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Preliminary Design Report____________Rehoboth, New Mexico

Jesse Singer, Scott Malefyt, Jeannine Keller, Scott Hekman and Neil De Wit

Water Management Plan for Rehoboth, New Mexico

May 2007


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TABLE OF CONTENTS

I. INTRODUCTION 4

II. PERMITS 6

III. SITE (REHOBOTH AND GALLUP AREA) 9

IV. SANITARY COLLECTION 12

V. BASIS OF WATER PRODUCTION DESIGN 13

VI. LIFT STATION 16

VII. PRETREATMENT 17

VIII. MEMBRANE BIO-REACTOR 19

IX. REVERSE-OSMOSIS MEMBRANES 20

X. POST-TREATMENT 22

XI. SOLIDS HANDLING 23

XII. OVERALL WATER PRODUCTION COSTS 25

XIII. BIOGAS TREATMENT 26

XIV. ELECTRICAL AND INSTRUMENTATION 27

XV. PLANT BUILDINGS 27

XVI. DRINKING WATER DISTRIBUTION 27

XVII. STORMWATER MANAGEMENT 29

XVIII. CONCLUSIONS AND RECOMMENDATIONS 30


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Table of Tables

Table 1 School Lot Appropriations

Table 2 Sanitary Sewer Cost Summary

Table 3 Average Daily Flow (ADF) Summary

Table 4 Water Production Plant Flows

Table 5 Water Production Equipment

Table 6 Zenon Model Removal Estimates

Table 7 MBR Effluent Quality

Table 8 Overall Water Production Costs

Table 9 Cost Comparison

Table 10 Watermain Cost Data

Table 11 Storm Sewer Culvert Cost Data

Table 12 Total Combined Cost Estimate

Table of Figures

Figure 1 Arial View of Rehoboth with Edge of Gallup to the Far West

Figure 2 Production Plant Schematic

Figure 3 Watershed Delineation with zones indicated

Figure 4 RRMF Development Plan

Figure 5 Rehoboth Christian School Development Plan

Figure 6 Elevation View of Lift Station

Figure 7 Pretreatment Schematic

Figure 8 Z-MOD-L Basic Layout

Figure 9 GE Osmonics PRO 150

Figure 10 Ultraviolet Treatment Schematic


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I. INTRODUCTION

1.1 The TeamTeam Desert Oasis is a five member team, consisting of BSE Civil/Environmentalstudents who are working to design a full water management system for theRehoboth Red Mesa Foundation (RRMF) and Rehoboth Christian School (RCS) inNew Mexico for a Calvin Engineering senior design project. Team members are:Neil De Wit, Jeannine Keller, Jesse Singer, Scott Hekman, and Scott Malefyt. TeamOasis chose this as a senior design project due to their interests in environmentaland hydraulic engineering and their desire to be in continual service to others andGod.

1.2 The GoalsThe goal of the project was to design and give alternatives for a functional watermanagement system for the Rehoboth area (shown in Figure 1). The Rehoboth areaincludes both the school and the RRMF lands. Requirements include providingfeasible solutions to drainage, drinking water, and sanitary sewer issues for existingconditions and future expansion in the area. The system must be cost effective andprovide sufficient capacity to the area. Expansion plans, topography, desires of theschool and RRMF, and ethics will control aspects of the design.

1.3 Executive SummaryRehoboth, New Mexico is located in McKinley County on the northwest side of thestate, just a few miles east of Gallup, NM. There are two organizations that own landin Rehoboth and thereby act as separate entities: the RCS and the RRMF. Bothorganizations plan to develop large areas of land over the next couple of decades.These developments are expected to bring in residents, businesses and revenuethat will enable Rehoboth to grow as a community and support ministry programs.Presently, however, Rehoboth is lacking both a water treatment process and astructured management of storm water, leading to a limited amount of availableclean drinking water as well as recurrent flooding.

Figure 1: Aerial View of Rehoboth with the edge of Gallup to the far West.

To satisfy Rehoboths wastewater and drinking water needs for its estimated future5,000 person population, it is necessary to provide water treatment within

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1000 ft


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Rehoboths limits. A complete water production system comprised of the three keysteps: primary treatment, secondary treatment and disinfection has been chosen fordesign. Primary treatment utilizes a membrane bioreactor (MBR) to filter influentwastewater and is followed by a secondary treatment step consisting of reverseosmosis membranes (RO). Disinfection will be completed with ultraviolet (UV)technology. Though membrane treatment is a relatively new technology, several

cities have implemented membrane treatment with great success. 1 The basic layoutof the plant design is modeled in Figure 2.

Figure 2: Production plant schematic

Based on the work performed in the first semester of the project, design work hasbeen completed for the water production system. Individual steps of the treatmentprocess have been evaluated and optimized for best performance. Pretreatment,solids handling, the membrane bioreactor (MBR), reverse osmosis membranes (RO)

and post-treatment steps have each been assessed by a group member andcalculations checked by another. Specific plans, flow and head loss calculations andpricing have been assembled and are contained as well.

The collection and distribution systems are designed for the Red Mesas master planphases 1, 2, 3 and 4. Phase 5 of their plan has been omitted because of overlapconflicts with the property limits of RCS. The collection and distribution systems arealso designed for RCS based on their future expansion plans.

The collection system is entirely gravity fed save one location on the RCSs property.At this collection location, the wastewater is pumped through an 8 inch force mainback to another gravity fed section.

Watershed delineation was also done for the property. This resulted in Zones 1-4 asshown in Figure 3. Zones 1, 3 and 4 were found adequate in handling their stormwater runoff thus needing no improvement for drainage. Zone 2, however, with itsimmense size and rainfall volume, is a current concern and is made worse underdeveloped conditions. A storm sewer culvert has been designed in this area to

1Tao, G.H., K. Kekre, J.J. Qin, C.L. Ting, M.H. Oo, B. Viswanath, and H. Seah. MBR-RO for high-grade

water production from domestic used water. Water Practice and Technology. 1.2 (2006).

Distribution

InfluentWastewater

Pretreatment

Collection

MBR

RO

Solids Handling

EffluentDrinking Water

PostTreatment

Production Plant

Distribution

InfluentWastewater

Pretreatment

Collection

MBR

RO

Solids Handling

EffluentDrinking Water

PostTreatment


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Zone 1

Zone 2

Zone 3

Zone 4

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handle the flows resulting from rainfall. It will be left up to the contractor to design aprivate storm sewer to guide flows to this culvert.

Figure 3: Watershed Delineation with zones indicated

II. PERMITS/CURRENT SITUATION

2.1 Current Drinking Water SupplyThe Gallup basin lies within New Mexicos Water Planning Region 6 and is labeledas a high-desert environment. Of the 9 to 12 inches of annual rainfall, 97% is lostthrough evaporation or transpiration. Estimates are that only 1% of mean annualprecipitation recharges the local aquifers2. Desert/arid environments waters normallycontain high concentrations of dissolved minerals and salts (total dissolved solids).

