft)
$16.27
$21.30
7.6%
10.4%
significant savings over RCP as installed cost. Table 4.2 summarizes the available data
on unit bid prices for pipe installations when HDPE was available as a biddable
altemative. Majority of the data shown in Table 4.2 is limited to HDPE and RCP.
However, in some instances, they include bid prices for other pipe products such as CMP
as well. Pipe diameter tabulated in Table 4.2 ranges from 18in through 42in. Only Iowa
State DOT has the experience with bidding and using 42in pipe and no data is available
for 48in diameter pipe. Accordingly, these pipe installations have been completed during
the time period from 1989 through 1999 and all available data have been tabulated in
chronological order. In Table 4.2, it is noticed that as-installed cost for HDPE pipe of
same diameter varied significantly from once state DOT to another. For example, for
36" diameter HDPE pipe as-installed costs were $45.84, $26.38, $39.03 and $42.39 as
experienced by NYSDOT, ODOT, OKDOT and SCDOT, respectively, in the time range
from 1991 through 1997. Ohio DOT's as installed cost is noticeably lower than any other
state DOTs'. The use of different specifications by different agencies and local
conditions such as availability of specified backfill material may explain the observed
cost variation from one state DOT to another. Additionally, all of the reported data do
not correspond to the same time period. This makes direct comparison difficult owing to
rising labor and material costs. Interestingly however, review of data from NYDOT for
which data was available for both 1991-92 and 1998-99, shows that the as-installed cost
55
has remained neariy the same over the 7 year period. In fact, the as-installed cost for
36in diameter pipe has come down. Subsequently, Table 4.3 which presents the same
information in summary form shows the fact that percent savings reported by different
state transportation agencies varied widely. Maximum savings due to low bid price of
HDPE pipe is as high as 61% relative to RCP bid price. The minimum savings relative to
RCP was 16.% for bidding on 30in diameter pipe as experienced by NY State DOT when
HDPE pipe was bid on an equal basis along with RCP and CMP.
Also it is of interest to note that percent savings for comparatively smaller
diameter pipe such as 18in, 24in were similar to those for HDPE pipe of diameter as high
as 30in, 36in and 42in. Thus, the state DOT data reported above lead to the conclusion
that HDPE pipe is more economical than RCP pipe for both smaller diameter and large
diameter pipe. In addition to this comparative review on unit bid price of as-installed
cost ofHDPE and other pipes, the history of using HDPE along with RCP and CMP by
NY State DOT in the past few years support the same view. This data is presented in Fig.
4.1. This figure has been derived from data published in Cormgated Polyethylene Pipe
Association (designated as CPPA) Press Release, dated April 7, 1997. The original
source of these data was NYSDOT Material Bureau. NYSDOT began using large
diameter HDPE pipe in 1989. Fig. 4.1 shows that even though the total use ofHDPE was
just 1% in 1989, the percentage ofHDPE pipe use in the following years gradually
increased. As a continuation of this fact cormgated HDPE pipe accounted for 48 percent
of all large-diameter pipe used in 1996 roadway drainage projects. Fig. 4.1 speaks for
itself and it depicts the fact of increasing popularity ofHDPE in the state projects and the
reason is obviously the savings in installation costs for making HDPE as their material of
choice in place of RCP or CMP.
56
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58
Table 4.3: Percent Savings due to Presence ofHDPE in the Bidding Process
Pipe Diameter
I Sin
24in
30in
36in
42in
48in
Percent Savings (%)
24.0 -52.9
21.0-55.0
16.0-61.0
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No Data Available
4.3 Comparison ofHDPE and RCP As-installed Cost Based on Analysis Performed with TipePac 2000'
In addition to the comparison made in the previous section based on the actual
bid prices, an analysis was performed using Cost Analysis of Pipe Envelope (referred to
as CAPE) of the software PipePac 2000. American Concrete Pipe Association has the
copyright for this software. 'PipePac 2000' allows calculation of as-installed costs for
both RCP and HDPE pipe. Any analysis performed using this software represents
economic perspective of concrete pipe industry about various pipe products.
This section summarizes the results from the analysis performed for several
example-projects ofHDPE and RC pipe-installation in order to get the comparative
picture on which pipe product is economical. The main parameters requiring input for
the analysis are pipe price, pipe diameter, hauling and tippmg rate and granular backfill
price. Trench dimensions such as trench width, bedding depth, excavation height receive
default values once a diameter is selected for an analysis. As-installed cost ofHDPE and
RC pipe estimated using this software is listed in Table 4.4. RCP Installation type Class
C is listed which assumes the use of native soil for backfilling. RCP price considered in
this analysis is the minimum listed pipe price of Hanson Concrete Products. Whereas
HDPE pipe price is typical price for Texas region listed by Advanced Drainage System,
Inc. Savings from using HDPE pipe were calculated accordingly. Table 4.4 shows that
approximately 7% to 9% savings on using HDPE pipe is possible over RCP.
59
It must be noted that there are a number of significant limitations in the PipePac
2000 analysis. The software estimates the total pipe installation cost as the sum of cost
of the pipe, cost of backfill material and cost of removal and disposal of excavated native
soil. It does not consider cost of labor and equipment for the installation. Therefore, it
does not appropriately consider reduction in cost due to less labor and faster installation
ofHDPE pipe resulting from the lighter weight and longer joint spacing for this type of
pipe.
4.4 Economics: State of Texas
4.4.1 Introduction
Data presented and discussed in the preceding section clearly indicate that there is
significant economic incentive for transportation agencies to include HDPE pipe in the
bidding process for pipe installation projects. At the same time, however, it is important
to point out that the pipe installation costs vary with the installation specifications used
by each agency. The pipe installation costs also vary from one location to another
depending on local conditions such as availability of specific types of backfill materials.
Also, the analysis performed with PipePac 2000 does not consider some of the important
factors that affect the total installation cost ofHDPE pipe and RCP. Therefore, before
any conclusions could be reached concerning the potential savings to be gained by
TxDOT from the use ofHDPE pipe, it is necessary to perform a closer review of the
specific conditions that exist within Texas. Consequently, a survey was performed to
determine the pipe prices and backfill material prices within various parts of Texas.
Among all the parameters that influence the overall pipe installation cost, these two, viz.
pipe price and the backfill material price are most liable to vary from one region to
another. The findings are summarized in the following two sections 4.3.2 Pipe Price and
4.3.3 Backfill Material Price. Subsequently, in Section 4.4 this information is used in a
detailed economic analysis to determine cost of pipe installation according to draft
specifications developed in this research.
60
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62
4.4.2 Pipe Price
In order to have the most recent pipe price information in different parts of Texas,
the two largest HDPE pipe manufacturers in Texas and two concrete pipe manufacturers
were contacted. Each of these companies was asked to provide price quotations for their
products. Table 4.5 lists price of smooth interior cormgated HDPE pipe for pipe
diameters ranging from 18in to 48in. The listed prices include the price of pipe, joints
and freight cost. Manufacturer 1 recommend that if delivery is requested earlier than 5
days, extra freight cost will be added. For overnight delivery, an extra $200+$ 1.67 per
mile is required. The prices listed for manufacturer 2 could be considered delivered
prices anywhere within Texas, provided the order was in full tmck load quantities. If the
order was less than tmck load amounts, a freight charge could be applied. This amount
would be no more than $150.
Table 4.5: Typical Smooth Interior Wall Cormgated HDPE Pipe Pricing (May 12, 1999)
Diameter Length Price/ft^$) Price/ff($) Manufacturer 1 Manufacturer 2
18" 24" 30" 36" 42" 48"
20' 20' 20' 20' 19.5' 19.5'
6.30 9.71 15.97 19.43 30.45 36.71
5.95 9.44 16.65 20.00 27.00 34.00
Similariy, prices per ft of ASTM C-76 Class III (Tongue and Groove Joint)
reinforced concrete pipe from the two RCP companies are shown in Tables 4.6, 4.7 and
4.8. Table 4.6 shows the price quotations provided by the first RCP manufacturer in the
vicinity of San Antonio while Table 4.7 shows the RCP pipe prices for Dallas Fort Worth
and vicinity. Table 4.8 are price quotations obtained by a second RCP manufacturer, also
for Dallas Fort Worth metropolitan area and its vicinity. These figures include the price
of the joints.
63
One significant difference that can be observed between the price tabulations for
HDPE pipe and RCP is that RCP prices vary with the distance between the
manufecturing plant and the project location whereas HDPE prices do not. This
difference is due to the significant costs associated with the transportation of RCP. This
is an interesting observation because, in comparison to RCP, the HDPE pipe
manufecturing plants are few and far between. For example, each of the two concrete
pipe suppliers mentioned above, has six RCP manufacturing plants in different parts of
Texas. The HDPE pipe manufacturer, on the other hand, has only one manufacturing
plant in Texas that serves the whole state and some of the neighboring states as well.
Nationwide, they have 33 storage locations and 4000 independent distributors.
Nevertheless, the average distance from the point of production ofHDPE pipe to point of
pipe mstallation is much larger than for RCP pipe. The information presented in Tables
4.6, 4.7 and 4.8 shows that despite longer transportation distance, HDPE pipe price is
lower than concrete pipe. The probable reason for this is the difference in cost of raw
materials used in the production of the two different types of pipe.
It was also reported that price of RCP varies with the quantity ordered. In other
words, contractors receive discounts when they order large quantities. Based on the
information received from RCP manufacturers, these discounts may be as high as 20%.
According to information presented in Table 4.6, the minimum listed price for RCP
corresponds to RCP pipe produced at San Antonio plant and delivered within Zone I.
Accordingly, the least possible price of RCP could be calculated by applying 20%
discount to that minimum RCP price. Figure 4.2 presents a con^arison ofHDPE pipe
price against RCP pipe prices for pipe diameters ranging from 18in to 48m. In this
comparison the HDPE prices from both the manufacturers were used. Because RCP
prices varied from one delivery zone to another, the maximum price, the minimum price
and minimum price with 15% discount are plotted. It shows that HDPE pipe price listed
by each of the two manufacturers is lower than RCP pipe price even when a high
discount rate of 15% is applied.
64
4.4.3 Backfill Material Price
4.4.3.1 Overview
Backfill material is one of the most important among all the factors that control
the as-uistalled cost of the HDPE pipe installation. The new backfill material
specifications have been developed so that satisfactory pipe performance can be ensured
with reasonable level of quality control during backfill placement and compaction.
