CHAPTER 20...CHAPTER 20 Infiltration Facility Design and Subsurface Drainage NYSDOT Geotechnical...

NYSDOT Geotechnical Page 20-1 October 3, 2013

Design Manual

GEOTECHNICAL DESIGN MANUAL

CHAPTER 20

INFILTRATION FACILITY DESIGN

AND SUBSURFACE DRAINAGE

NYSDOT Geotechnical 0-2 October 3, 2013

Design Manual

(Intentionally left blank)

Table of Contents


Design Manual

20.1 OVERVIEW ............................................................................................................... 20-4

20.1.1 Recharge.......................................................................................................... 20-4

20.2 GEOTECHNICAL INVESTIGATION FOR INFILTRATION FACILITIES ........... 20-4

20.3 GEOTECHNICAL DESIGN OF INFILTRATION FACILITIES .............................. 20-4

20.3.1 Parameters for Geotechnical Design of Infiltration Facilities ......................... 20-9

20.3.1.1 Subsurface Explorations and Permeability Tests ................................ 20-9

20.4 FILTER DESIGN FOR GROUNDWATER DRAINS ............................................. 20-11

20.4.1 Basis for the Use of Granular Filters ............................................................ 20-11

20.4.2 Design of Granular Filters ............................................................................. 20-11

20.4.3 Filter Criteria ................................................................................................. 20-12

20.4.4 Granular Filters at Pipe Joints, Holes, and Slots ........................................... 20-12

20.5 SUBSURFACE DRAINAGE ................................................................................... 20-13

20.5.1 Underdrains ................................................................................................... 20-13

20.5.2 Edge Drains ................................................................................................... 20-14

20.5.2.1 Preformed Composite Edge Drains................................................... 20-16

20.6 REFERENCES ......................................................................................................... 20-19

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Infiltration Facility Design and Subsurface Drainage


Design Manual

20.1 OVERVIEW Infiltration facility design includes the design of basins, trenches and other water quality best

management practices (BMP’s) designed to encourage infiltration and pollutant removal of

stormwater runoff before it enters back into the subsurface water supply. Geotechnical design of

infiltration facilities not only includes assessment of the groundwater regime, soil stratigraphy,

and hydraulic conductivity of the soil as it affects the functioning of the infiltration facility, but

also involves an evaluation of the geotechnical stability of the facility (e.g., slope stability, affect

of seepage forces or soil piping at adjacent structures and slopes, and design of fills that control

the retention, diversion, or discharge of the collected stormwater).

20.1.1 Recharge

Allowing precipitation to replenish the groundwater supply, via infiltration or percolation, is an

important phase in the natural hydrologic cycle. The groundwater levels and hence, groundwater

supplies, generally increase in relationship to the amount of precipitation and the hydraulic

conductivity of the subsurface materials. The hydrologist or groundwater geologist refers to

water entering the aquifer as “recharge” bringing rise to the commonly used term “recharge

basin”.

20.2 GEOTECHNICAL INVESTIGATIONS FOR INFILTRATION FACILITIES The requirements of a geotechnical field investigation, the evaluation of the soil properties, and

groundwater quality requirements, and the necessary design elements for an infiltration practice

are discussed in the Geotechnical Design Procedure (GDP-8) Design, Construction, and

Maintenance of Recharge Basins and in the NYS DEC’s Stormwater Management Design

Manual (2010).

For geotechnical stability, the site investigation and design requirements provided in NYSDOT

GDM Chapters 2, 10, 12, and 13 are applicable.

20.3 GEOTECHNICAL DESIGN OF INFILTRATION FACILITIES

Unsaturated Flow vs. Saturated Flow

Since stormwater infiltration systems are designed to completely drain within 48 hours,

groundwater replenishment by means of recharge basins, as shown in Figure 20-1, or other

infiltration practices, generally takes place through unsaturated flow conditions in the soil zone

above the groundwater level. The process of water flow through an unsaturated soil is termed as

infiltration. Infiltration is an unsteady-state process of flow, meaning that the flow rate varies

with time under a constant head of water (e.g. infiltration flow rate will change even if the basin

remains full of water). When a stormwater infiltration basin experiences very long rain events

that will keep water in the basin for several days, the infiltration flow rate below will actually

decrease until the rate of flow approaches what occurs within a saturated soil condition. At soil

saturation, the flow is called percolation, and the rate of flow reaches its slowest value. However,

https://www.dot.ny.gov/divisions/engineering/technical-services/technical-services-repository/GDP-8b.pdf

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soil saturation below an infiltration practice is rarely achieved since an extraordinarily long rain

event is required.