2.1.1 City of Gallup Drinking Water SupplyThe City of Gallup pumps groundwater from the Gallup Sandstone and Dakota-Westwater aquifers to supply local water demands. The aquifers are deep and staticwater levels in the wells have declined several hundred feet in the past 30 years.There are 17 active wells that reach between 1500 and 2000 ft deep. Gallups

existing wells do not exceed EPAs total dissolved solids (TDS) standards and wellwater is only treated with chlorine.

In the Gallup region, most groundwater exists in confined sandstone and limestoneaquifers with low storage coefficients, resulting in large and widespread welldrawdown. Depth, quality, and formation productivity are the major physicalconstraints on groundwater availability in the area. Areas outside the Gallup

2Gallup Town Hall Summary, 2004

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Sandstone and Dakota-Westwater aquifers have groundwater but water depths areoften too great, water-bearing materials may be impermeable, and poor water qualityprohibits use. Many of the aquifers north and east of Gallup (the Rehoboth site) arehigh in total dissolved solids (TDS greater than 1000 mg/L) and exceed secondarydrinking water quality standards.

If water demand patterns continue following the trend of increased use, the city ofGallup will be facing water shortages during peak demand months as early as theyear 2010. All groundwater within the Gallup area is already appropriated. There ismore recoverable water in various locations but required well spacing, drawdown,and well recovery time make new water developments in the area impractical. Thisis the reason for the water production program being implemented within the nextdecade through use of membranes and RO filters.

There is hope for the future that a joint Navajo-Gallup 130 mile pipeline will be built tobring in water to the area from the San Juan River. Several years ago the nativeNavajo people were successfully awarded water rights on the San Juan River. Thepipeline would begin west of Farmington, NM at a point on the San Juan River and

move southward through the eastern reaches of the Navajo Reservation to theNavajo Capital at Window Rock and to the City of Gallup and its neighboring NavajoChapters. However, the pipeline will not be completed in the near future. Fundingfor this 0.5 billion dollar project needs to be obtained at both the state and federallevel before it is completed. This pipeline would likely supply the regions waterneeds for the next forty years. One trusted local contact stated that he did not thinkhe would see the results of this project for 20 to 25 years.

Aquifer storage and reuse has also been evaluated in the Gallup area. It was madeknown by Lance Allgood that this is not a viable option due to the characteristics ofthe local aquifers. In the conclusion of one Gallup water report, it was stated that nolong term groundwater solution is possible for Gallup and a surface water supply

needs to be sought, such as the Navajo pipeline.

2.1.2 RRMF Drinking Water SupplyThe RRMFs lands sit on the San Andres-Glorieta aquifer. There are no wells onthe RRMF site and no distribution system. A new water distribution system andpossibly a drinking water treatment plant onsite will be needed to treat and distributethe foundations future water needs. Gallup has a policy that they will not supplydrinking water to any development outside of city limits. Phase 1 of the foundationsdevelopment will fall within city limits and the foundation expects to have Gallupsupply this area with water. Phases 2-5 fall outside of the Gallups city limits. Afterspeaking with Lance Allgood, it is unclear if Gallup will supply the future needs ofPhases 2-5. Lance stressed that the foundation would have to offer something of

value to Gallup for use of its water resources. This would mostly likely be in the formof money as the RRMF has no water rights to forfeit.

2.1.3 Rehoboth Christian School Drinking Water SupplyThe school currently manages its own drinking water supply, chlorinatinggroundwater from the San Andres-Glorieta aquifer. Water from the Glorieta aquiferhas proven to be good quality and is only treated with chlorine. The school uses 20

AFA annually, with about 10 AFA coming from two wells. Well #00894 pumps 30GPM or 48.39 AFA at 528 ft of depth and well #00895 pumps 20.1 GPM or 32.26


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AFA at 481 ft of depth3. Both wells drawing at maximum capacity can produce72,144 GPD, roughly an eighth of future water needs for both developments.Thirteen more wells drawing at 30 GPM would be needed to meet the demands ofthe new developments.

Other water exists much closer to the surface of Rehoboth but it is of poor quality.

The poor water quality is due to overlying low permeability zones within the ChinleFormation which acts as a confining unit for the San Andres-Gloireta Aquifer. Thesezones have high levels of TDS, over 1000 mg/L.

After speaking with Mike Johnson, Bureau Chief of the New Mexico HydrologyBureau, it was learned that there is insufficient data to evaluate long-term water leveltrends in the region or the possible level of production from the Glorieta aquifer.

After speaking with Jason Zylstra, it was realized that the school is not utilizing anartesian well onsite. This well naturally produces 9,000 to 12,000 GPD of water thatflow into a nearby pond, where the water evaporates. Very high salt content andsubsequent fatal irrigation has prevented RCS from utilizing this well. The school isconsidering treating this well with RO membranes and using it for drinking water.

An expanded water distribution system and a water production facility onsite areneeded to distribute and treat the schools future water needs. A water productionfacility is necessary because the current production of the schools two wells onlypartially meets the future needs of both developments.

2.2 Groundwater RightsAs a member of the Colorado River Compact, Gallup is part of the most complexwater appropriation systems in the United States. New Mexico, like many Westernstates, uses the Doctrine of Prior Appropriation when determining water law andwater rights administration. This doctrine contains two essential principles: 1) thefirst user (appropriator) of the water has the right to continue to use it, and 2) the

right to that water continues as long as the appropriator puts the water to beneficialreuse. The use of the water begins when the water is first diverted from a surfacewater body or pumped from the ground. In New Mexico, the person with the oldestwater right is entitled to his full amount. When he is finished, the next person isallocated his amount and so on until the supply is exhausted. Water rights understate law can be bought and sold.

To obtain more water appropriations the school and foundation will need to apply fora water appropriation permit. This application process is required for all newdevelopments. The Office of the state engineer in Albuquerque, NM will then cometo the site and perform a total water quantity study in that area. The state engineeralso measures the effect any new water mining will have on nearby water users. All

appropriations are performed and awarded on a case-by-case basis. Since theremay be no available water appropriations in the Rehoboth area, Rehoboth may haveto buy appropriations from neighbors to use the groundwater sources beneath them.If there is available water to appropriate, the school and foundation must post adeclaration in the paper. If anyone protests this declaration, fearing that their seniorwater rites will be jeopardized by new water mining in the area, the case goes tocourt in Santa Fe, NM. Only after several years of litigation will a judge reach a

3Drinking Water Bureau under the New Mexico Environment Department


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solution. To quote Dan McGlaughlin, a civil engineer who has done consulting workin the region for many years, Determining water rights in New Mexico involves half adozen lawyers and a judge consulting the entrails of a sheep.