Most native soils will not meet these specifications and therefore, suitable backfill
materials must be obtained from outside sources and transported to the site. Thus, the
specified backfill material comes at a cost and it is an important element that must be
considered in the estimation of the as-installed cost of the pipe. The availability of a
given type of backfill material and its price vary significantly from one location to
another. Therefore, as part of this economic analysis, information on availability and
price of each type of specified backfill material types within different regions of the state
was collected and reviewed. The findings from the above review is presented in this
section of the report.
Section 4.3.3.2 below begins with a detailed description of the data collection
procedure. It also presents all the data collected in tabular form. Subsequently, it
presents the findings from the data review and analysis. The data review was performed
with the following specific objectives in mind. First of all, the prices of different types of
backfill material allowed in the specifications are reviewed to establish the general price
range for each. Secondly, the price quotations obtained from different regions are
examined to determine whether they show any trends or patterns with respect to
geographical location. Finally, the findmgs from this review are used to detemme the
overall as-installed cost of the pipe with each type backfill material allowed by the
current specifications. These as-installed costs are also compared with as-installed costs
of RCP pipes of same diameter.
65
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68
4.4.3.2 Data Collection
The first step in the review process involved the collection of data on current
backfill material prices in various parts of Texas. This was accomplished in two
different ways:
a. Contacting laboratory engineers in TxDOT districts and collecting their input on
prices of suitable types of backfill materials that are economically available in
each district.
b. Extracting data from TxDOT's website that publishes 12-month average unit bid
prices based on construction projects that have been completed in each district.
Backfill price data obtained from district lab engineers in all 25 TxDOT districts
are listed in Appendix C. Table 4.10 is an excerpt from Appendix C that lists some of the
more economical materials available in various parts of Texas. Similarly, data collected
from average bid price tabulations published in TxDOT's website are summarized in
Tables 4.11, 4.12, and 4.14. They represent the average unit bid prices compiled from
numerous projects during the year, 1999. Table 4.13 shows unit bid prices for cement
stabilized backfill (also referred to as Type II backfill in the specification for thermo
plastic pipe), whereas Table 4.14 summarizes the bid prices for flex base materials.
However, not all the data that were collected in this manner could be directly
used in fiirther analysis. First of all, it could be easily seen that unit bid prices for
backfill material were quite sensitive to the quantity of material supplied. In general, the
unit price decreases as the quantity supplied increases. As a result, unit price applicable
to one project may not be directly compared with unit price for another unless the
quantities of backfill material supplied in the two cases are similar. Another factor that
makes direct comparison of backfill material difficult involves the form in which backfill
prices are reported. For example, in Table 4.14, unit bid prices of flexible base material
are tabulated in two forms: 'roadway delivery' price and 'complete in place' price.
Roadway delivery price refers to the price of flexible base material delivered at the job
site and thus, it includes the cost of transportation of the material. On the other hand,
price of flex base in 'complete in place condition' includes cost of material, cost of
transportation and cost of placing of placing the material and compacfing it to specified
69
density. Additionally, because of the volume reduction associated with compaction of
the material, it will be incorrect to compare the 'roadway delivery" price with 'complete
in place' when these prices are reported in $/CY. An even greater difficulty arises with
unit prices of coarse aggregate material used in bituminous mkes. The prices quoted by
most laboratory engineers represented the price of the bituminous mix that included both
aggregate and asphalt binder. Many times these prices represented the price of the
bituminous mk in 'complete in place' condition. Because of these ambiguities, the
bituminous coarse aggregate prices were not included in any fiirther review or analysis.
Among all the backfill materials prices, flowable fill (i.e.. Backfill Material Type
I in the specifications) were the highest. Table 4.11 shows flowable backfill prices for
several districts of Texas. The unit price of flowable fill varied in the range from $53/CY
to $130/CY. However, it must be noted that although the unit price of flowable fill is
higher than that for any other backfill material type, it does not necessarily mean that
flowable backfill will result in higher as-installed cost. First, the specifications allow the
use of a smaller trench width when flowable fill is used. Therefore, the volume of
flowable fill required in a given installation is less than the volume of any other backfill
material type. Secondly, this type of backfill does not require any compaction thus
allows faster installation. These factors may partly offset the higher cost of backfill
material.
70
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71
Table 4.11 : Overall Average Bid Price of Flowable Fill in Texas Districts in 1999
District
Austin San Antonio Beaumont Wichita Falls Corpus Christie Childress Bryan Pharr Fort Worth
Item Number
4156 4156 4158 4438 4438 4438 4438 4438 4438
Qtiantity
3475 840 381 10 5 157 8 237 47
Overall Unit Bid Price of Flowable BackfiU($/CY)
53.47 55.85 68.85 75.00 100.00 120.00 125.00 127.00 130.00
Review of unit price tabulations found on TxDOT website reveals that cement
stabilized materied, i.e.. Type II Backfill in the specifications, is more widely used in
TxDOT construction projects than flowable backfill. Table 4.12 shows the cement
stabilized backfill prices for 24 TxDOT districts. The last column in the table shows the
weighted average price calculated for each district. Conqjarison of these unit prices show
that the price of cement stabilized backfiJl vary significantly. Most of the data lie in the
range between $26/CY and $87/CY although there are a few data points can be found
outside this range. Secondly, it can be observed that the prices of cement stabilized
backfill show a clear price trend according to different geographical location. Table 4.13
categorizes the cement stabilized backfill price into three different ranges; low (less than
$40/CY), medium (between $40/CY and $70/CY) and high (greater than $70/CY).
Subsequently, based on the weighted average price calculated for each TxDOT distrk t,
they are divided into different price zones. These different price zones are depicted in
Fig. 4.3. It shows that the price of cement stabilized is lower near the gulf coast. The
prices show a general increasing trend as you move away from the gulf coast with some
of the West Texas and northern districts showing the highest prices.
The third type of backfill allowed in the specifications is granular backfill. In
most regions, granular backfill is found to be the most economical option among the
three types of backfill materials specified. Once again, review of granular backfill
72
material prices was performed based on input received from district laboratory engineers
as well as unit bid price tabulation available on TxDOT website. Table 4.10 provides a
summary of information collected from district lab engineers. Review of these data
shows that the unit price of granular backfill range from about $9.50/CY to about
$25.00/CY. The next step involved review of information available on TxDOT unit bid
price tabulations. Although, granular material with gradations similar to those specified
is used in many applications including Hot Mix Asphalt Concrete, Surface Treatment,
Portland Cement Concrete, the unit prices for these items cannot be used in this review
because they do not represent cost of aggregate material alone. The only exception was
Item 247: Flexible Base. Therefore, overall average bid prices for flex base in 'roadway
delivery condition' were obtained for 15 TxDOT districts. They are listed in Table 4.14. •
The typical price range appears to be between $7.00/CY and $25.00/CY. It is
worthwhile noting that unit prices reported for 11 out of 15 districts are less than $15/CY.
At the same time, however, it must be pointed out that not all flexible base materials may
qualify for use as backfill imder the proposed specifications because of higher fines
(minus 200) content. Table 4.14 also hsts overall bid prices of flex base as 'complete in
place' condition for all 25 district which varies in the range of $14.51-$35.51. Data
presented in Table 4.14 indicate that flex base is an economically available backfill
material at an average price in almost every district of Texas. Based on the above review,
$10.00/CY was selected as a typical price for granular backfill at the low end while
$15.00/CY was selected as a representative figure for medium price granular backfill.
Based on the above review, the unit prices listed in Table 4.15 were selected as
representative figures for each backfill material category. These unit prices are
subsequently used in the estimation of as-installed costs ofHDPE pipe. This analysis
presented in Section 4.5 below.