If infiltration practices are chosen to address stormwater runoff, the Designer will need to

evaluate the probability of soil saturation below the practice. Therefore, the Designer will need

reliable information on the seasonal, high groundwater elevation or the presence of a protected

aquifer, the possibility of a temporary, perched water level or a deep frost layer, the soil gradation

for an extended depth below the bottom of the infiltration facility and the presence of any

shallow bedrock or impermeable soil layers at the proposed site.

Infiltration flow is complex and encompasses gravity flow and flow enhancements through

capillary suction and diffusion. This combination of flow methods explains why unsaturated flow

is faster than saturated flow. In design computations, the average rate of flow in unsaturated soil

conditions is represented by use of a hydraulic conductivity factor and a hydraulic diffusivity

factor. Although the flow is more complex, the same engineering principles can be applied to

unsaturated flow as is used for saturated flow. Therefore, the hydraulic conductivity factor and

the hydraulic diffusivity factor can be reliably estimated after first determining a soil’s coefficient

of permeability under saturated conditions.

Therefore, an essential element to be determined in the geotechnical investigation is the

coefficient of permeability (ks) of the soils underlying an infiltration practice. Permeability (ks)

represents the capacity of a saturated, porous material for transmitting a fluid without damage to

the structure of the medium (also known as saturated hydraulic conductivity).

The coefficient of permeability (ks) in a soil layer is best determined by performing percolation

tests or “rising head” tests near the proposed base elevation(s) of the stormwater infiltration

practice. The accuracy of the permeability value is dependant on saturated soil conditions being

ensured through soaking of the soil, or by utilizing a drill hole for a “rising-head” test that

extends below the water table. However, for soils with very high infiltration flow rates and very

deep water tables, soil saturation during the percolation test may be difficult to achieve. Under

such conditions, the designer may be able to obtain a reasonable value of the soil’s coefficient of

permeability by use of a laboratory procedure or by performing a “falling-head” test in a shallow

drill hole.

Design Methods for Infiltration Practices

The NYSDOT makes use of two design procedures to develop stormwater infiltration practices.

One procedure allows design of an infiltration practice that can address the stormwater runoff

from multi-year storm events. The alternate procedure allows design of an infiltration practice

that can address only the annual stormwater runoff event and incorporates by-pass outlets for

multi-year storm events.

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An infiltration practice capable of handling multi-year storm events is often used at sites which

display very high infiltration flow rates (generally an infiltration flow rate of 15 in./hr, or greater)

and which have soils with less than 10% fines and a relatively deep water table. This design

procedure is presented in the Geotechnical Design Procedure (GDP-8) Design, Construction, and

Maintenance of Recharge Basin is used.

For sites which display moderate to low infiltration flow rates, the infiltration practice is

developed to handle the annual stormwater runoff event using the procedure given in NYS

DEC’s Stormwater Management Design Manual (2010). This design procedure is used at sites

where the coefficient of permeability can be accurately measured in the field (typically 15 in./hr

> ks > 0.5 in./hr), and have soils with no more than 40% fines and a moderately deep water table.

Infiltration practices cannot be used when the infiltration flow rate is less than 0.5 in./hr. The

designer must consider that an infiltration practice is intended to provide a recharge of the

groundwater and also act as a sediment and pollutant filter of the stormwater. To accomplish the

filtering requirement, a pre-treatment fore bay is generally required upslope of the infiltration

practice.

Figure 20-1 Groundwater Replenishment Through a Recharge Basin


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Multi-Year Storm Infiltration Practice - Feasibility and Preliminary Design

When considering an infiltration practice that can handle a multi-year storm event, two types of

recharge methods may be proposed - surface or subsurface.

1. Surface recharge basins should be designed in accordance with Geotechnical Design

Procedure (GDP-8) Design, Construction, and Maintenance of Recharge Basins. GDP-8 is

intended to serve as a guide for determining feasibility, design, basin size, construction, and

maintenance requirements for high infiltration flow rate facilities. Pre-treatment of 100% of

the stormwater runoff volume must be addressed by methods discussed in NYS DEC’s

Stormwater Management Design Manual (2010).