2.2.1 Gallups Water RightsGallup is currently using half of the 8,600 AFA (acre-feet/year) water appropriations

they are permitted for. Using half does not mean there is more available water.Water appropriations could have been awarded before adequate studies of theaquifer were performed. It will be the responsibility of Gallup to determine if they areable or willing to supply Rehoboths developments with drinking water.

2.2.2 RRMF Water RightsThe RRMF has no groundwater rights or prior appropriations. To obtain more water,the foundation will need to apply for a water appropriation permit or buy drinkingwater from Gallup or the RCS.

2.2.3 Rehoboth Christian School Water RightsThe school is currently appropriated for a total of 80.65 AFA. This volume may meetthe future needs of the schools developments, but not the RRMF. If they need morewater for their developments, the school will need to apply for a water appropriationpermit or purchase water from Gallup.

III. SITE

3.1 Rehoboth Red Mesa Foundation Development PlanThe RRMF East Gallup Property constitutes 800 acres. Of those, 772 acres are inMcKinley County and 28 acres fall within the city of Gallup along its eastern edge.The foundations lands are primarily south of Interstate 40 and wrap around the

Rehoboth School property and continue westward to the eastern edge of Gallup.There are no existing structures on the RRMF lands. The planned RRMFdevelopments can be viewed in Figure 4 and are divided into five phases: EastGallup Neighborhood Center (1), East Gallup Regional Center (3) and MedicalDistrict (4), West Village Residential Community (2), and the East Village ResidentialCommunity (5).

3.1.1 East Gallup Neighborhood CenterThe East Gallup Neighborhood Center (Phase 1) is a 7.5 acre parcel of land locatedalong the eastern edge of Gallup and southern edge of I-40. The NeighborhoodCenter is designed to contain a variety of businesses: a grocery store, deli, bakery,hardware store, pharmacy, coffee shop, and video store. Buildings in this phase are

planned to be 1-2 stories tall with apartments on the second floor. TheNeighborhood Center will rely on Gallups water and sewer. The RRMF has plans toallow Phase 1 to be annexed by the city of Gallup, thereby passing liability for waterdelivery and treatment to Gallup.

3.1.2 East Gallup Regional CenterThe East Gallup Regional Center (Phase 3) is a 70 acre site located east of theNeighborhood Center (Phase 1). The purpose of the Regional Center is to providefor the daily needs of workers, residents, and visitors in the area. Businesses may


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include restaurants and cafes, pharmacies, day care, dry cleaners, video stores,hardware stores, travelers services, and other related businesses. A portion of thisarea may be designated for light industrial use such as warehousing. The RegionalCenter will include an extensive housing development of 200 lots that mirrors andexpands the type of housing found in the residential communities (Phases 2 and 5).

Figure 4: RRMF development plan

3.1.3 Medical District

The Medical District (Phase 4), a 60 acre site, is designated for one or two regionalhospitals: the Rehoboth McKinley Christina Health Care Center and the GallupIndian Medical Center. Though it is still uncertain whether these hospitals will bebuilt, Team 10s design includes the flows required by these two hospitals.

3.1.4 West Residential CommunityThe West Village Residential Community (Phase 2) will be a located south of theMedical and Regional Centers. The West Village is comprised of 80 single familylots ranging from 1/3 to 1/6 acre in size.

3.1.5 East Residential CommunityThe East Village Residential Community (Phase 5), located southeast of the RCS,

will have 120 single family housing lots. With its distance from the city of Gallup, thisphase is scheduled to be completed last.


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3.2 Rehoboth Christian School Development PlanThe RCSs developments are broken into four phases with a large area set aside forfuture phase developments (Figure 5).

Figure 5: Rehoboth Christian School Development plan

3.2.1 Residential Phases

All four phases are planned for residentialdevelopment. Phase 1 is the existingresidential community. There are about100 residents occupying 30 homes inPhase 1. During the school year thedaytime population on the school landsincreases to 500 people. In the future, theschool hopes to increase its daytimepopulation to 700. Table 1 summarizesthe number of lots in each phase.

3.3 Site Design Considerations

The school and the foundations site plans were used to calculate future wastewaterflows and drinking water needs of the developments. Team Oasiss watermanagement design is conservatively based on the wastewater and drinking waterneeds of these future developments if they were entirely built as planned. TeamOasis understands that it may be many years until these developments are finishedbut needed to choose a solution that would encompass the entire needs of Rehobothand would properly plan for the future.

Table 1: School Lot AppropriationsLots

Phase 1 (Existing) 30Phase 2 28Phase 3 21Phase 4 46

Future Phases 74Total Lots in Planned Phases 125

Total Lots 199

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IV. SANITARY COLLECTION

4.1 Overall DescriptionThe sanitary sewer is a gravity fed system that flows to a selected low point withinthe construction boundaries. This location corresponds to the location of thewastewater treatment plant, which is just west of RCSs property and borders theeastern edge of the RRMFs Phase 4. At one location in the schools property, aforce main is required to handle the wastewater due to a steep elevation change.

4.2 Sanitary SystemA Sanitary Design program in Microsoft Excel provided by Professor Hoeksema wasused to design the piping network. The program requests the per capita flow rate,number of homes, and average number of people per home. From these inputs, atotal flow is calculated which is then multiplied by a peaking factor to account forspikes in flow during the day. The user sets the length of pipe in the system for eachsection along with a drop of 0.1 feet for each manhole. Infiltration is also accountedfor with the program. This component is estimated as 5000 gallons per day, per mileof pipe. The program then distributes the total flow of sewage to every pipe in thesystem to simulate houses feeding into the system. The program calculates resultsfor flows, slopes, pipe diameters, and pipe inverts. Each pipe is sized and thenevaluated in order to avoid pressurized flow in the gravity fed system.

Our design consists of construction plans that lay out and detail the pipe locations,sizes, and inverts. This was accomplished through an overall site plan andcorresponding pipe profile views.

Each pipe is laid at either a minimum cover of 10 feet or at a minimum slope. Theminimum cover of ten feet is the first criteria. This requirement is in place so thatwhen the pipe is laid it will be below the foundation and basement of any existing orfuture houses and also below the freeze level. This also allows for lateral pipes fromeach building to slope down toward the sanitary sewer main line in the street.

The second requirement of minimum slope is designed based on the size of the pipe.This requirement is in place to provide a flushing velocity of 2.0 feet per second,which helps prevent settling and deposition of the wastewater solids. See Appendix

A for the minimum pipe slopes for different diameter pipes.

A lift station is used to handle the wastewater for the development plans of theschool. An 8 sanitary force main carries the wastewater from the lift station to amanhole about 44 above the lowest invert into the lift station. The forcemain is876.9 feet long. The pump is designed to handle the flows of the sanitary sewer.The maximum flow rate of this pump is 0.322 cfs and the minimum flow is 0.073 cfs.

The minimum inflow is 0.072 cfs, so the lift station will never be unable to handle theinflows. The wastewater network is then gravity fed to the treatment plant.