73
Table 4.12: Overall Average Bid Price of Cement Stabilized Backfill in Texas Districts in 1999
District
Abilene (ABL)
Atlanta (ATL)
Austin (AUS)
Beaumont (BMT)
Brownwood (BWD)
Bryan (BRY)
ChHdress (CHS)
Corpus Christie (CRP)
Dallas (DAL)
ElPaso(ELP)
Fort Worth (FTW)
Houston (HOU)
Laredo (LRD)
Lubbock (LBB)
Lufldn(LFK)
Odessa (ODA)
Quantity (CY;
45.26
215.70 1,538.00
248.00
752.56 30213.00
78.20
3,018.00 581.00
583.12
47.12 1293.5
42.00 11.40
861.00
256.00 5,724.00
16.10
31,052.73 51,292.34 5,600.66
77,770.00
1,086.84 537.78
745.90 1786.96
722.50 892.6
842.65 1056.40
Average Bid Price ($/CY)
87.00
95.27 62.74
36.23
40.60 25,56
28.00
66.20 69.45
81.88
85.00 30.10
60.00 60.00 68.28
75.30 84.63
128.00
27.94 27.65 10.75 35.21
58.10 54.34
78.47 63.00
68.56 43.40
67.35 82.43
Weighted Average Bid Price ($/CY)
87.00
66.70
36.23
25.92
28.00
66.71
81.88
32.00
67.80
84.23
128.00
26.12
56.85
67.57
54.65
75.73
74
Table 4.12 (Continued)
District
Paris (PAR)
Pharr (PHR)
San Angelo (SJT)
San Antonio (SAT)
Tyler (TYL)
Waco (WAC)
Wichita Falls (WFS)
Yoakum (YKM)
Quantity (CY;
298.20 718.50
1,935.00 3,767.40
936.26 278.76
1,272.53 234.90 512.00
48.40 100.00
301.00 610.30
51.00
3,412.30 2886.00
Average Bid Price ($/CY)
132.6 87.00
62.54 37.67
36.74 83.33
71.53 67.20 68.00
120.00 141.00
61.34 45.18
79.50
39.73 33.87
Weighted Average Bid Price ($/CY)
109.7
46.00
47.43
70.13
134.00
50.51
79.50
36.65
Table 4.13: Different Price Category of Cement Stabilized Backfill in Different Parts of Texas
Districts
AUS, BMT, BWD, CRP, HOU, YKM
PHR, SJT, WAC, LFK, LRD, ATL, BRY, DAL, LBB, SAT
ABL, AML, CHS, ELP, FTW, ODA, PAR, TYL, WFS
Overall Unit Bid Price of Cement Stabilized BackfiU ($/CY)
Below $40 per CY
Between $40 and $70 per CY
Above $70 per CY
Price Level
Low
Mediu m
High
75
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76
Table 4.14: Overall Average Bid Price of Flex Base
Districts
Abilene (ABL) Amarillo (AMA) Atlanta (ATL) Austin (AUS) Beaumont (BMT) Brownwood (BWD) Bryan (BRY) Childress (CHS) Corpus Christie (CRP) Dallas (DAL) El Paso (ELP) Fort Worth (FTW) Houston (HOU) Laredo (LRD) Lubbock (LBB) Lufldn(LFK) Odessa (ODA) Paris (PAR) Pharr (PHR) San Angelo (SJT) San Antonio (SAT) Tyler (TYL) Waco (WAC) Wichita Falls (WFS) Yoakum (YKM)
1 ^ 1 ^
Overall Average Bid Price ($/CY), Roadway Delivery
-
11.74 -
-
-
15.57' -
19.31 12.41
-
-
24.60 -
13.00' -
7.00 6.27'
-
12.51 7.14
43.47' 7.10' 2.51
28.351 12.82
Overall Average Bid Price ($/CY), Complete in Place
20.53 29.20 16.67 20.64 35.51 16.59 27.88 22.68 31.96
33.30 20.51 24.87 31.04 14.51 23.81 32.24 21.00 26.60 29.96 19.18 17.15 31.23 16.94 25.54 24.7
77
Table 4.15: Suitable Backfill Materials Selected for HDPE Pipe As-installed Cost Estimation
Suitable Backfill Material Price {S/CY)
Flowable Backfill (Type I Backfill as specified in revised specificafion), 70.00 typical price in Texas region, source: Appendix C
Cement Stabilized Backfill (Type II Backfill as specified in revised 32.00 specification), low price zone, source: Table 4.12
Cement Stabilized Backfill (Type II Backfill as specified in revised 60.00 specification), medium price zone, source: Table 4.12
Flex Base, (typical price), source: Table 4.14 18.00
Granular Backfill Conforming Type III Backfill as specified in revised 10.00 specification, source: Table 4.10
Granular Backfill Conforming Type III Backfill as specified in revised 15.00 specification, source: Table 4.10
4.5 As-Installed Costs for HDPE and Concrete Pipe
Section 4.2 of this chapter presented a comparison between as-installed costs of
HDPE pipe versus concrete pipe based on data available from other states. These data
generally indicated that HDPE pipe provides savings of 20-40% over RCP. However,
because of the differences in specifications used by different agencies and availability
and prices of backfill materials, the percent savings reported by other state DOTs do not
necessarily apply to Texas. Yet again. Section 4.3 revealed the fact that savings of 7% -
9% on as-installed cost can be achieved from using HDPE pipe over RCP according to an
analysis performed with 'PipePac 2000' which is a software used by concrete pipe
industry. However, 'PipePac 2000' does not perform an analysis with all the details of
construction processes required for a high quality installation ofHDPE pipe following the
final specification (Appendix B). It does not consider cost of labor which is not same for
installation with light-weight HDPE pipe and heavy-weight RCP. Therefore, an
economic analysis was conducted in this study to estimate the as-installed costs for both
HDPE pipe and RCP. This analysis was performed for a hypothetical pipe installation
project where the pipe diameter, pipe price and backfill material price were varied within
78
typical ranges as established through previous analysis. The findings from this analysis is
presented graphically so that comparisons can be made between installation costs for
HDPE and RCP for a variety of pipe diameter, pipe price, backfill price combinations.
Section 4.5.1 presents details with regard to sources of data used and assumptions made
during analysis
4.5.1 Sources of Data and Assumptions Made for Model Project Analysis
A detailed work breakdown structure for the entire pipe installation process was
developed in Chapter 3 as the part of the constructibility review. This work breakdown
structure is presented in Table 3.2. Table 3.2 lists sub-tasks associated with different
stages of construction as well as resources (i.e., manpower, equipment and materials)
needed for the completion of each sub-task. In this cost analysis the above work
breakdown structure was further expanded to include the costs associated with each
construction activity. This enhanced work break down structure for installation ofHDPE
pipe is given in thesis as Appendix D. This new itemization forms the primary basis for
the economic analysis presented here.
The analysis in this section calculates approximate as-installed cost ofHDPE pipe
and concrete pipe installation of 18 in., 24 in., 30 in., 36 in., 42 in. and 48 in diameter for
identical utility. The whole analysis is done in one MS Excel Spread Sheet which has
been attached as Appendix E. The sources of relevant resource price information for this
analysis are as follows.
a. Information on equipment rental price, equipment capacity, equipment
size, workers wage and installation cost per unit for each sub-task is available
in Table D.l of Appendix D. Appendix D was compiled following
National Construction Estimator edited by Killey and AUyn (1997) and
Means Heavy Construction Cost Data (1998).
b. Backfill material price of six categories has been used from Table 4.15 that was
selected after a thorough review on all available backfill price data presented in
section 4.4.2.
79
c. From Table 4.5, HDPE pipe price of manufecturer l(Advanced Drainage
Systems, Inc.) was used for estimating as-installed cost. Among the prices of
RCP listed in Table 4.6, 4.7 and 4.8, RCP unit prices of the foUowing categories
have been selected to be used in this estimating:
(a) Minimum RCP price. Zone 1 of CSR Hydro-conduit, with 15%
discount
(b) Minimum RCP price. Zone 1 of CSR Hydro-conduit without discount.
(c) Minimum RCP price(FOB), priced by Hanson Concrete Products.
(d) Minimum RCP price, Hanson Concrete Products with 15% discount.
(e) Maximum RCP price, priced by Hanson Concrete Product.
(f) Discounted RCP price of Zone2, CSR Hydro Conduit.
(g) Discounted RCP price of Col. 3, Table 4.8, Hanson Concrete Products,
(h) Discounted RCP price of Col. 4, Table 4.8, Hanson Concrete Products,
(i) Discounted RCP price of Col. 6, Table 4.8, Hanson Concrete Products.
The estimation documented as Appendix E is based on some assumptions. It was
assumed that the route was perfectly flat terrain and the trench depth required was
minimum. This means that the crown of the pipe laid down in the trench remained
exactly at one pipe diameter depth according to the revised recommendation made in
section 3.8 in Chapter 3. The lengths of the pipe lines were adjusted as 170 m, 140 m,
140 m, 240 m, 220 m, 200 m for 18 in., 24 in., 30 in., 36 in., 42 in. and 48 in. diameter
HDPE pipe respectively in order to get project duration as whole number of days. For
the same reason the lengths of the pipe lines were adjusted as 90 m, 90 m, 65 m, 120 m,
110 m, 110 m for 18 in., 24 in., 30 in., 36 in., 42 in. and 48 in. diameter RCP
respectively. The project duration was rounded up in each case. For concrete pipe
excavated native soil was considered for backfilling. For HDPE pipe backfill material of
sk suitable categories presented in Table 4.15 were considered. Nine different concrete
pipe prices, mentioned previously, were used due to the distance of sites from the
manu&cturing plants. For 18 in., 24 in. and 30 in diameter pipe two temping rammers
with 10 in. plate width have been used. And for 36 in., 42 in., and 48 in. diameter pipe
two vibratory plate compactors with 12 in. plate width have been used. Two large
80
capacity backhoes will be rented. Backhoel will be doing the whole excavation job.
Backhoe2 is the larger of the two backhoes and it will perform three tasks: backfilling,
installing trench boxes and laying pipe in the trench. The total busy hrs of Backhoe2 will
determine the project duration and Backhoel will do some other subtasks like putting the
extra excavated material in the hauling truck during its idle time.
Keeping the above scenario in mind MS Excel Spread Sheet was chosen as a
convenient environment to perform this estimation by varying most significant
parameters in all possible ways. The following section performs a graphical comparison
between HDPE and RCP using the findings from the estimates presented in Appendix E
4.5.2 A Comparative Review on Findings of Model Project Estimation for Competing HDPE and RCP
The resource parameter that mainly affects as-installed cost ofHDPE pipe is
backfill material price of varying category which was discussed in Section 4.4.3. On the
other hand, varying RCP price for different supply zones appeared to be the main
resource parameter for estimating as-installed cost of RCP. Estimated as-installed cost of
HDPE pipe and RCP listed in Appendix E is summarized in Table 4.16 for relevant
resource price conditions in the districts of Texas. Prior to comparing HDPE and RCP
as-installed cost, gradients of as-installed cost of RCP with respect to six pipe diameter
categories have been plotted in Fig. 4.4. This plot also gives an idea in what range as-
installed cost of RCP can vary when pipe can be procured to the site at discounted
minimum unit price or pipe needs to be procured from a remote production plant at the
maximum unit price of RCP.
Figures 4.5, 4.6, and 4.7 immediately compares as-installed cost ofHDPE pipe
with as-installed cost of RCP for all the six pipe-diameter category on the basis of
gradually declining level of RCP price. The curves showing as-installed cost of RCP in
Figures 4.5 consider procuring RCP to three different project-site at distances of 70miles,
100 miles and 130 miles away from the manufacturing plant at 15% discount. The
manufacturers usually consider discount on listed prices in case of a large supply or on
the basis of long term business with pipe buyers. Three curves for as-installed cost of
81
HDPE which considered procuring granular backfiU @$10/CY, granular fiU @$15/CY
and Flex Base @$18/CY show clear savings over RCP. Fig. 4.6 compares as-installed
cost ofHDPE with fliat of RCP when RCP was considered to be procured to the site at
minimum pipe price of CSR Hydro Conduit and minimum pipe price at freight on board
condition (subsequently referred to as FOB) priced by Hanson Concrete Products. HDPE
appears to be cheaper again if granular backfill procured to the project-site @$10-
$15/CY. In Fig. 3.7, as-installed cost ofHDPE considering backfill price below $18/CY,
competes with as-installed cost of RCP which considered procuring RCP with discounted
minimum prices.
However, as-installed cost ofHDPE were maximum when cement stabilized
backfill @$60 and Flowable Fill @$85 were used in estimating. It can be inferred that if
the use of flowable backfill or high priced cement stabilized backfill can be substituted by
some kind granular backfill material locally available in the district of project site, HDPE
pipe can be an economically attractive stand in for RCP pipe.