Basin recharge is feasible wherever the following conditions exist:

• The soils, excluding the top 5 ft. of surface soil, are relatively permeable, and contain

less than 5% of fine grained soils. Obtaining an accurate coefficient of permeability

from percolation tests at these sites is often difficult and the use of a “rising-head”

drill hole permeability test can also be difficult since the water table is typically

located far below the base of the infiltration practice,

• Unsaturated conditions exist to a considerable depth below the surface. Infiltration

cannot occur if a soil is already saturated by permanent groundwater. For a design to

be valid, a good rule-of-thumb is that the depth of unsaturated soil below the

proposed basin floor is greater than 25 percent of the peak basin operating head with a

minimum separation of 5 feet from the seasonally high water table or any shallow

bedrock. The peak basin operating head, H, is defined as the maximum depth of water

permissible for the proposed basin,

• Unsaturated soils are not laterally confined, i.e. they have the capacity for water to

move and store horizontally. It is very helpful if sufficient space is available for

placing multiple basins in the project vicinity. Maximum use should be made of the

surrounding natural terrain, interchange loop channels between infiltration practices

and other project site depressions. This can allow substantial runoff volumes to be

disposed of by infiltration in a very small space,

• The infiltration flow rate of the underlying soils is sufficiently high to allow full

drainage of the basin within 48 hours,

• The basin will be located at least 100 feet away from water supply wells, and

• Cannot be located within a fill layer.

2. Subsurface recharge can be accomplished through the use of leaching basins. "Design of

Leaching Basins", Research Report 157, should be used as a source of information regarding

leaching basin design.

Leaching basins resemble isolated pits more than recharge basins, and are designed to

function differently than recharge basins. Leaching basins are usually cylindrical and deep,

often 10 to 20 ft. deep, with a 4 to 10 ft. internal diameter (see Figure 20-2). The walls are 4

in. thick concrete with rectangular windows cut in them below 5 ft. to allow water passage.



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The basin’s lower portion is surrounded by 2 ft. thick aggregate. This aggregate is covered by

a filter material to prevent overlying soil outside the basin from washing down into the

gravel. The bottom of the basin has no concrete floor, but is open to an underlying 2 ft. of

aggregate. Pre-treatment of 100% of the stormwater runoff volume must be addressed by

methods discussed in NYS DEC’s Stormwater Management Design Manual (2010).

Leaching Basin recharge is feasible wherever the following conditions exist:

• Unsaturated soils are not laterally confined, i.e. they have the capacity for water to

move horizontally and vertically,

• The permeability of the underlying soils is sufficiently high to allow full drainage of

the basin within 48 hours,

• The leaching basin will be located at least 100 feet away from water supply wells and

at least 10 feet from any structures,

• Typically will not be used to drain a surface area larger than one acre,

• Minimum separation of 4 feet from the seasonally high water table or any shallow

bedrock, and

• Cannot be located within a fill layer.

Figure 20-2 Leaching Basin

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Annual Storm Runoff Infiltration Practice - Feasibility and Preliminary Design

Stormwater infiltration practices designed to handle the annual stormwater runoff volume should

be designed in accordance with NYS DEC’s Stormwater Management Design Manual (2010).

This manual is intended to serve as a guide for determining the feasibility, design, type and size,

construction, and maintenance requirements for moderate to low infiltration flow rate facilities.

The infiltration practice is sized based on an assumption that saturated flow (the slowest rate of

water flow in a soil) will occur. Therefore, the coefficient of permeability, rather than the

hydraulic conductivity factor, is used in the design of the infiltration practice. This approach

allows for a slightly conservative capacity of the infiltration practice and helps ensure that the

practice will fully drain within 48 hours.

Pre-treatment of between 25% to 100% of the stormwater runoff volume, and the by-pass of

larger storm volumes, must be addressed by methods discussed in NYS DEC’s Stormwater

Management Design Manual (2010).