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4.3 Sanitary CostingThe cost of the sanitary sewer pipe is based on pipe size, trenching, sand fill andcompaction. The estimate for the cost was obtained from RS Means ConstructionCost Data.4 See costing data, Table 2.

Table 2: Sanitary Sewer Cost Summary

Sanitary Sewer CostCOST Price/10' Length Length/10 Price

8 13.6 27489 2748.9 $37,385.04

10 20.5 1926 192.6 $3,948.30

12 23 1811 181.1 $4,165.30

15 35.5 1907 190.7 $6,769.85

18 29 639 63.9 $1,853.10

21 36.5 1664 166.4 $6,073.60

Total $60,195.19

Manholes

Price Total Cost

Manholes 147 $2,625.00 $385,875.00

Trenching CY of soil

Excavation 425232 2.93 $1,245,929.76

Sand 70872 12.75 $903,618.00

Compaction 70872 3.95 $279,944.40

assumed 6' wide and 18'deep with a 3 yd

3bucket

assume 6' wide and 3' deep of

sand for length of all pipe

Lift Station

Cost Total

Sewer Lift Station 1 Ea $76,500.00 $76,500.00

Total $2,952,062.35

4.4 Codes/Standards for Sanitary Sewer

Codes and standards were followed for the design of the sanitary sewer. The

sanitary sewer system meets the minimum required standards as shown in Title 17Chapter 13 Part 950 of the New Mexico Administrative Code.See Appendix A: Minimum Standards for Design, Construction, and Operation ofSewer Utilities.

4 RSMeans.Reed Construction Data: Building Construction Cost Data. Massachusetts: Construction Publishers andConsultants. 2007


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V. BASIS OF WATER PRODUCTION DESIGN

5.1 Water Production FacilityDue to water shortages in the Gallup/Rehoboth region, a water production facility hasbeen proposed for the school and the foundations planned developments. Thecurrent aquifer productivity of the school will not meet the predicted water needs fordevelopments of this size. A study of the current water rights situation found that anyfuture pipelines into the area yield little hope for water sources in the near future.The basic needs are outlined in Table 3.

Table 3: Average Daily Flow (ADF) Summary

Region Sanitary Flow Generation (ADF) Drinking Water Need (ADF)

Phase 1 8,082.00 7,347.00

Phase 2 15,682.00 18,725.00

Phase 3 61,429.00 65,180.00

Phase 4 33,248.00 30,225.00

Phase 5 23,522.00 28,088.00

Rehoboth School 59,226.00 64,961.00

TOTAL FLOW = 201,189.00 214,526.00

Therefore, a water production facility has been proposed by Team Desert Oasis thatwill recycle approximately 70% of all wastewater used by Rehoboth.

In the fall of 2006, Team 10 proposed a membrane bioreactor water productionfacility as a safe and effective solution to reuse much of the water that wouldotherwise be treated and wasted to rivers and lakes. This unconventional MBRproduction plant was chosen because it provides the cleanest effluent water of anymunicipal treatment method. Employing this toilet to tap plant design will eliminate

Rehoboths dependency on the City of Gallup for drinking water and wastewatertreatment.

A membrane bioreactor (MBR) is the primary source of treatment for the influentwastewater. Reverse osmosis (RO) membranes will then act as a secondarytreatment to further improve the quality of the drinking water exiting the plant. Toensure the utmost safety, as the water will be pumped directly into the distributionline with no buffer time, ultraviolet (UV) disinfection will be attached to the effluentRO stream. Finally, to combat bacterial growth within the distribution network, aSodium Hypochlorite (residual chlorine) drip feed is connected to the stream as itexits the plant.

5.2 Flow InformationThe flows coming into the plant were estimated using accepted EPA guidelines forthe different kinds of establishments being planned for construction in the phases ofdevelopment. Other flows within the production plant were found using informationspecific to the piece of equipment chosen in the design. A flow summary follows inTable 4.

There are two key sections of the plant which require water being supplemented by athird party source (other than the influent wastewater). The first section is in theSolids Treatment portion, and the second section is under the 25% flow lost to RO


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section of the above table. The recommended source of the water required tomakeup for these losses is from the aquifers nearby. This could include the aquiferwhich is currently being employed by the school to meet todays demand as well asanother, more distant aquifer. Another engineer would need to design the intake,and pump required for this operation to make it connect into the treatment plant in-line with the rest of the treated water. If the supplemented water is of good enough

quality, it could be fed directly after the RO membranes for disinfection treatmentonly.

Table 4: Water Production Plant Flows

Flow Liquid Treatment [MBR]

ADF 201,188 gpd

MDF 402,376 gpd

Flow Solids Treatment

ADF 3,643 gpd

MDF 7,286 gpd

Flow Liquid Treatment [RO]

ADF 197,545 gpd

MDF 395,090 gpd

Flow - 25% Lost to RO

ADF 49,386 gpd

MDF 98,772 gpd

Potable Water Exiting Plant

ADF 148,159 gpd

MDF 296,317 gpd

Amount of Water that Will Need to be Supplemented by Schools Wells

ADF 66,367 gpd

MDF 132,734 gpd

5.3 Equipment ChosenSeveral pieces of equipment were designed to meet the needs of each step in theproduction process. Contacts were made with representatives from each of themanufacturers (Appendix C) of the appropriate equipment, and information as wellas cost estimates were obtained. A table summarizing the model numbers andcapacities of each piece of equipment chosen is shown in Table 5.


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Table 5: Water Production Equipment

MAKE MODEL/DESCRIPTION CAPACITY UNITS

Lifting Station

Dakota Pump420 GPM/50'TDH,1800RPM Vertical Built

together 402,000 gpd

Pretreatment

Waste-Tech RotoSieve Screen Model 4024-40, 2mm-screen 400,000 gpd

Screenings Compaction KP200 Piston Press 400,000 gpd

Grit Classifier Model WTI/CONPURA SD320 460,800 gpd

Membrane BioreactorGEWater/Zenon Z-MOD Type L Packaged Plant 672,000 gpd

Solids Handling

Huber Tech Rotomat Rotary Screw Thickener 504,000 gpd

Vogelsang V100-45Q HD 99,360 gpd

Vaughan SP4C Model 216,000 gpd

Alfa Laval 750K Spiral Heat Exchanger 288,000 gpd

Thermophilic Digester 4,370 gal

Reverse Osmosis

GE Water Model 1225595, RO PRO-150-PRE 300,000 gpd

Ultra Violet

Wedeco ITT UV Unit Type B 160 DVGW/ONORM 600,000 gpd

Chlorination

Cole Parmer Peristaltic Pumps 22.80 gpd

VI. LIFT STATION

6.1 IntroductionBecause the elevation of the sanitary sewer lines entering the plant is about 23 feetbelow grade, a lifting station is needed to pull the head above the surface elevation.