Percent savings from using HDPE pipe as estimated in this analysis have been
listed in Table 4.16. Savings from using HDPE have been considered in comparison to
as-installed cost of RCP price for various RCP pipe price categories. The table speaks for
itself and leads to the fact that HDPE can be a suitable altemative of RCP under certain
resource price and availability conditions. Most of the numerals listed in Table 4.17 as
percent savings from HDPE over RCP lie between 10% and 15%. Maximum savings
appeared in this analysis is approximately 23% and minimum savings is 2.7%. In
general, it can be inferred from this analysis that if the backfill material that meets the
recommendation can be procured at a price lower than $20/CY, HDPE can compete with
RCP.
All the comparisons on resource prices and as-installed cost ofHDPE pipe and
RCP presented in this chapter are based on present-value-cost-data. A life cycle cost
analysis would would provide a more rational basis for cost comparison between HDPE
and RCP. However, data necessary for such analysis is not available because HDPE pipe
product that is currently available in the market has not been in use for many years. The
specification for the resin to be used for manufacturing HDPE pipe also demands change
82
within a short period of time due to its quality iiiq)rovements through research. These are
the reasons why a life cycle cost analysis for HDPE pipe installation was beyond the
scope of this research. Thus a con^arison based on as-installed cost ofHDPE pipe and
RCP in the only viable altemative at this time.
83
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90
CHAPTER 5
CONCLUSIONS
5.1 Introduction
The previous chapters in this thesis examined the use ofHDPE pipe in TxDOT
construction projects from two very important and practical viewpoints. One of these
two viewpoints involved the constructibility of the HDPE pipe system according to
specifications. Constructibility is an important aspect in large diameter HDPE pipe
because of its flexibility and dependence on surrounding backfill for strength to carry
imposed loads. As result, quality control during pipe installation deserve special
attention. This review, which was described in Chapter 3, examined the draft
specification from a constructibility standpoint and hence identified elements in the
specifications that may create difficulties during its field implementation. The final
specification that was developed by incorporating the recommendations from the
constructiblity review is found in this thesis as Appendix B. Another important issue that
affects the successful implementation of the new HDPE pipe specifications is economics.
Prior to using HDPE pipe in TxDOT projects, it was necessary to verify that that the
installation ofHDPE pipe according to new specifications is economically viable.
Therefore, in Chapter 4 of this thesis, necessary economic analyses were performed to
compare cost ofHDPE pipe installation with those of other traditional pipe products such
as RCP. As a part of tfiis analysis, bid prices for installation of HDPE, RCP and CMP
from highway agencies in other states were reviewed. A second comparison was
performed based on results from a sofhvare named 'PipePac 2000.' Subsequently, the
prices of two of the most important resources for pipe installation projects, i.e., pipe price
and backfill price were in various parts of Texas were compared. Finally, the above data
on pipe price and backfill price were incorporated into a more detailed analysis in which
as-installed costs ofHDPE and RCP were estimated and compared. Consequently, the
findings of that estimating were presented graphically in the concluding section of
Chapter 4. The findings showed that, in certain resource availability conditions, HDPE
pipe can provide significant economic benefit. The following sections document the final
91
conclusions and recommendations from the constructibility review and economic
analysis.
5.2 Conclusions
5.2.1 Conclusions: Constructibilitv Review
The constructibility review identified a number of deficiencies or problem areas
in that draft specification that required special attention. Revisions to overcome these
deficiencies were incorporated into a final specification dated August, 1999. These
revisions are summarized below:
a. Cement Stabilized Backfill is added as a third type of backfill that is acceptable
for use in HDPE pipe installations. In the final specifications this type of backfill
is identified as Type II backfill.. This revisions was based on the finding that
cement stabilized backfill is economically available and widely used in parts of
Texas, specially in TxDOT districts near the Gulf coast.
b. For Type II and III backfill materials that require compaction, wider minimum
trench widths are recommended to ensure there is adequate room to operate
commonly used compaction equipment. Recommended minimum trench widths
for HDPE pipes of 18", 24", 30", 36", 42" and 48" are listed in the final
specification.
c. A suitable gradation band for granular backfill materials was developed. This
gradation band is used in the new specifications in lieu of the previous backfill
material specifications that relied on Spec. Items 334 and 340 to define
gradation for granular backfill. The new gradation requirements are presented in
the final specification in a separate table. All the granular backfill materials that
fit in that gradation band are now referred to as Type III backfill,
d. The minimum backfill cover above the pipe crown is recommended to be revised
in the following manner as stated in the final specification (Appendix B, pp. 108-
109).
92
The backfill material shall be placed evenly and simultaneously on both sides of the pipe to not less than 300 mm (I ft) above the top of the pipe. No heavy construction equipment with axle loads equal to or larger than 40-kips shall be permitted to traverse the pipe trench. If the passage of such heavy construction equipment over an installed pipeline is necessary during construction, compacted fill in the form of a ramp shall be constructed to depth of one pipe diameter above the crown of the pipe.
5.2.2 Conclusions: Economic Analysis
The comparative economic analysis performed in Chapter 4 examined the
economic competitiveness ofHDPE pipe against the most widely accepted and used pipe
product, RCP. This analysis was based on all the present costs involved in initial
installation of the pipe system.. A more appropriate comparison between these two pipe
products would bebased on life cycle costs. Such an analysis, however, is not possible
because there is no adequate data on the performance and service life of the HDPE pipe
products that are currently available in the market. Therefore, it is beyond researchers
scope to observe or predict its performance of these pipe products in the future. As a
result, the conclusions made in this section is based on initial costs of pipe installation.
The findings from economic analysis can be summarized as follows.
a. As-installed bid prices ofHDPE and RCP in the projects undertaken by many
transportation agencies led to the important conclusion that allowing HDPE as a
biddable altemate along with RCP may result in significant savings.
b. Two most important resources that affect the overall project cost are pipe price
and backfill price. Data collected on pipe prices shows that HDPE pipe is
cheaper compared to RCP even though the number ofHDPE production plants
are fewer compared to that ofRCP manufacturing plants and the hauling
distances are longer. Also, HDPE pipe price does not vary for different supply
zone in Texas whereas RCP pipe price does vary with distance to supply zone.
However, HDPE pipe does require special kind of backfill material which often
has be obtained and transported to the project site at a cost.
c. A survey on availability of different backfill materials was performed prior to
93
estimating as-installed cost ofHDPE pipe and RCP required. It was found that
the price and availability of cement stabilized backfill shows a geographic
pattem in Texas districts. It is a readily and economically available backfill
material in the TxDOT districts along the gulf coast. The fiirther a district is
from the coast the higher its price is. Flowable fill appears to be most expensive
of all backfill materials. Flex Base and other granular backfill were found to be
a commonly available backfill material at comparatively low price.
In general, estimated as-installed costs ofHDPE was found to be cheaper than
as-installedcost ofRCP when flex base @ $18/CY, granular fill @$10/CY and
granular fill @$15/CY were used.. In this comparison, as-installed cost ofRCP
was estimated for the following cases: (i) When RCP is procured at minimum
price (freight on board), (ii) discounted minimum price and (iii) discounted
price applicable for a site 30-130 miles away from plant. Savings from using
HDPE pipe as estimated in the analysis were presented in Table 4.17 of Chapter
4. Most of the numbers listed in Table 4.17 as percent savings from HDPE over
RCP lie between 10% and 15%. Maximum savings obtained from this analysis
is approximately 23% and minimum savings is 2.7%. In general, it can be
inferred that if the backfill material that meets the recommendation can be
procured at a price lower than $20/CY, HDPE will be more economical than
RCP.
d. Even though the unit price of Flowable backfill is the highest of all ($85/CY) it
did not result in the maximum as-installed cost. This is due to the fact that
minimum trench width requirements for flowable backfill is smaller and
installation is faster. The cement stabilized backfill at $60/CY resulted in the
maximum as-installed cost.
5.3 Recommendations
Overall, this thesis has presented reviews of critical problems that might arise
during real world implementation of the specification developed for installation ofHDPE
pipe from two viewpoints: construction and economy. This research explored how
94
construction processes determine minimum dimensional requirements of trenches to be
excavated. The research on economic aspects ofHDPE pipe installation shows that
FIDPE can be competitive with other, traditional pipes in the larger diameter category
under many resource availability conditions. Based on the constructibility review and
economic analysis performed, the following final recommendations are made:
a. Based on analysis of actual as-installed cost data of statewide HDPE and RCP
pipe installation projects and estimated as-installed cost of several
hypothetical projects, it is recommended that HDPE should be accepted as a
biddable altemative.
b. The economic analysis was performed based on present value cost data of all
the resources. In future work, a life cycle cost analysis can be performed
which would consider the appropriate depreciation value ofHDPE pipe over a
period of time.
c. Developing an online 'Lessons Leamed Database' on constmction processes
and most recent price/availability picture of various resources is
recommended.
95
LIST OF REFERENCES
AASHTO, (1992). Standard Specification for Highwav Bridges. Edition 15, Section 18, "Soil-Thermoplasfic Pipe Interaction System," pp. 321-326.
Anderson, Stuart D., and Fisher, Deborah J. Constmctibility Review Process for Transtx)rtation Facilities Workbook. NCHRP Report 391, National Academy Press, Washington, D.C., 1997.
ASTM, D2321 (1993). "Standard Practice for Underground Installation of Thermoplasfic Pipe for Sewers and Other Gravity-flow Applicafions," ASTM Book of Standard. pp. 116-124.
Braden, Clay. RCP Price List, CSR Hydro Conduit, San Antonio, Texas, May 13, 1998.
Caterpillar Performance Handbook. Edition 26, CAT Publication by Caterpillar Inc., Peoria, Illinois, USA, October 1995.
Ellis, Tom. HDPE Pipe Price List, Quail Piping Products, Inc., Mangola, Arkansas, March 2000.
Freieich, David. HDPE Pipe Product Information, Hancors, Inc., Austin, Texas, 1998.
Gambatese, John A., and McManus, James F. "Constmctibility: A Quality Improvement Approach to Transportation Projects," Transportation Research Record 1575. Department of Civil Engineering, University of Washington, Seattle, Washington, D.C.,pp. 116-120.
Goddard, James B. Advanced Drainage Systems, Inc., Drainage Pipe: "The Sense and Dollars of Competition," Paper Presented at the 57th Annual Conference of N.Y.S.A.T.E., May 1997.
Haris, Frank. Modem Constmction and Ground Engineering Equipments and Methods. Second Edition, Longman Group Limited, UK, 1994.