Feasibility of recharge at sites with moderate to low infiltration flow rates:

• Underlying soils must have an infiltration flow rate of at least 0.5 in./hr,

• Soils should have a clay content of less than 20% and clay/silt content of less than

40%,

• Infiltration practice cannot be located in fills or in areas with slopes greater than 15%,

• The base of the infiltration practice (basin, trench, or dry well) should have a

minimum separation of 3 feet above the seasonally high water table or a bedrock layer

(4 feet separation if over a sole source aquifer), and

• The infiltration practice will be designed to infiltrate between 90 to 100% of the

annual stormwater runoff event and have an overflow by-pass capacity for at least a

10-year storm event.

20.3.1 Parameters for Geotechnical Design of Infiltration Facilities

20.3.1.1 Subsurface Explorations and Permeability Tests

Permeability Tests

The following test procedures provide the Designer with an estimation of the coefficient of

permeability that can also be used to develop the hydraulic conductivity factor and the hydraulic

diffusivity factor:

• Specific Surface Analysis: Geotechnical Test Procedure (GTP-5) Test Procedure for

Specific Surface Analysis describes the method for determining the specific surface of soil

solids from grain size distribution data. It also describes the use of the specific surface in

calculating the coefficient of permeability and other soil properties.

https://www.dot.ny.gov/divisions/engineering/technical-services/technical-services-repository/GTP-5b.pdf

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Specific surface is the particle surface area contained in a unit volume of soil solids. The

particle surface area includes only the external particle surface (the internal porosity of

individual particles is neglected). The estimated, saturated permeability of the cohesionless

granular material can be determined from the specific surface of solids.

The soil samples obtained from the subsurface exploration is tested. The test method

involves:

• Performing a grain size analysis of the soil specimen,

• Examining the shape characteristics of the grains contained in each sieve interval,

and

• Calculation of the specific surface.

Limitations: There is a limitation on the test procedure. If the soil sample contains more

than 5% passing the No. 200 sieve, the specific surface analysis is not performed.

• Drill Hole Infiltration Test: A drill hole infiltration test is detailed in Appendix D of the

NYS DEC Stormwater Management Design Manual. Additional information on drill hole

permeability tests are described in NAVFAC Design Manual DM-7.1 Soil Mechanics.

The drill hole infiltration test shown in the NYS DEC’s Stormwater Management Design

Manual (2010) is a “falling-head” drill hole test that provides a reliable estimation of the

saturated permeability when the infiltration flow rates are moderate to moderately low

and the soils contain more than 5% fine grained particles. The test is intended for

relatively shallow infiltration practices where excavation to the testing level is practical.

For sites with very high infiltration flow rates, the measured rates may be unreliable for

determining the coefficient of permeability (ks) due to the surrounding soil being unable

to become saturated prior to and during testing. For very low infiltration rates, the

coefficient of permeability will be too low to allow adequate infiltration flow.

Additional drill hole permeability tests presented in NAVFAC Design Manual DM-7.1

make use of a “rising-head” test that is performed below the water table. This approach

provides more accurate results than the “falling-head” test, but the soil must also be

moderately permeable and the water table located within soil conditions similar to the

base of the infiltration practice.

The factors affecting the performance and applicability of the drill hole permeability test

include:

• Depth of the water table level,

• Type of material (rock or soil),

• Depth of the test zone,

• Permeability of the test zone, and

• Heterogeneity and anisotropy of the test zone.

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To account for these factors, it is necessary to isolate the test zone at various depths.

Typically, to identify the subsurface strata, two subsurface explorations should be

progressed within 5 ft. of each other. The first subsurface exploration would identify the

soil strata by obtaining continuous samples. The exploration (usually a test hole

progressed with continuous Standard Penetration Testing) should be progressed to a

sufficient depth to locate and determine the extent and properties of all soil, water, and

rock strata that could affect the performance of the feature. Typically, the minimum depth

of the exploration should be at least 10 ft., or to a depth equal to the basin’s full height,

whichever is greater, below the proposed base elevation of the infiltration practice. The

second subsurface exploration would be progressed to perform the permeability test.

If subsurface explorations are not proposed and the appropriate equipment is obtainable, a more

common way of determining the coefficient of permeability at the site is a percolation test.