The goal is to be able to gravity feed the water through a portion of the plant tominimize the work needed to be done by any of the pumps within the treatment plant.


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Figure 6: Elevation view of Lift station

6.2 Lift StationThe company chosen to design the lifting station came highly recommended by localconsulting company, Prein & Newhof. The specific model quoted is the 420 gpm, 50ft TDH (total displacement head), 1800 RPM Vertical Builtogether. This amount offlow carries the ability to meet and exceed the capacities that the plant will be dealingwith during maximum flow conditions. The amount of head provided is also morethan enough to maintain good pressure into the plant.

VII. PRETREATMENT

7.1 IntroductionZenons membranes are designed with pore openings of less than 0.1 microns andcan easily be damaged or fouled by trash and non-biodegradable solids such as hair,lint, grit, and plastics. To enhance the long-term operation and effectiveness of theMBR plant, Zenon recommends redundant internally-fed screens with mesh orpunched hole openings less than or equal to 2mm.

After researching different pretreatment options and receiving quotes from several

companies, Waste-Tech, was selected to furnish the plants pretreatment needs.Waste-Techs Roto-Sieve Drum Screen was selected as the best screen for ourfacility. The Roto-Sieve Drum Screen was recommended by a sales representativeat Zenon and was chosen for its modular design, proven performance in the field,2mm screening capabilities, and reduced capital, operation, and maintenance costs.See Figure 7 for a pretreatment flow diagram.

7.2 Roto-Sieve Drum ScreenThe RotoSieve Model 4024-40 consists of a rotating 2mm perforated drum with aninternally mounted transport screw which transports the separated solids from the


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drum. The drum rotates on trunnion wheels and is operated by a cog gear motor.The incoming water is fed into the drum by means of an inlet pipe which distributesthe water over a large area of the drums inside. The drum screens are completelyencased with detachable splash guards and have been equipped with an overflowsystem.

Two screens will be installed and each has the capacity to screen average flows of0.2mgd and maximum daily flows of 0.4mgd. The screen operates properly at totalsuspended solid levels of up to 250-300mg/l.

Figure 7: Pretreatment Schematic

[See Appendix C for Equipment Manufacturer Specifications]

7.3 Screenings CompactorEach screen is equipped with a KP200 Screenings Compactor. This devicedewaters, compacts, and transports the screenings to a nearby dumpster.Screenings are fed into an outer cylinder in which an axially elongate piston isarranged. The piston uses reciprocating motion to force the refuse towards the outletof the cylinder. The cylinder has apertures for allowing water to escape from the wetrefuse as it is compacted against a conically shaped member at the outlet of thecylinder. Compacted screenings will be transported to a nearby landfill. The volumeof compacted screenings produced daily is dependent upon the quantity of rags andfloatables in the future influent wastewater. [See Appendix C for EquipmentManufacturer Specifications]

7.4 Grit ClassifierThe SD320 Grit Classifier is comprised of a hopper with an inlet pipe, an internal weirand outlet pipes and drain down valve, and an inclined trough with an ArchimedeanScrew arrangement driven by an electronic motor and gearbox. The mixture of gritand effluent water from the screens are fed directly into the grit classifier through theinlet box and diverted into the trough. The grit is deposited on the bottom of thetrough and transported up the inclined Archimedean screw and discharged at highlevel through the grit outlet to a dumpster below. The pretreated water then drains to


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an outlet trough and into the plant. [See Appendix C for Equipment ManufacturerSpecifications]

VIII. MEMBRANE BIO-REACTOR

8.1 IntroductionSeveral key factors led to the decision that a membrane packaged plant should bechosen over a specifically designed conventional water treatment plant. The plug-and-play membrane ultrafiltration (UF) systems outperform conventional treatmentalternatives in all categories, offering reduced operating costs, smaller plantfootprints, more reliable performance, and high quality effluent that meets or exceedsthe worlds most stringent discharge and reuse standards. Membrane plants arecurrently the best tested and proven method for municipalities to transform largeamounts of wastewater to drinking water quality.

8.2 Membrane Bio-Reactor

Though a specific quote was not obtained from GE, a budgetary proposal (AppendixC) to the Village of Ostrander, OH, was found to be nearly identical to the flows andloads present in the Rehoboth design. The Village of Ostrander project consisted ofa plug and play Zenon Z-MOD L96D prepackaged membrane design that treats anaverage daily flow (ADF) of 180,000 gpd and can support a maximum daily flow(MDF) of 360,000 gpd for periods not exceeding 24 continuous hours. Though theflows in the Rehoboth plant are slightly larger than those in Ostrander, the capacityof the L96D model easily meets these higher flow rates. An orthographic view of theZ-MOD-L configuration is shown in Figure 8.

Figure 8: Z-MOD L Basic Layout

The contaminant removal of the Zenon model is impressive. In the budgetaryproposal provided to the Village of Ostrander a table (Table 6) outlines thecontaminant removal estimates.


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Table 6: Zenon Model Removal Estimates

With comparable contaminant levels found in Rehoboth, a similar removal could be

expected, according to conversations with a Regional Sales Manager at GE, DanHiggins.

8.3 Effluent QualityIn meeting the standards of the New Mexico Environmental Department, certainqualities of the contaminants must be obtained. The quality of water coming out ofthe membrane bioreactor is represented in Table 7.

Table 7: MBR Effluent Quality

Contaminant Concentration

TSS 5 mg/L

Turbidity 1 NTUNitrates 1 mg/L

E Coli 2.2 CFU/100 mL

IX. REVERSE-OSMOSIS MEMBRANES

9.1 IntroductionThough the quality of effluent coming out of the MBR is within the standards ofdrinking water quality, an extra membrane step is installed to ensure that the qualityof effluent water is safe for consumption. Reverse osmosis (RO) was chosen as themethod of treatment to accomplish this polishing step. As MBR technology is

primarily used in wastewater treatment, RO is used almost exclusively in treatingdrinking water.

9.2 RO MembranesAfter making the decision to select Zenon as our MBR manufacturer, it becameevident that it would be advantageous to purchase a corresponding Reverse-Osmosis (RO) packaged plant from the same manufacturer. In talking to contactsrepresenting the two most important steps of the treatment process (MBR and RO), itwas clear that having contacts with the fore-knowledge of both types of equipment


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was an advantage. General Electric owns Zenon as well as GE Osmonicsa largedivision of the company which specializes in drinking water treatment equipment.

After talking with both representatives from both Zenon and GE Osmonics, the modelchosen was the PRO 150 RO packaged unit. A profile view of this packaged unit ispictured in Figure 9. To provide for redundancy, two of these packaged units will bepurchased. Each unit will have the capacity to handle maximum flows of the plant.