Hunemuller, Brad. HDPE Pipe Price List, Advanced Drainage Systems, Inc., Round Rock, Texas, May 12,1999.
Jasek, Maria. Change Order Review, Yoakum District Office, Constmction Section, April 2000.
Killey, Martin D., and Allyn, Marques. National Constmction Estimator. 45th Edition, Craftsman Book Company, Carlsbad, California, 1997.
96
Kraemer, S., Ginley, D., and Joyce, C. The Life Cycle Analysis of Materials Competition for Pipe in the Constmction Industry. Bureau of Mines Information Circular No. 9279, United States De partment of the Interior.
Means Heavy Constmction Cost Data. Edition 13, R. S. Means, Kingston, Massachusetts, November 1998.
OSHA Regulations and Guidelines: A Guide for Health Care Provider, Standards - 29 CFR, Part 1926 Subpart P - Excavation, Thomson Learning, Florence, Kentucky, 2000.
Pmden, Dale. RCP Price List, Hanson Concrete Products, Inc., Dallas, Texas, May 13, 1999.
U. S. Army Corps. Of Engineers: "Biddability, Constmctibility, Operability, and Environmental Review," Regulation No. ER 415-1-11, Department of Army, Washington, D. C , September 1,1994.
Williams, Debbie. Change Order Review, Constmction Records, Laredo, April 2000.
Wilson, Robert, Chairman, Specification Committee: Statewide Special Specification 4269 (1993) and 4004 (1995), "Thermoplastic Pipe," Special Provision and/or Special Change Memorandum Dated March 15, 1996.
97
APPENDIX A
DRAFT SPECIFICATION FOR INSTALLATION OF
LARGE-DIAMETER HDPE DRAINGE
PIPE DATED MAY, 1998
98
DRAFT SPECIFICATIONS
HIGH DENSFFY POLYETHYLENE (HDPE) PIPE FOR GRAVFTY FLOW DRAINAGE APPLICATIONS
1. Description. This specification shall govern for the furnishing and installing of all 18 in (450 mm) to 48 in (1200mm)' high density polyethylene (HDPE) pipe used in the constmction of thermoplastic pipe culverts, sewer mains, laterals, stubs and inlet leads. The pipes shall be of the sizes, types, design and dimensions shown on the plans and shall include all connections and joints to new or existing pipes, sewer, manholes, inlets, headwalls and other appurtenances as may be required to complete the work.
2. Materials. Unless otherwise specified on the plans or herein, the HDPE pipes and fittings used for gravity flow drainage applications shall conform to the following specifications.
2.1 High density polyethylene pipes and fittings shall meet the requirements as in AASHTO M 294M-96 (for pipes up to 36 inches/900mm in diameter) and AASHTO MP6-95 (for pipes of 42 inches/1050mm and 48 inches/1200 mm in diameter).
2.2 Raw Materials - The pipes and the fittings shall be manufactured from virgin PE compounds which conform to the requirements of cell class 335420C^ as defined and described in ASTM D 3350, except that carbon black content shall not exceed 5 percent.
2.3 Designation of Type - The HDPE pipes used for gravity flow drainage applications shall be of Type S (outer cormgated wall with smooth inner liner) or Type D (inner and outer smooth walls braced circumferencially or spirally with projections or ribs).
2.4 Section Properties - Minimum wall thickness of the inner walls of Type S pipe and inner and outer walls of Type D pipe shall be as specified in Section 7.2.2 of the AASHTO M 294M-96 and MP6-95 respectively. The pipe stiffiiess at 5% deflection, when determined in accordance with ASTM designation D 2412, shall be as specified in Section 7.4 of AASHTO M 294M-96 and AASHTO MP6-95.
The manufacturer shall perform appropriate test procedures on representative samples of each type of pipe furnished, and hence verify that the pipe complies with the specifications. A certificate of compliance shall be prepared and submitted to the Department for review and approval. It shall include the following information: manufacturing plant, date of manufacture, pipe unit mass, material distribution, pipe dimensions, water inlet area, pipe stiffhess, pipe flattening, brittleness, environmental stress crack resistance, and workmanship.
' Nominal pipe size is the nominal inside diameter of the pipe ^ This new cell classification (i.e. 335420C) which is required in AASHTO Section 18 is a higher classification than that found in AASHTO M 294M-96 (i.e. 324420C).
99
3. Inspection. The quality of the materials, the process of manufacture, and the finished pipe shall be subject to inspection and approval by the Engineer at the manufacturing plant. In addition, the fmished pipe shall be subject to fiirther inspection by the Engineer at the project site prior to and during installation.
4. Marking. All pipe shall be clearly marked at intervals of not more than 12 ft (3.5 m), and fittings and couplings shall be clearly marked as follows:
4.1 Manufacturer's name or trade mark 4.2 Nominal size 4.3 Specification designation (e.g. M 294M-96) 4.4 Plant designation code 4.5 Date of manufacture
5. Joints. Joints shall be installed such that the connecfion of pipe sections will form a continuous line free from irregularities in the flow line. Joints shall meet the soiltightness definition in accordance with AASHTO Section 26.4.2.4. Suitable joints are the following:
5.1 Integral Bell-N-Spigot - The bell shall overlap a minimum of two cormgations of the spigot end when fully engaged. The spigot end shall have an O-Ring gasket that meets ASTM F 477: Specifications for Elastomeric Seals (Gaskets) for Joining Plastic Pipe.
5.2 Exterior Bell-N-Spigot_ - The bell shall be fully welded to the exterior of the pipe and overlap the spigot end so that flow lines and ends match when fully engaged. The spigot end shall have an O-Ring gasket that meets ASTM F 477: Specifications for Elastomeric Seals (Gaskets) for Joining Plastic Pipe.
6. Construction Methods. The location of private driveway and side road pipe shall be constructed at locations shown on the plans or as directed by the Engineer.
6.1 Excavation - All excavation shall be in accordance with the requirements of Item 400, "Excavation and Backfill for Stmctures."
The width of the trench for pipe installation shall be sufficient, but no greater than necessary, to ensure working room to properly and safely place and compact haunching and other embedment materials. The space between the pipe and trench wall must be wider than the compaction equipment used in the pipe zone.
When Type I backfill {See section 6.8 below) is used, the minimum trench width is the pipe outside diameter plus 12 inches (300 mm).
When Type n backfill {See section 6.8 below) is used, the minimum trench width is the pipe outside diameter times 1.25 plus 12 inches (300 mm). The contractor can use any trench width above the pipe zone.
6.2 Installation in Embankment - If any portion of the pipe projects above the existing ground level, an embankment shall be constmcted as shown in the plans or as directed by the Engineer for a distance outside each side of the pipe location of not less than five times the diameter and to a minimum elevation of 2 ft (0.6 m)
100
above the top of the pipe. The trench shall then be excavated to a width as specified in section 6.1 above.
6.3 Shaping and Bedding - The pipe shall be bedded in a foundation of compacted granular material that meets the gradation requirements of Type B, C, D or F aggregate mixtures in Item 334, "Hot Mix-Cold Laid Asphalt Concrete Pavements" and Item 340, "Hot Mix Asphalt Concrete Pavements." This material shall extend a minimum of 6 inches (150 mm) below the outermost cormgations or ribs and shall be carefully and accurately shaped to fit the lowest part of the pipe exterior for at least ten percent (10%) of the overall height. When requested by the Engineer, the Contractor shall furnish a template for each size and shape of the pipe to be placed for use in checking the shaping and bedding. The template shall consist of a thin plate or board cut to match the lower half of the cross section of the pipe.
6.4 Handling and Storage - Handling and Storage of HDPE pipe shall be in accordance with the pipe manufacturer's instmctions. Proper facilities shall be provided for hoisting and lowering the pipe into the trench without damaging the pipe or disturbing the bedding or the walls of the trench.
6.5 Laying Pipe — Unless otherwise authorized by the Engineer, the laying of pipe on the bedding shall be started at the outlet (or downstream) end and shall proceed toward the inlet (or upstream) end with separate sections firmly joined together. The pipe should be laid in conformity with the established line and grade and shall have a full, firm and even bearing at each joint and along the entire length of the pipe. The pipe should not rest on the bells at the end and therefore it may become necessary to excavate for the pipe bells. Any pipe which is not in alignment or which shows any undue settlement after laying shall be removed and relaid at the Contractor's expense.
Multiple installation of HDPE pipe shall be laid with the centerlines of individual barrels parallel. Unless otherwise indicated on the plans, the minimum clear distance between the outer surfaces of adjacent pipes shall be equal to 24 inches (600 mm).
6.6 Reuse of Existing Appurtenances - When exiting appurtenances are specified on the plans for reuse, the portion to be reused shall be severed from the existing culvert and moved to new position previously prepared, by approved methods.
Connections shall conform to the requirements for joining sections of pipes as indicated herein or as shown on the plans. Any headwalls and any aprons or pipe attached to the headwall that are damaged during moving operations shall be restored to their original condition at the Contractor's expense. The Contractor, if he so desires, may remove and dispose of the existing headwalls and aprons and constmct new headwalls at his own expense, in accordance with the pertinent specifications and design indicated on the plans or as furnished by the Engineer.
6.7 Sewer Connections and Stub Ends - Connections of pipe sewer to existing sewers or sewer appurtenance shall be as shown on the plans or as directed by the
Engineer. The bottom of the existing stmcture shall be mortared or concreted if necessary, to eliminate any drainage pockets created by the new connection. Where the sewer is connected into existing stmctures which are to remain in service, any damage to the existing stmcture resulting from making the connection shall be restored by the Contractor to the satisfaction of the Engineer. Stub ends, for connections to future work not shown on the plans, shall be sealed by installing watertight plugs into the free end of the pipe.
6.8 Backfilling - Backfill from the pipe bedding up to 1 ft (300 mm) above the top of the pipe is critical for the successfiil performance of the pipe. It provides necessary stmctural support to the pipe and controls pipe deflection. Therefore, special care should be taken in the placement and compaction of the backfill material. Special emphasis should be placed upon the need for obtaining uniform backfill material and uniform compacted density throughout the length of the pipe so that unequal pressure will be avoided. Extreme care should be taken to insure proper backfill under the pipe in the haunch zone.
Backfill material shall meet the following specifications.