Percolation Test: Percolation is defined as the gravity flow of groundwater through the

fully saturated pore spaces in rock or soil. A percolation test is typically used as a test to

determine the suitability of a soil for the installation of a domestic sewage-disposal

system, in which a hole is dug and filled with water and the rate of water-level decline is

measured. The Department utilizes percolation test data to determine infiltration rates.

Percolation tests are described in NYSDOT GDM Chapter 4.

20.4 FILTER DESIGN FOR GROUNDWATER DRAINS

20.4.1 Basis for the Use of Granular Filters

Water seeping through a soil produces seepage pressures which can dislodge soil particles in the

direction of seepage, when the force is sufficient. If the soil does not have sufficient cohesion or

the individual soil particles are not sufficiently heavy or encircled to resist the seepage force, they

can be displaced. If the soil is well graded and contains a sufficient proportion of particles that

are too large for the seepage forces to move, a natural filter layer may develop as some of the

smaller particles are trapped between the larger particles and thus, erosion due to seepage should

stop. In the absence of coarse particles erosion may start near the ground surface and work its

way progressively back along the path of the seepage flow. Examples of this occurrence are some

types of cut-slope sloughs and piping under or through dams. Criteria have been developed for

the determination of the required particle distribution of a granular filter material, which when

placed over, or adjacent to, a soil with a known problematic grain size distribution, will prevent

erosion of the soil.

20.4.2 Design of Granular Filters

A filter material must meet two basic requirements:

1. The filter material must be fine enough to prevent infiltration of the material from which

drainage is occurring, and

2. The filter material must be much more permeable than the material being drained.

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20.4.3 Filter Criteria

• Retention or Stability Criterion – see NYSDOT GDM Chapter 7.

The 15% size (D15) of a filter material must be not more than four or five times the 85% size

(D85) of a protected soil. The ratio of D15 of a filter to D85 of a soil is called the piping ratio. This

criterion prevents the migration of fines and clogging.

• Permeability Criterion – see NYSDOT GDM Chapter 7.

The 15% size (D15) of a filter material should be at least four or five times the 15% size (D15) of

a protected soil.

The intent of criterion 2 is to guarantee sufficient permeability to prevent the buildup of large

seepage forces and hydrostatic pressures in filters and drains.

The two criteria are expressed as follows:

Equation 20-1

)(

)(54

)(

)(

15

15

85

15

soilD

filterDto

soilD

filterD

An additional criterion required by the US Army Corps of Engineers to ensure that the gradation

curve of a filter aggregate will be somewhat parallel to the curve for a soil is:

Equation 20-2

25)(

)(

50

50

soilD

filterD

20.4.4 Granular Filters at Pipe Joints, Holes, and Slots

When pipes are embedded in granular filter material, the ends of the pipe backfill should be

sealed by lower permeability soils and the filter materials in contact with pipes must be coarse

enough to not enter joints, holes or slots. The US Army Corps of Engineers and the US Army et

al. use the following criteria for gradation of granular filter materials in relation to slots and holes

along the pipe:

For circular holes:

Equation 20-3

0.1)(85

diameterhole

filterD

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For slots:

Equation 20-4

2.1)(85

widthslot

filterD

20.5 SUBSURFACE DRAINAGE

20.5.1 Underdrains

Underdrains are narrow trenches filled with clean aggregate filter material having a gradation that

is both pervious to water and capable of protecting the trench from infiltration by the surrounding

soil. Commonly, the flow capacity of the underdrain is enhanced by including a perforated or

slotted pipe within the aggregate filter material.

Underdrains lower or remove the subsurface water level below pavements or structures by means

of gravity flow. To function, they must be continuously sloped to an outlet, such as a drainage

channel or a closed drainage system. If designed and located appropriately, no intercepted water

is allowed to sit within the underdrain for long periods (more than 48 hours) and this helps to

ensure that any transported sediments do not settle out and block low points. The installation’s

effect on the adjacent site conditions depends on the surrounding area’s permeability and the

depth to which the groundwater level must be lowered. See NYSDOT GDM Chapter 7 for design

of underdrain filter material gradation. Installation details are provided on Standard Sheet 203-05

Installation Details for Corrugated and Structural Plate Pipe and Pipe Arches.