Figure 9: GE Osmonics PRO 150

One aspect of reverse osmosis which must be addressed is the loss of water due tothe screening out of rejected water. This loss is estimated to be 25%, about 50,000gal/day during average daily flow (ADF) and 100,000 gal/day under maximum dailyflow (MDF). To make up for this loss, water will have to be supplemented from aneighboring aquifer (likely the Glorieta) at a rate of 66,000 gal/day ADF and 132,000gal/day MDF.

9.3 Waste StreamWith an estimated loss of 25% coming out of the RO, a destination must be found forthis concentrate water. One option considered for the RO concentrate stream wasan evaporation basin. This design was based on evapotranspiration rates from theGallup-New Mexico region. To evaporate the concentrate wastewater for bothaverage flow conditions a basin size of 11 acres was needed. For maximum flowconditions 22 acres was needed. This area proved to be too large for the basin to beconsidered as a feasible solution for the concentrate stream. There was simply notenough land to accommodate an evaporation basin of this size between the twofuture developments. Gallup also has an extended winter season due to its higherelevation that must be considered. An evaporation basin would not perform well for

6 months of the year.

After more research and speaking with those knowledgeable in this field, TeamDesert Oasis recommends a soil-aquifer recharge system as a future solution. Asoil-aquifer system would allow wastewater to leach through permeable sand intounderlying aquifers, recharging groundwater. This design has been considered outof scope for this project.


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X. POSTTREATMENT

10.1 IntroductionThough the drinking water exiting the reverse osmosis membranes is of drinkingwater quality, it is imperative to make sure that any remaining bacteria or microbeswill not enter distribution. Disinfection is the main tool with which to ensure that this

is the case. With this project, it was decided to use two separate forms ofdisinfection to ensure both aspects of disinfection are addressed: eradication ofmicrobes, and a residual chemical to prevent microbial life from springing up duringdistribution. Ultraviolet (UV) treatment was chosen as the primary disinfectionmeasure as it is an inexpensive, reliable method of treatment and creates no harmfuldisinfection by-products (DBPs). The second disinfection measure will be the use ofa chlorine carrier called Sodium Hypochlorite.

10.2 Ultraviolet TreatmentThree UV treatment companies were contacted to provide some options from whichto make a decision. The decision was primarily made based on the ability of thecompany to provide equipment relevant to this project. Because the flows of this

design are relatively small, only one company, Wedeco ITT, was found to be able toprovide the correct equipment.

Figure 10: Ultraviolet Treatment Schematic

The model recommended per a quote from Wedeco (Appendix C) given on March

26, 2007 is the Wedeco UV Unit Type B 160 DVGW/ONORM (Figure 10). Becausethe bulbs have an extremely high output (300 J/m2) and an estimated UVtransmittance of 98% per 1 cm, only 4 bulbs are needed for the relatively highvolumetric flow rate. The dimensions (1.3 x 0.5 x 0.33 m) of the unit are such that itcan be placed directly inline with the permeate stream from the RO unit.

To allow for the ability to change the bulbs without interrupting flow, two units will bepurchased. The very low power requirement associated with UV units makes thepower cost very minimal.


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10.3 Sodium Hypochlorite AdditionSince the UV units have removed all of the microbes alive in the effluent from thereverse osmosis membranes, the addition of a disinfection chemical is used toensure a residual chemical is available to stifle microbe growth throughoutdistribution. Because the primary function of this step is to act as a residual, themost trusted disinfection chemical which creates the fewest amounts of disinfection

by-products was selected, Sodium Hypochlorite.

According to calculations performed in MathCAD (Appendix B), a feed rate of 8.8mL/min 24 hours a day is required from 12.5% Sodium Hypochlorite liquid. Thischemical is commonly purchased in 55-gal containers from any number of chemicalproviders and was sized to be applied with simple, peristaltic pumps from Cole-Parmer at a relatively inexpensive cost.

XI. SOLIDS HANDLING

11.1 IntroductionThe solids handling system within the treatment plant consists of a rotary drumthickening unit, recirculation pump, spiral heat exchanger and thermophilic anaerobicdigester. Ultimately after stabilization in the digester, the solids will be transportedand used as Class B land application solids.

11.2 ThickeningAs the waste stream leaves the MBR, solids make up 1.2% of the volumetric flow. Atthis concentration a digester volume of more than 18,000 gallons would have beenrequired. If a thickening method were added to increase the solids percentage to5%, the volume required decreases to 4,372 gallons. Along with a reduction inconstruction costs, thickening recycles more water back to the beginning of the plantand with New Mexicos current and future water shortages, conservation madethickening the most viable option. The 5% solids concentration was selectedspecifically for the land application of the solids. Class B solids requirements dictatethat treated waste cannot be distributed above ground, but must be injected into theearth. Higher concentrations of solids would make this injection difficult. Two basicmethods were considered: centrifuges or a rotary drum. Centrifuges can reducewater content up to a 60% solids concentration; a concentration far greater thanrequired for this plant. Rotary drum technology was more flexible and conducive tothe very small capacity of our plant. For the final design the Rotamat Rotary ScrewThickener [RoS2] from Huber Technology was selected; the smallest size they offer.This unit is still operational under our minimal flow and thickens to range of 4-8%solids. [See Appendix C for Equipment Manufacturer Specifications]

11.3 RecirculationTo ensure that the anaerobic process is continuously functioning, the stabilizingsludge must circulate. An averagely accepted value is a turn-around time of thirtyminutes, or the complete circulation of the contents in the digester within a half-hour.Vaughan was contacted about a possible Rotamix system. The plant size,however, made the complete system unnecessary and it was decided to only useand integrate the SP4C-4CSB self-priming Vaughan pump with all informationprovided by the distributor, JGM Valve Inc. This chopper pump is able to move a


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stream of 5% solids at 150GPM, against 12m of head through the system.[Calculations in Appendix B and Manufacturer Specifications in Appendix C]

11.4 HeatingDue to the thermophilic nature of the digester, a consistent temperature must bemaintained. This will be achieved through the use of a spiral heat exchanger

manufactured by Alfa Laval [model 750K]. This unit can deliver the energy neededto heat to the sludge as it moves through at the recirculation velocity of 150GPM.The manufacturer has designed the unit to be easily cleaned and easily accessibleduring maintenance procedures. The energy used to heat the water functioning asthe heating fluid begins in the digester as methane gas produced as the microbesperform their metabolic functions. This digester gas is cleaned to create a betterquality methane gas which will then be used to power a generator that can producesome electricity for within the plant. The heat from the generator will then be used toheat the water for heat transfer within the heat exchanger. [Calculations in AppendixB and Manufacturer Specifications in Appendix C]

11.5 DigestionAfter careful economic analysis, it was determined that a thermophilic anaerobicdigester would be more cost effective than a mesophilic digester. A heat exchangeras previously explain will be used to consistently keep the temperature within thedigester at 55C, creating the ideal environment for the microbes to actively stabilizethe waste. After the rotary drum thickener, the required volume is reduced to 4372gallons, and in choosing a cylindrical digester with equivalent height and diameter,the final height of the digester is 108 inches [9 ft]. The digester will be made ofreinforced concrete with 6 inch thick walls and a 1 foot thick bottom slab.[Calculations in Appendix B]