Type I - Backfill consists of Special Specification Item 4005, "Flowable Backfill." The flowable backfill shall be placed across the entire width of the trench and shall maintain a minimum depth of 1ft (300 mm) above the pipe. A minimum of 24 hours shall elapse prior to backfilling the remaining portion of the trench with other backfill material in accordance with Item 400, "Excavation and Backfill for Stmctures."
Type n - Backfill consists of granular material that meets the gradation requirements of Type B, C, D or F aggregate mixtures in Item 334, "Hot Mix-Cold Laid Asphalt Concrete Pavements" and Item 340, "Hot Mix Asphalt Concrete Pavements." The backfill material shall be placed evenly and simultaneously on both sides of the pipe to not less than 1 ft (300 mm) above the top of the pipe. The backfill shall be placed in uniform layers not exceeding 8 inches (200mm) of thickness (loose measurement), wetted if required, and thoroughly compacted between the pipe and the side of the trench. Until a minimum cover of 1 ft (300 mm) is obtained, only hand operated tamping equipment will be allowed within vertical planes 2 ft (600 mm) beyond the horizontal projection of the outside surfaces of the pipe.
In the selection of appropriate backfill material, consideration should also be given to possible migration of fines from adjacent native soil materials into the backfill. Where potential for such migration exists, separation geotextiles that meet the requirements of ASSHTO M 288 Section 7 shall be installed between the native soil and the backfill.
6.9 Protection of Pipe - No heavy constmction equipment, such as earth hauling equipment shall be permitted to traverse the pipe trench until a minimum depth of cover above the pipe has been established. Unless otherwise specified on the
107
plans, the minimum depth of cover shall consist of fill compacted to a depth of at least one pipe diameter above the pipe.
Prior to adding each new layer of loose backfill material, until a minimum of I ft (300 nun) of cover is obtained, an inspection will be made of the inside periphery of the stmcture for local or unequal deformation caused by improper constmction methods. Evidence of such will be reason for such corrective measures as directed by the Engineer.
Pipe damaged by the Contractor shall be removed and replaced at no additional cost to the State.
7. _Measurement This item will be measured by the linear foot (meter). Such measurements will be made between the ends of the barrel along its flow line, exclusive of safety end treatments. Safety end treatments shall be measured in accordance with item 467, "Safety End Treatment". Where spurs, branches or connections to existing pipe lines are involved, measurement of the spur or new connecting pipe will be made from the intersection of its flow line with the outside surface of the pipe into which it connects. Where inlets, headwalls, catch basins, manholes, junction chambers, or other stmctures are included in lines of pipe, that length of pipe tying into the stmcture wall will be included for measurement but no other portion of the stmcture length or width will be so included.
For multiple pipes, the measured length will be the sum of the lengths of the barrels, measured as prescribed above.
This is a plans quantity measurement Item and the quantity to be paid for will be that quantity shown in the proposal and on the "Estimate and Quantity" sheet of the contract plans, except as modified by Article 9.8. If no adjustment of quantities is required additional measurements or calculations will not be required.
Flowable backfill will not be measured, but considered subsidiary to this item.
9. Payment The work performed and materials furnished in accordance with this Item and measured as provided under "Measurement" will be paid for at the unit price bid for "HDPE Pipe (Type I backfill)" of the type (if required) and size specified or "HDPE Pipe (Type I or EI backfill)" of the type (if required) and size specified. This price shall be the full compensation for furnishing, hauling, placing and joining of pipes; for all connections to new or existing stmctures; for moving and reusing headwalls where required, for removing and disposing of portions of existing stmctures as required; for the bedding and Type I or EI backfill material as required, for cutting of pipe ends on skew; and for all labor, tools, equipment and incidentals required to complete the work.
Excavation and backfill above the Type I or n backfill will be paid for in accordance with Item 400, " Excavation and Backfill for Stmctures". Safety end treatment will be paid for in accordance with Item 467, "Safety End Treatment".
103
APPENDIX B
FINAL SPECIFICATION FOR INSTALLATION OF
LARGE-DIAMETER HDPE DRAINGE
PIPE DATED AUGUST, 1999
104
DRAFT SPECIFICATIONS (Revised August 16, 1999)
HIGH DENSFTY POLYETHYLENE (HDPE) PIPE FOR GRAVrTY FLOW DRAINAGE APPLICATIONS
1. Description. This specification shall govern for the furnishing and installing of all 18 in (450 mm) to 48 in (1200mm)^ high density polyethylene (HDPE) pipe used in the constmction of thermoplastic pipe culverts, sewer mains, laterals, stubs and inlet leads. The pipes shall be of the sizes, types, design and dimensions shown on the plans and shall include all connections and joints to new or existing pipes, sewer, manholes, inlets, headwalls and other appurtenances as may be required to complete the work.
5. Materials. Unless otherwise specified on the plans or herein, the HDPE pipes and fittings used for gravity flow drainage applications shall conform to the following specifications.
5.1 High density polyethylene pipes and fittings shall meet the requirements as in AASHTO M 294-98 (for pipes up to 48 inches/1200mm in diameter).
5.2 Raw Materials - The pipes and the fittings shall be manufactured from virgin PE compounds which conform to the requirements of cell class 335420C as defined and described in ASTM D 3350, except that carbon black content shall not exceed 5 percent.
5.3 Designation of Type — The HDPE pipes used for gravity flow drainage applications shall be of Type S (outer cormgated wall with smooth inner liner) or Type D (inner and outer smooth walls braced circumferencially or spirally with projections or ribs).
2.4 Section Properties - Minimum wall thickness of the inner walls of Type S pipe and inner and outer walls of Type D pipe shall be as specified in Section 7.2.2 of the AASHTO M 294-98. The pipe stiffiiess at 5% deflection, when determined in accordance with ASTM designation D 2412, shall be as specified in Section 7.4 ofAASHTOM 294-98.
The manufacturer shall perform appropriate test procedures on representative samples of each type of pipe furnished, and hence verify that the pipe complies with the specifications. A certificate of compliance shall be prepared and submitted to the Department for review and approval. It shall include the following information: manufacturing plant, date of manufacture, pipe unit mass, material distribution, pipe dimensions, water inlet area, pipe stiffiiess, pipe flattening, brittleness, environmental stress crack resistance, and workmanship.
6. Inspection. The quality of the materials, the process of manufacture, and the finished pipe shall be subject to inspection and approval by the Engineer at the manufacturing plant. In addition, the finished pipe shall be subject to further inspection by the Engineer at the project site prior to and during installation.
Nominal pipe size is the nominal inside diameter of the pipe
7. Marking. All pipe shall be clearly marked at intervals of not more than 12 ft (3.5 m), and fittings and couplings shall be clearly marked as follows:
7.1 Manufacturer's name or trade mark 7.2 Nominal size 7.3 Specification designation (e.g. M 294-98) 7.4 Plant designation code 7.5 Date of manufacture
5. Joints. Joints shall be installed such that the connection of pipe sections will form a continuous line free from irregularities in the flow line. Joints shall meet the soiltightness definition in accordance with AASHTO Section 26.4.2.4. Suitable joints are the following:
5.1 Integral Bell-N-Spigot - The bell shall overlap a minimum of two cormgations of the spigot end when fully engaged. The spigot end shall have an O-Ring gasket that meets ASTM F 477: Specifications for Elastomeric Seals (Gaskets) for Joining Plastic Pipe.
5.2 Exterior Bell-N-Spigot - The bell shall be fully welded to the exterior of the pipe and overlap the spigot end so that flow lines and ends match when fully engaged. The spigot end shall have an O-Ring gasket that meets ASTM F 477: Specifications for Elastomeric Seals (Gaskets) for Joining Plastic Pipe.
6. Construction Methods. The location of private driveway and side road pipe shall be constmcted at locations shown on the plans or as directed by the Engineer.
6.9 Excavation - All excavation shall be in accordance with the requirements of Item 400, "Excavation and Backfill for Stmctures."
The width of the trench for pipe installation shall be sufficient, but no greater than necessary, to ensure working room to properly and safely place and compact haimching and other embedment materials. The space between the pipe and trench wall must be wider than the compaction equipment used in the pipe zone.
When Type I backfill {See section 6.8 below) is used, the minimum trench width is the pipe outside diameter plus 12 inches (300 mm).
When Type n or Type in backfill {See section 6.8 below) is used, the minimum trench width shall be as specified in Table 1. The contractor can use any trench width above the pipe zone.
6.10 Installation in Embankment - If any portion of the pipe projects above the existing ground level, an embankment shall be constmcted as shown in the plans or as directed by the Engineer for a distance outside each side of the pipe location of not less than five times the diameter and to a minimum elevation of 2 ft (0.6 m) above the top of the pipe. The trench shall then be excavated to a width as specified in section 6.1 above.
106
6.11 Shaping and Bedding - The pipe shall be bedded in a foundation of compacted granular material that is free of organic matter, clay lumps, and other deleterious matter. Such bedding material shall meet the gradation requirements shown in Table 2. This material shall extend a minimum of 6 inches (150 mm) below the outermost cormgations or ribs and shall be carefully and accurately shaped to fit the lowest part of the pipe exterior for at least ten percent (10%) of the overall height. When requested by the Engineer, the Contractor shall furnish a template for each size and shape of the pipe to be placed for use in checking the shaping and bedding. The template shall consist of a thin plate or board cut to match the lower half of the cross section of the pipe.
6.12 Handling and Storage - Handling and Storage of HDPE pipe shall be in accordance with the pipe manufacturer's instmctions. Proper facilities shall be provided for hoisting and lowering the pipe into the trench without damaging the pipe or disturbing the bedding or the walls of the trench.
6.13 Laying Pipe - Unless otherwise authorized by the Engineer, the laying of pipe on the bedding shall be started at the outlet (or downstream) end and shall proceed toward the inlet (or upstream) end with separate sections firmly joined together. The pipe should be laid in conformity with the established line and grade and shall have a full, firm and even bearing at each joint and along the entire length of the pipe. The pipe should not rest on the bells at the end and therefore it may become necessary to excavate for the pipe bells. Any pipe which is not in alignment or which shows any undue settlement after laying shall be removed and relaid at the Contractor's expense.
Multiple installation ofHDPE pipe shall be laid with the centerlines of individual barrels parallel. Unless otherwise indicated on the plans, the minimum clear distance between the outer surfaces of adjacent pipes shall be equal to 24 inches (600 mm).
6.14 Reuse of Existing Appurtenances - When exiting appurtenances are specified on the plans for reuse, the portion to be reused shall be severed from the existing culvert and moved to new position previously prepared, by approved methods.