The Regional Geotechnical Engineer should be consulted to locate underdrains and their outlets

during design. Because underdrains are relatively expensive, good engineering requires

discriminate application. Ideally, the invert of the underdrain trench should be at least 4 ft. lower

than the nearest edge of pavement or ground surface. In areas where this can not be accomplished

due to shallow rock, water, or underdrain outlet elevations, considerations should be given to

constructing an underdrain trench as close to this depth as reasonably possible.

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Figure 20-3 Underdrain Installation Detail

(NYSDOT HDM Chapter 9)

20.5.2 Edge Drains

Edge drains are designed to remove water from the pavement section by means of gravity flow.

To function, they thus must be continuously sloped to an outlet, such as a drainage channel or a

closed drainage system, to ensure that no intercepted water is allowed to accumulate and that any

transported sediments do not settle out and block low points.

Edge drains for NYSDOT pavement designs extend 12 in. below the subgrade surface, thereby

also functioning as an underdrain.

Edge drain details and location depend on the highway geometry (e.g. superelevated, sag, etc.) as

well as pavement section (e.g. curbing, permeable base, etc). The edge drain should normally be

placed at the pavement's interface with the shoulder or curb since a change in the subbase

thickness at these locations often leads to subsurface water buildup and pavement damage.

Several studies had been performed by numerous State’s and the FHWA since the 1990’s to

determine how effective underdrain system were in minimizing damage to pavements and which

subsurface drainage systems performed better. The most comprehensive study was Project 1-34

by the National Cooperative Highway Research Program. In summary, the study revealed that:

1. both concrete and asphalt pavement systems, only a few years after construction, can

absorb up to 25 to 40% of a short rain event and underdrain and minor infiltration can

effectively remove most of this water within 24 hours,

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2. The more flexible a pavement system is, the more its performance relies on effective

subsurface drainage,

3. Connecting a permeable treated base layer to an underdrain significantly improves the

pavement’s long term performance,

4. Blocked underdrains can significantly contribute to the poor performance of a pavement,

5. Daylighting the outside edge of a subbase layer or a treated permeable base layer, in lieu

of connecting these layers to an underdrain, allows even better long term pavement

performance, and

6. Geotextiles wraps around an underdrain can impact its effectiveness within as little as 7

to 10 years.

Locations along the highway where concentrations of subsurface water may require underdrains

are sometimes difficult to predict during design, but some obvious locations for underdrains are:

1. Areas of existing surface seepage or saturation where a new highway is to be located,

2. Where the pavement parallels the base of a long or tall hill, or

3. On very long downhill grades where flow from infiltrated runoff and seepage zones tends

to follow the direction of the pavement. On long, downhill grades, transverse underdrains

cut diagonally across the travel lanes can improve the effectiveness of the underdrain

system.

Figure 20-4 Edge Drain in a Curbed Pavement Section


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The edge drain should intercept water from the highest water-bearing layer of the pavement

section. In flexible pavements, this water is usually encountered near the bottom of the asphalt

base course. In rigid pavements, it is usually found at the top of the subbase course. Also, since

the pavement’s subbase materials are often permeable, water can be located at the bottom of the

subbase layer. Typical edge drain installations for rehabilitation and restoration of conventional

pavements are shown in the see NYSDOT Comprehensive Pavement Design Manual.

In pavement sections that include a treated permeable base layer, the top of the edge drain should

be in full contact with the bottom of the permeable base at the lowest levels of its cross-section.

Again, the NYSDOT Comprehensive Pavement Design Manual provides edge drain details for

full-depth PCC over permeable base and edge drain details for full-depth HMA with permeable

base.

Edge drains must be provided with lateral outlets to the roadway ditch or to appropriate

structures in a closed storm-drain system. In practice, edge drains are normally placed in a trench

dug after subbase construction. This method requires removing subbase and subgrade material,

but it is used for ease of construction because it achieves uniform compaction of the roadway

section, and adequately confines the underdrain filter material.

20.5.2.1 Preformed Composite Edge Drains

Preformed edge drains are also available, usually consisting of a ribbon of corrugated or dimpled

plastic sheathed in an underdrain geotextile. The ribbons, referred to as Prefabricated Composite

Edge Drains (PCED) may be 2 ft. to 3 ft. taller, or taller, to ensure full contact with the pavement

subbase and subgrade layers. PCED are installed by a trenching machine that excavates a slit-

trench, places the edge drain, and backfills with fine, coarse aggregate, and compacts the trench

in one pass. PCED are particularly advantageous where an open trench is not wanted, or for very

long installations of pavement drains.