11.6 Sludge PumpsIn order to move the sludge from the thickener into the digestion system, and alsofrom the digesters into the storage silos, sludge pumps were needed. TheVogelsang lobe pump [V100-45Q HD] was highly recommended by Jeff Bramlage atKennedy Industries, Inc, the pump distributor. The positive displacement, rotary lobetype pump utilizes two HiFlo tri-lobe rotors to move sludge consisting of up to 10%solids. [Calculations in Appendix B and Manufacturer Specifications in Appendix C]

11.7 Waste RemovalAfter stabilization within the digester is completed, taking about 5 days, the sludgewill be pumped into a storage silo and stored for up to 4 months. Because there isyet not enough development within Rehoboth to use the solids, they will betransported to Gallup for use in their land application process. The anaerobicdigestion process is considered an acceptable PSRP [Process to SignificantlyReduce Pathogens] within the EPAs 40 CFR Part 503 Appendix B5, and our digesterachieves the required 38% VSS reduction under Class B biosolids provisions (EPAPathogen Reduction Requirements) with a 50% reduction (see digester calculationsin Appendix B). Gallup employs below-surface injection of solids, which whencombined with the minimum 38% VSS reduction, greatly reduces vector attraction.Vectors include flies, mosquitoes, fleas, rodents and birds that function as hosts for

5United States, Environmental Protection Agency [EPA]. Code of Federal Regulations (CFR) Title 40:

Protection of Environment. Washington: GPO, 1995.


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the transmission of diseases to humans. The VSS reduction significantly reducesthe number of pathogens the biosolids contain, while injection prevents vectorinteraction two-fold. First, injection provides an earthen barrier, preventing airtransfer of pathogens. Second, the soil removes water from the biosolids reducingthe possible mobility of pathogens and removing odor that would attract vectors.

XII. OVERALL WATER PRODUCTION COSTS

12.1 IntroductionGoing into the design for this project, a basic estimate was made for the waterproduction plant cost. The estimate was found based on conventional treatmentmethods as a matter of reference. The figure of $6 million was found based uponthe EPA documents released in 1979, Estimating Water Treatment Costs vol.1 andEstimating Wastewater Treatment Costs vol.1. The costs estimated in thesedocuments were then adjusted to the National Average of 2007 dollars with theEngineering News Record (ENR) adjustment factor. The overall costs for the waterproduction plant are represented in Table 8.

Table 8: Overall Water Production Cost

Name Constructed Cost Operational Cost

Lift Station $120,000 $16,000

Pretreatment $300,000 $1,400

MBR $910,500 $9,700

Solids Handling $616,885 $23,000

RO $405,939 $5,600

UV $81,000 $1,668

Chlorination $8,400 $1,800

Plant Operators (2) -- $60,000Pumping Station $17,595 $8,593

Watermain $1,500,000 $20,000

Contingency (20%) $492,063 --

TOTAL COST = $2,952,382.80 $150,761

12.2Cost ComparisonThe above total includes each significant purchase required to make the waterproduction plant function properly. Costs for materials of the building were left out,as were insurance costs for the proposed plant operators. When the costs wereconverted to dollars/thousand gallons (a common industry metric), the amounts werecompetitive for the region when compared to Sante Fe, NM and the state ofColorado as shown in Table 9.


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Table 9: Cost Comparisons

Rehoboth, NM First Year Costs

$3,256,542.6400 $/yr

200,000.0000 gal/day

73,000,000.0000 gal/yr

$0.0446 $/gal$44.6102 $/thousand gal

Rehoboth, NM Operational Costs

$153,945.6400 $/yr

200,000.0000 gal/day

73,000,000.0000 gal/yr

$0.0021 $/gal

$2.1088 $/thousand gal

Sante Fe, NM Operational Costs


Colorado Water Resources Research Institute


As is shown in the table above, it is shown that the cost of producing water isapproximately half that of a major city inside of the same state, Sante Fe.

XIII. BIOGAS TREATMENT

13.1 General Comments

Presently, an air treatment process is beyond the scope of this project. In the future,the impurity of the collected digester gas would have to be considered and an air-stripping mechanism designed. A suggested design, by the janitor at the

Albuquerque wastewater treatment plant, included freezing the air to remove anyimpurities. Air purification is only necessary if the methane gas is being recycled andused to fuel a generator. The energy generated can be used to power parts of theplant, thereby cutting down on electrical costs, while the heat generated will used toheat water which will then flow through the spiral heat exchanger heating the sludgeto thermophilic temperatures.

XIV. ELECTRICAL AND INSTRUMENTATION

14.1 General CommentsThe instrumentation plans for the treatment process are beyond the scope of themanagement plan. Zenons proposal yields the following information about theprepackaged controls for the ZMOD-L unit:

A KOYO Programmable Logic Controller (PLC) with a HumanMachineInterface (HMI), installed in the main NEMA 12 controlpanel, monitors and manages all critical process operations.


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Level controls monitor the level of mixed liquor in the processtanks and transmit this information to the Z-MOD PLC. ThePLC will automatically adjust the flow of the ZMOD trains basedon proportional control to the process tank levels in order tominimize the instantaneous flux of the membranes. During aninfluent surge, the permeate pump will enable the system tohandle up to twice the ADF for a period not to exceed 24consecutive hours. In the event of a system or equipmentproblem requiring operator attention, the PLC can either alert theoperator or shut the system down. The control panel includes allmotor control hardware for the ZENON

Z-MOD Budgetary Proposal (Appendix C)

XV. PLANT BUILDINGS

15.1 General CommentsWhen constructing the actual building schematic for the water plant, it was evidentthat much of the schematic would be outside of the scope for an environmentaldesign. Things such as general dimensions of the two excess rooms were designedfor, as well as a plan to include floor drains in each section of the plant whichfunctions in the capacity of treatment. This would allow for the maintenance andreplacement of each significant portion of the plant. Specific drawings of theseportions of the plant were not included in the final printout, but would be designed bya mechanical systems engineer as well as an architect. These individuals wouldalso be in charge of creating plans for other structural elements of the plantstructural loading, plumbing for the bathroom, HV/AC throughout the plant, etc.

XVI. DRINKING WATER DISTRIBUTION

16.1 General CommentsThe water distribution network is placed at a minimum of 5 below grade to avoid thefrost line. The pipes will also be placed on the opposite side of the street to preventconflict with the sanitary sewer pipes.

The network is split into three different pressure districts due to large changes inelevation across the site. Pressure control valves and pumps are used to control thepressure for these districts. The pressures in the network are controlled by thesedevices to keep the pressure between 30-70 psi. The head in each district ismaintained by three water towers, one located in each pressure zone.