Connections shall conform to the requirements for joining sections of pipes as indicated herein or as shown on the plans. Any headwalls and any aprons or pipe attached to the headwall that are damaged during moving operations shall be restored to their original condition at the Contractor's expense. The Contractor, if he so desires, may remove and dispose of the existing headwalls and aprons and constmct new headwalls at his own expense, in accordance with the pertinent specifications and design indicated on the plans or as furnished by the Engineer.
6.1 SSewer Connections and Stub Ends - Connections of pipe sewer to existing sewers or sewer appurtenance shall be as shown on the plans or as directed by the Engineer. The bottom of the existing stmcture shall be mortared or concreted if necessary, to eliminate any drainage pockets created by the new connection.
\C\1
Where the sewer is connected into existing stmctures which are to remain in service, any damage to the existing stmcture resulting from making the connection shall be restored by the Contractor to the satisfaction of the Engineer. Stub ends, for connections to future work not shown on the plans, shall be sealed by installing watertight plugs into the free end of the pipe.
6.\6Backfilling - Backfill from the pipe bedding up to 1 ft (300 mm) above the top of the pipe is critical for the successful performance of the pipe. It provides necessary stmctural support to the pipe and controls pipe deflection. Therefore, special care should be taken in the placement and compaction of the backfill material. Special emphasis should be placed upon the need for obtaining uniform backfill material and uniform compacted density throughout the length of the pipe so that unequal pressure will be avoided. Extreme care should be taken to insure proper backfill under the pipe in the haunch zone.
Backfill material shall meet the following specifications.
Type I - Backfill consists of Special Specification Item 4438, "Flowable Backfill." The flowable backfill shall be placed across the entire width of the trench and shall maintain a minimum depth of 1ft (300 mm) above the pipe. A minimum of 24 hours shall elapse prior to backfilling the remaining portion of the trench with other backfill material in accordance with Item 400, "Excavation and Backfill for Stmctures."
Type n - Backfill consists of Specification Item 400.6, "Cement Stabilized Backfill." Cement Stabilized Backfill shall be placed and compacted to ensure that all voids are filled completely.
Type m - Backfill consists of hard, durable, clean granular material that is free of organic matter, clay lumps, and other deleterious matter. Such backfill shall meet the gradation requirements shown in Table 2. The backfill material shall be placed evenly and simultaneously on both sides of the pipe to not less than 1 ft (300 mm) above the top of the pipe. The backfill shall be placed in uniform layers not exceeding 8 inches (200mm) of thickness (loose measurement), wetted if required, and thoroughly compacted between the pipe and the side of the trench. Until a minimum cover of 1 ft (300 mm) is obtained, only hand operated tamping equipment will be allowed within vertical planes 2 ft (600 mm) beyond the horizontal projection of the outside surfaces of the pipe.
In the selection of appropriate backfill material, consideration should also be given to possible migration of fines from adjacent native soil materials into the backfill. Where potential for such migration exists, separation geotextiles that meet the requirements of TxDOT Material Specification D9-6200, Type I shall be installed between the native soil and the backfill.
6.9 Protection of Pipe - No heavy constmction equipment with axle loads equal to or larger than 40-kips shall be permitted to traverse the pipe trench. If the passage of such heavy constmction equipment over an installed pipeline is necessary during
ins
constmction, compacted fill in the form of a ramp shall be constmcted to depth of one pipe diameter above the crown of the pipe.
Prior to adding each new layer of loose backfill material, until a minimum of 1 ft (300 mm) of cover is obtained, an inspection will be made of the inside periphery of the stmcture for local or unequal deformation caused by improper constmction methods. Evidence of such will be reason for such corrective measures as directed by the Engineer.
Pipe damaged by the Contractor shall be removed and replaced at no additional cost to the State.
7, Measurement This item will be measured by the linear foot (meter). Such measurements will be made between the ends of the barrel along its flow line, exclusive of safety end treatments. Safety end treatments shall be measured in accordance with item 467, "Safety End Treatment". Where spurs, branches or connections to existing pipe lines are involved, measurement of the spur or new connecting pipe will be made from the intersection of its flow line with the outside surface of the pipe into which it connects. Where inlets, headwalls, catch basins, manholes, junction chambers, or other stmctures are included in lines of pipe, that length of pipe tying into the stmcture wall will be included for measurement but no other portion of the stmcture length or width will be so included.
For multiple pipes, the measured length will be the sum of the lengths of the barrels, measured as prescribed above.
This is a plan quantity measurement Item and the quantity to be paid for will be that quantity shown in the proposal and on the "Estimate and Quantity" sheet of the contract plans, except as modified by Article 9.8. If no adjustment of quantities is required additional measurements or calculations will not be required.
Flowable backfill will not be measured, but considered subsidiary to this item.
9. Payment. The work performed and materials fumished in accordance with this Item and measured as provided imder "Measurement" will be paid for at the unit price bid for "HDPE Pipe (Type I backfill)" of the type (if required) and size specified or "HDPE Pipe (Type I, n or m backfill)" of the type (if required) and size specified. This price shall be the fiill compensation for furnishing, hauling, placing and joining of pipes; for all connections to new or existing stmctures; for moving and reusing headwalls where required, for removing and disposing of portions of existing stmctures as required; for the bedding and Type I, n or m backfill material as required, for cutting of pipe ends on skew; and for all labor, tools, equipment and incidentals required to complete the work.
Excavation and backfill above the Type I, II or m backfill will be paid for in accordance with Item 400, " Excavation and Backfill for Stmctures". Safety end treatment will be paid for in accordance with Item 467, "Safety End Treatment".
109
TABLE 1. Minimum Trench Width
Nominal Pipe Diameter inches
18 24 30 36 42 48
mm 450 600 750 900 1050 1200
Minimum Trench Width inches
44 54 66 78 84 90
mm 1100 1350 1650 1950 2100 2250
TABLE 2. Gradation Requirements for Type m BackfiU Material
Sieve No.
1 inch % inch Vi inch ^1% inch No. 4 No. 10 No.200
Percent Retained (Cumulative)
0-5 0-35 0-75 0-95
35-100 50-100 90-100
Note: Material that qualify under the following TxDOT specifications may meet the gradation requirements specified in this table.
1. ITEM 247: FLEXIBLE BASE, Grades 1,4 and 5. 2. FTEM 421: PORTLAND CEMENT CONCRETE, Coarse Aggregate Grades 4, 5, 6, 7 and 8. 3. FTEM 556: PIPE UNDBRDRAINS, Filter Material Type B
110
APPENDIX C
TYPES OF BACKFILL MATEIUALS ECONOMICALLY
AVAILABLE IN THE DISTRICTS OF TEXAS
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APPENDIX D
WORK BREAKDOWN STRUCTURE: ITEMIZING MAJOR
ACTIVITIES OF PIPE INSTALLATION PROJECTS
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cava
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pre
119
-a
c o
Q
120
APPENDIX E
ESTIMATING AS-INSTALLED COSTS OF
HDPE AND RC PIPE
121
Pip
e D
iam
eter
(in
ch
) P
IPE
AN
D T
RE
NC
H D
IME
NS
ION
FO
R H
DP
E
PIP
E I
NS
TALL
TIO
N
CO
CN
CD CO
O CO
CN
CO
Nom
inal
Pip
e D
iam
eter
(in
.)
52.7
46
.75
42.4
6 36
.07
27.8
21
.2
Pip
e O
uter
Dia
met
er (
in.)
O OJ
CO
00
co CO
in
Min
imum
Tre
nch
Wid
th (
in.),
(f
or T
ype
II &
Typ
e III
Bac
kfill)
64
.7
58.7
5 54
.46
48.0
7 39
.8
33.2
M
inim
um T
renc
h W
idth
(in
.),
(for
Flo
wab
le
Bac
kfill
) 70
.7
64.7
5 60
.46
54.0
7 45
.8
39.2
M
inim
um T
renc
h D
epth
in.
200
220
240
140
140
o
Tota
l Le
ngth
of
HD
PE
Pip
e (m
) 65
6 72
1.6
787.
2 45
9.2
459.
2 55
7.6
Tot
al L
engt
h of
HD
PE
Pip
e (ft
)
EX
CA
VA
TIO
N F
OR
HD
PE
PIP
E
INS
TALL
ATI
ON
10
73.5
926
1009
.46
954.
8201
48
421.
4789
9 29
2.10
2222
2 24
7.36
3292
2 T
otal
Vol
ume
to b
e E
xcav
ated
in C
Y (
for T
ype
II &
Typ
e III
Bac
kfill
) 77
1.79
379
706.
0215
66
6.66
0324
30
6.97
72
215.
2901
564
186.
6468
477
Tot
al V
olum
e to
be
Exc
avat
ed in
CY
(for
Fl
owab
le B
ackf
ill)
705.
7445
3 69
1.03
84
668.
2780
31
300.
8539
2 22
0.44
9140
8 19
6.76
4763
6 T
otal
Bac
kfill
Mat
eria
l R
egui
red
in C
Y (
Typ
e 1
and
II U
sed)
40
3.94
573
387.
5994
38
0.11
8207
18
6.35
213
143.
6370
75
136.
0483
192
Tot
al B
ackf
ill M
ater
ial
Reg
uire
d in
CY
(F
low
able
Fill
Use
d)
2C
Y
1..5
1.
5 C
Y
1.5
CY
>-O
>-
o T—
Exc
avat
or C
apac
ity (
Bac
khoe
l)
o 00
o
o
o
co in
CO in
Exc
avat
ion
Rat
e in
CY
/hr
13.4
1990
7 14
.420
86
13.6
4028
78
6.02
1128
4 5.
5113
6268
3 4.
6672
3192
8 T
otal
Tim
e R
egui
red
for
Exc
avat
ion
in h
r fB
ackf
ill T
voe
II or
III
Use
d)
9.64
7422
3 10
.086
02
9.52
3718
91
4.38
5388
5 4.
0620
7842
2 3.
5216
3863
7 T
otal
Tim
e R
egui
red
for
Exc
avat
ion
in h
r rF
low
able
Fill
Use
d)
122
^3
.i o U
IS H
Pip
e D
iam
eter
(in
ch)
CO
CN
CD CO
O CO
CN
CO
CA
LCU
LATI
NG
TO
TA
L B
US
Y H
OU
RS
OF
E
AC
H E
QU
IPM
EN
T I
N C
AS
E O
F H
DP
E P
IPE
IN
STA
LLA
TIO
N
2.5
CY
2.