Although the installation process is rather quick and simple, inspection of the installation and

backfill operations are critical. To prevent cracking and settlement at the pavement surface above

the trench, the Prefabricated Composite Edge Drain must be placed tightly against one side of the

trench, without bends or folds, and the fine, coarse aggregate backfill must reach to the base of

the trench, be compacted in at least 2 lifts, and must be placed to match the subbase surface

above the top edge of the Prefabricated Composite Edge Drain. Since compaction of superpave

asphalt commonly requires a 4 foot wide placement, the installation of Prefabricated Composite

Edge Drains is now performed through the top of the exposed subbase layer. The asphalt

pavement is then placed afterwards.

See the NYSDOT Comprehensive Pavement Design Manual for complete guidance for PCED

installation and use.

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Figure 20-5 Preformed Composite Edge Drain: Installation with Stone Backfill

Adjacent to Full Depth Asphalt Pavement


Figure 20-6 Preformed Composite Edge Drain: Installation with Stone Backfill

Adjacent to Concrete Pavement


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Figure 20-7 Preformed Composite Edge Drain: Installation with Existing Suitable

Backfill Material Adjacent to Asphalt Pavement


Figure 20-8 Preformed Composite Edge Drain: Installation with Existing Suitable

Backfill Material Adjacent to Concrete Pavement


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20.6 REFERENCES

Cedergren, H.R., Seepage, Drainage, and Flow Nets, Third Edition, John Wiley and Sons, Inc.,

1989.

Department of Environmental Conservation, New York State Stormwater Management Design

Manual, Center for Watershed Protection, August, 2010.

Department of the Navy, Naval Facilities Engineering Command (NAVFAC), Soil Mechanics,

Design Manual 7.1, May, 1982.

Geotechnical Engineering Bureau, Design, Construction, and Maintenance of Recharge Basins,

Geotechnical Design Procedure GDP-8, New York State Department of Transportation, Office of

Technical Services,

https://www.dot.ny.gov/divisions/engineering/technical-services/technical-services-

repository/GDP-8b.pdf

Geotechnical Engineering Bureau, Test Procedure for Specific Surface Analysis, Geotechnical

Test Procedure GTP-5, New York State Department of Transportation, Office of Technical

Services,

https://www.dot.ny.gov/divisions/engineering/technical-services/technical-services-

repository/GTP-5b.pdf

Johnson, A.I, Filter Pack and Well Screen Design, United States Department of the Interior,

Geological Survey, Hydrologic Laboratory, 1963: http://pubs.usgs.gov/of/1963/0060/report.pdf

Lechter, V., Saridis, Y., Lu, J., Design of Leaching Basins, Federal Highway Administration,

New York State Department of Transportation, Final Report FHWA/NY/RR-92/157, 1992.

New York State Comprehensive Pavement Design Manual (CPDM), Department of

Transportation, Office of Technical Services,

https://www.dot.ny.gov/portal/page/portal/divisions/engineering/design/dqab/cpdm

New York State Highway Design Manual (HDM), Department of Transportation, Design Quality

Assurance Bureau,

https://www.dot.ny.gov/divisions/engineering/design/dqab/hdm

Uhland, R.E., O’Neal, A.M., Soil Permeability Determination for Use in Soil and Water

Conservation, SCS-TP-101, United States Department of Agriculture, Soil Conservation Service,

Washington, D.C., 1951.

Weaver, R. J. Recharge Basins for Disposal of Highway Storm Drainage, Research Report 69-2,

Engineering Research and Development Bureau, New York State Department of Transportation,

May 1971.





http://pubs.usgs.gov/of/1963/0060/report.pdf

https://www.dot.ny.gov/portal/page/portal/divisions/engineering/design/dqab/cpdm

https://www.dot.ny.gov/divisions/engineering/design/dqab/hdm

CHAPTER 20...CHAPTER 20 Infiltration Facility Design and Subsurface Drainage NYSDOT Geotechnical...

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Transcript of CHAPTER 20...CHAPTER 20 Infiltration Facility Design and Subsurface Drainage NYSDOT Geotechnical...