16.2 PipesCurrently, asbestos clay pipes are used to distribute water to the RCS. The newdrinking water distribution network utilizes ductile iron pipes, which provide thenetwork with extra strength and durability. The watermain system used includes 8and 12 diameter pipes.

16.3 PumpsTwo identical redundant pumps supply water to the drinking water distributionnetwork. These pumps were designed using a Cornell Pump program and selected


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based on advice from a Cornell representative, which finds a pump based on desiredpump head and flow values. Each pump is designed for 148.97 GPM and 275 feetof head at 3600 RPM. The pump that we selected is a 1.25Y with a 9.31 impeller.

A control is placed on one pump to regulate flow when certain water levels areachieved in the water towers. This assures that the water towers remain full. Energyis conserved because the pump will not have to run all the time.

Between the southwest district and the west district, an additional booster pump isneeded to obtain pressures that fit between the required maximum and minimumpressures. This pump is a 1.25W pump, which operates at 42.5 GPM, 42.5 feet ofhead at 1800 RPM with a 6.44 impeller. A by-pass pipe is also being utilized toprovide the necessary flow in the event of a fire in this district and redundancy incase of a breakdown. The pump shuts off and the pipe opens to provide for this highflow event.

16.4 Water TowersThree water towers are designed for the use in the drinking water distributionnetwork. The first water tower in the west district is at elevation 6603 with an initial

water level of 120. The second water tower in the south west district is at elevation6670 with an initial water level of 60. The third water tower in the east district is atan elevation of 6750 with an initial water level of 75. These water towers arenecessary to hold an appropriate head level and provide additional water flow tohandle the demands in case of a fire.

The cost and design of these water towers are outside the scope of our project.

16.5 CostingThe cost of the distribution network is based on the size of the pipe, the pumps,trenching, sand fill, and compaction. The estimate for the cost was obtained from RSMeans Construction Cost Data. The pumps pricing is based on a quote from CornellPump Company. See costing data, Table 10.

16.6 Codes/Standards for WatermainCodes and standards were followed for the design of the water main. All thewatermain pipes meet Title 17 Chapter 12 Part 750 of the New Mexico

Administrative Code that has minimum standards for design of water utilities. SeeAppendix A: Minimum Standards for Design, Construction, and Operation of WaterUtilities.


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Table 10: Watermain Costing Data

PIPE TOTALS

8" Pipe 6549.5 LF

12" Pipe 35661.4 LF

Price Amnt. Total8" DI Pipe 6550 LF $28.50 363.89 $10,370.83

12" DI Pipe 35662 LF $41.00 1981.22 $81,230.11

12" PRV 8 Ea $4,000.00 $32,000.00

12" Valve and Box 90 Ea $1,950.00 $175,500.00

8" Valve and Box 16 Ea $1,175.00 $18,800.00

8x12 Tee 13 Ea $453.00 $5,889.00

12x12 Tee 23 Ea $1,700.00 $39,100.00

8x8 Cross 1 Ea $600.00 $600.00

12" 90o

Bend 4 Ea $785.00 $3,140.00

Fire Hydrants 141 Ea $1,775.00 $250,275.00

12x6 Tee 119 Ea $393.00 $46,767.008x6 Tee 22 Ea $271.00 $5,962.00

6" Valve and Box 141 Ea $1,275.00 $179,775.00

Trenching 56283 CY $2.82 $158,717.12

Bedding(sand) 28141 CY $12.75 $358,802.00

Compaction(sand) 28141 CY $3.95 $111,158.27

6" Watermain 1410 LF $36.00 $50,760.00

Pressure Pumps 1 Ea $10,000.00 $10,000.00

Main System Pump 2 Ea $15,000.00 $30,000.00

Total $1,568,846.33

XVII. STORM WATER MANAGEMENT

17.1 General CommentsStorm water concerns occur only in Zone 2. A 42 culvert has been designed tohandle the runoff and disperse the flow under Interstate 40. Other storm watercontrol structure designs will be left up to the contractor. The price for the 42 culvertwas costed using the RS Means Construction Cost Data. The costing data is shownin Table 11.

Table 11: Storm Sewer Culvert

Culvert Totals

42" x 29" size $151.00

Amount of Pipe 100

Price $15,100.00


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XVIII. CONCLUSIONS AND RECOMMENDATIONS

Fundamentally, this design consists of a collection network to gather wastewater,which is then funneled toward and through the water treatment plant, and issubsequently pumped directly back into the distribution line and to individual homesand businesses. At the heart of the treatment plant are membrane bioreactors and

reverse osmosis membranes, both units employing membrane technology to reducethe footprint size of the plant and produce high quality drinking water in an attempt toshrink the water cycle. Each component in the plant was chosen for its robustnessand its ability to handle variations in influent sanitary sewer flow composition.

An important limitation of our project to address here is the modularity of the plant.At this point, we have designed under the assumption that all phases of both theRRMF and the RCSs plans come to be in the next two decades. Due to theambiguity of not only the plans we had available but also the opinions of the contactswe talked to, any design based on incremental phasing was not a possibility. Ourdesign, in an economic sense, is the lowest investment possible. The majority of our

chosen equipment is the smallest of its variety and will not be able to handle anylower flows than 100,000 gal/day6. This constraint would force Rehobothsdependency on Gallups wastewater treatment facility until the full plant has beenconstructed and all future developments have been built in their entirety.

However, if the proposed treatment plant were built, Rehoboth would gain asignificant amount of agency. The region is presently, and will be even more so inthe future, in a water rights feud. Gallup has offered to annex all of the Rehobothland and provide the area water treatment as well as drinking water, but Gallup has aless beneficiary motive; by annexing the region it would also gain full possession ofwater rights. This puts in Rehoboth in a terribly dependent position on Gallup, which

will then charge the small town inordinately expensive fees for water access. Thewater production plant gives Rehoboth the ability to be self-sufficient in terms ofwater production and it retains valuable rights to water in a very water deprivedregion.

Below, in Table 12, is a complete cost outline from site preparation through theredistribution watermain. Also included are the 20% contingency and yearlyoperational costs associated with both the piping networks and the treatment plant.

6This value was obtained by comparing the varying equipment within the plant and determining that the

MBR was the limiting flow factor.


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Table 12: Total Combined Cost Estimate

Name Constructed Cost Operational Cost

Site Preparation $54,649 --

Sanitary Sewer $2,950,000 $3,000

Lift Station $120,000 $16,000Pretreatment $300,000 $1,400

MBR $910,500 $9,700

Solids Handling $616,885 $23,000

RO $405,939 $5,600

UV $81,000 $1,668

Chlorination $8,400 $1,800

Plant Operators (2) -- $60,000

Pumping Station $17,595 $8,593

Watermain $1,500,000 $20,000

Contingency (20%) $1,392,994 --

TOTAL COST = $8,357,962 $150,761

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