5 C
Y
2.5
CY
2.
5 C
Y
2.5
CY
2
.5C
Y
Cap
acity
of t
he O
ther
Bac
khoe
2 10
0 10
0 10
0 10
0
o CO
100
Bac
kfill
ing
Rat
e of
Bac
khoe
2 in
CY
/hr
7.05
7445
3 6.
9103
84
6.68
2780
3 3.
0085
392
2.75
5614
26
1.96
7647
6 T
otal
Tim
e R
egui
red
for
Bac
kfill
ing
in h
rs (
Typ
e II
& I
II B
ackf
ill U
sed)
4.
0394
573
3.87
5994
3.
8011
820
1.86
3521
3 1.
7954
6343
1.
3604
831
Tot
al T
ime
Reg
uire
d fo
r B
ackf
illin
g in
hrs
(F
low
able
Fill
Use
d)
CN
CN
CN
O
O
O
Wid
th o
f Vib
rato
ry P
late
Com
pact
or o
r T
empi
ng
Ram
mer
(in
.)
1.6
1.6
CD
1.61
0.
61
0.61
R
ate
of C
ompa
ctio
n in
CY
per
min
at
8 in
Lift
per
T
wo
Com
pact
ors
7.35
1505
5 7
1983
17
6.96
1229
4 3.
1144
298
6.02
3200
56
5.37
6086
4 T
otal
Tim
e R
egui
red
for
Com
pact
ion
in h
rs
(incl
udes
tren
ch b
otto
m)
CD
CD T—
CO
CD X—
CO
CO
Leng
th o
f Tre
nch
Box
es in
ft
(Siz
e 16
by
6 ft)
^
45.1
49
.2
28.7
28
.7
34.8
5 T
otal
No.
of
Rep
etiti
on in
Ins
talla
ing
Tre
nch
Box
es
TT
-
r
TT
CO
"
Tim
e R
egui
red
for
Eac
h T
renc
h B
ox I
nsta
llatio
n in
m
in
2.73
3333
3 3.
0066
67
3.28
1.
9133
333
1.43
5 2.
3233
333
Tot
al T
ime
Reg
uire
d fo
r A
ll R
epea
ted
Tre
nch
Box
In
stal
latio
n in
hrs
32
.8
36.0
8 39
.36
22.9
6 22
.96
27.8
8 T
otal
No.
of
HD
PE
Pip
es E
ach
20 f
t Lon
g 31
.8
35.0
8 38
.36
21.9
6 21
.96
26.8
8 T
otal
No
of J
oint
s W
hen
HD
PE
Pip
e is
Use
d
t^
r--
co
CO
in
in
Tim
e R
egui
red
forT
iein
g,
Lifti
ng,
Layi
ng a
nd
Join
ginq
of
Eac
h P
ipe
in m
in
3,82
6666
7 4.
2093
33
3.93
6 2.
296
1.91
3333
33
8888838 3
Tot
al T
ime
Reg
uire
d fo
r Li
fting
, La
ying
and
Joi
ning
of
All
the
Pip
es in
hrs
15
.455
322
15.9
2596
15
.639
087
7.99
648
7.60
9747
73
7.95
8335
9 C
umul
ativ
e B
usy
hrs
of B
ackh
oe2
(Whe
n B
ackf
ill
II &
III
Use
d)
10.5
9945
7 11
.091
99
11.0
1718
2 6.
0728
546
5.14
3796
77
6.00
7149
8 C
umul
ativ
e B
usy
hrs
of B
ackh
oe2
(Whe
n F
low
able
Fill
Use
d)
123
T3 <L)
o O
Pip
e D
iam
eter
(Inc
h)
00
CN
CD CO
O CO
CN
00
CA
LCU
LATI
NG
TO
TA
L W
AG
E A
ND
EQ
UIP
ME
NT
C
OS
T F
OR
HD
PE
PIP
E I
NS
TALL
ATI
ON
P
RO
JEC
TS
CN
CN
CN
App
roxi
mat
e P
roje
ct D
urat
ion
in d
ays
(For
Typ
e II
&
II ba
ckfil
l or
Flo
wab
le F
ill)
CN
CN
CN
CN
CN
CN
Tota
l N
o. o
f E
xtra
Lab
orer
s fo
r C
ompa
ctio
n, P
ipe
layi
ng a
nd J
oini
ng
o CO
o CO
o CO
o CO
o CO
o CO
Labo
rer's
Wag
e pe
r H
our
960
960
960
480
480
480
Tot
al C
ost f
or L
abor
er's
Wag
e fo
r P
roje
ct D
urat
ion
Tim
e
in CO
in CO
in CO
in CO
o CO
o CO
Ren
tal
Rat
e of
Com
pact
or (
dolla
rs p
er d
ay)
140
140
140
o
o CD
o CD
Cos
t for
Ren
ting
Two
Com
pact
ors
for
Pro
ject
D
urat
ion
Tim
e 10
0 10
0 10
0 10
0 10
0
o o
Ren
tal
Rat
e of
eac
h 16
ft
by 6
ft t
renc
h bo
x (d
olla
rs
per
day)
60
0 60
0 60
0 30
0 30
0 30
0 C
ost f
or R
entin
g Th
ree
Tre
nch
Box
es fo
r P
roje
ct
Dur
atio
n
CD 00
CD in
CD in
CD in
CD
CD
Hou
rly R
enta
l R
ate
of B
ackh
oel
(1 C
Y,
1.5
CY
or 2
C
Y B
ucke
t C
apac
ity)
100
100
100
100
100
100
Hou
rly R
enta
l R
ate
of B
ackh
oe2
(2.5
CY
Buc
ket
Cao
acitv
) 35
.41
35.4
1 35
.41
35.4
1 35
.41
35.4
1 H
ourly
Wag
e of
81
Cre
w (
1 T
ract
or o
pera
tor
1 la
bore
r) i
nvol
ved
with
Bac
khoe
s 12
1.41
91
.41
91.4
1 91
.41
81.4
1 81
.41
Hou
rlly
Tot
al I
nsta
llatio
n C
ost
Invo
lved
with
B
ackh
oel
135.
41
135.
41
135.
41
1
135.
41
135.
41
135.
41
Hou
rlly
Tot
al I
nsta
llatio
n C
ost
Invo
lved
with
B
ackh
oe2
1942
.56
1462
.56
1462
.56
731.
28
651.
28
651.
28
Tot
al C
ost
Invo
lved
with
Bac
khoe
l fo
r P
roje
ct
Dur
atio
n T
ime(
All
Tvo
es o
f B
ackf
ill)
2166
.56
2166
.56
2166
.56
1083
.28
1083
.28
1083
.28
Tot
al C
ost
Invo
lved
with
Bac
khoe
2 fo
r P
roje
ct
Dur
atio
n T
ime(
AII
type
s of
bac
kfill)
124
t 3 <D
.1 O
U
x: o
(D <4—•
CD
E ro
b <D CL
Q-
CO ^r
CN -^
CD CO
o CO
CN
OO
- 1
RIA
UJ
LL
MA
T
KFI
o
AIL
AB
LE B
A(
IFA
V
UN
IT P
RIC
E C
o
o
o
o
o
o
Soil
ativ
e 1
rice
of N
U
nit P
I
i n CO
i n 0 0
i n CO
m CO
i n 00
i n CO
) Fill
($/
CY
)
X3
^
Type
1 or
Flo
\ ac
kfill
ric
e of
B
Uni
t P
CN CO
CN CO
CN CO
CN CO
CN CO
CN CO
.id o
Stab
Ba
men
t Ty
pe I
I or
Ce
Y)
ackf
ill
B($
/C
CQ c: M- o O N
0) (D o o
' t _ ' l —
Uni
tP
Low
P
o CD
O CO
o CD
O CD
O CD
O CD
o
Sta
b B
e m
ent
Type
11
orC
e ($
/CY
) ac
kfill
Zo
ne
rice
of B
m
Pric
e U
nitP
M
ediu
CO •"t"
CO • * "
CO t —
CO T —
OO
"
CO T —
CO
exa
1 -
Pric
e in
ic
al
CL
lex
Bas
e ($
/CY
), Ty
ric
e of
F
Uni
tP
o ''"
o ~
o X —
o T —
o "
o T ~
^
(Lo^
z =
ar B
ackf
i in
uh
i U
Typ
e 111
or
Gi
ackf
ill
rice
of
B
Un
itP
P
rice
)
i n x ~
i n • * "
i n T —
m t —
i n • ^
i n T —
ical
Ty
p
—"
ir B
ackf
i 1
ro 13
c cn
Typ
e III
or
Gri
ackf
ill
rice
of B
i U
nit
P
Pri
ce)
- 1
AC
KF
IL
m a: o
TAL
CO
ST
F(
GT
O
ULA
TIN
•R
IAL
CA
LC
MA
TE
_ r». CD CO
i n
-^ CD CO
CO
-^ CD
f ^ Oi iri
.,_ 9.
7
CO
cd
per
»the
Site
TS 0)
>E P
ipe
Supp
li
Q X
Uni
tP
CO h -
^ 0 0 o " CN
CN r--CNJ
197
CN
CO CD
5.2
O) CN i n • « ~
-^ CN
" CO CO CO r^
CN CO CO od i n "^ ^r
CO 0 0 CN
i n CO
Pipe
s ($
) C
ost
Of H
DP
E
Tota
l 1
h -0 0 CO
iri CO CO
CO
i n CD
iri
294
CO
h -T t
0.0
— CO CN CO
T —
CO CD C3J CO 0 0 i n
.^ i n
C3J o CN CN
r>~ o T —
TT
1156
<D CL
EP
I
Q-
d fo
r H
D
(D ? T3 3 CD o r W
ill M
ater
ial
Re
(g$8
5/C
Y is
L
Bac
kf
e Fi
ll C
ost f
or
Flow
abI
_ c ro o
i n CN 0 0 CO 0 0 i n CN CN
CO CN CO
211
CN
r C35
4.8
0 0 CO r— CN
i n i n CN CO h- CN CD C3>
i n CN
CO
f i n o
" CN h -
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128
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available for research purposes. Permission to copy this thesis for scholarly
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It is understood that any copying or publication of this thesis for financial gain
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