This is a digital document from the collections of the Wyoming Water Resources Data System (WRDS) Library.

Transcription

1 This is a digital dcument frm the cllectins f the Wyming Water Resurces Data System (WRDS) Library. Fr additinal infrmatin abut this dcument and the dcument cnversin prcess, please cntact WRDS at wrds@uwy.edu and include the phrase Digital Dcuments in yur subject heading. T view ther dcuments please visit the WRDS Library nline at: Mailing Address: Water Resurces Data System University f Wyming, Dept E University Avenue Laramie, WY Physical Address: Wyming Hall, Rm 249 University f Wyming Laramie, WY Phne: (307) Fax: (307) Funding fr WRDS and the creatin f this electrnic dcument was prvided by the Wyming Water Develpment Cmmissin (

2 CITV OF RA \NLINS. \NVONIIN r:; SAGE CREEK \NATER TRANSMISSION PIPELINE AND \NELLFIELD FACILITIES LEGISLATIVE EXECUTIVE SUMMARV DEC 19S6 JAMES M. MONTGOMERY, CONSULTING ENGINEERS, INC.

3 LEGISLATIVE EXECUTIVE SUMMARY CITY OF RAWLINS, WYOMING SAGE CREEK WATER TRANSMISSION PIPELINE AND WELLFIELD F ACn.ITIES DECEMBER 1986 Prepared By: JAMES M. MONTGOMERY, CONSULTING ENGINEERS, INC. 161 Mallard Drive, Bise, Idah

4 TABLE OF CONTENTS Intrductin 1 Prject Descriptin 1 Prject Backgrund 1 Hydrlgic Investigatins fr Water Supply 1 Develpment Water Develpment Master Plan 2 Predesign f Nrth Platte River Water Supply 3 Imprvements Sage Creek Spring Rehabilitatin Investigatins 3 Hydrgelgic Evaluatin f the Nugget Aquifer 3 Level m - Rawlins Grundwater Prject 4 Phase I - Well Drilling and Interim Reprt 4 Phase II - Final Design 7 Prject Cst Estimates/Financing 7 Prject Schedule 8 Water Supply Operating Plan 8 Operating Plan Criteria 8 Page N. Future Water Supply Operating Plan 10 Phase 1 - Maximize Delivery Capacity f 11 Existing Sage Creek Pipeline Phase 2 - Develp the Nugget Wellfield and 11 Replace the Lwer Prtin f the Sage Creek Transmissin Pipeline t the Wellfield Phase 3 - Maximize Spring Output and Replace 11 Upper Sage Creek Transmissin Pipeline i

5 UST OF TABLES Table N. N.1 N.2 Estimated Nugget Well Field Yield Initial and Current Prject Cst Estimates Page N. 6 9 UST OF FIGURES Figure N. N.1 N.2 Overall map f the City's Water Supply System Rawlins Grundwater Prject Implementatin Schedule Fllwing Page N. Back Pcket 9 ii

6 INTRODUCTION The intent f this Legislative Executive Summary is t prvide a sum mary and status reprt n the City f Rawlins Sage Creek Water Transmissin Pipeline and Wellfield Facilities Prject fr review by the 1987 Wyming Legislature, the Rawlins City Cuncil and the Rawlins Water Develpment Cmmittee. PROJECT DESCRIPTION The Sage Creek Water Transmissin Pipeline and Wellfield Facilities Prject, shceduled fr cnstructin in 1987, cnsists f the fllwing cmpnents: Installatin f 55,000 feet f 2A-inch diameter water tranmissin line t replace a majr part f the deterirated 16-inch wd stave pipeline frm the City's Sage Creek Spring water supply_ Installatin f 4,000 feet f 16-inch and 7,000 feet f 20-inch diameter water transmissin line cnnecting the existing Sage Creek Water Transmissin Pipeline t the new 24-inch line. Installatin f 3,300 feet f 8- t 14-inch diameter wellfield cllectin lines t cnnect three wells int the Sage Creek water supply system. The three wells, each drilled int the Nugget Frmatin and with a cmbined flwing yield f apprximately 900 gpm, were installed in 1984 and 1985 and were funded by the Wyming Water Develpment Cm missin. Prvisins were als made in the design fr cnnectin f up t three additinal wells and an installatin f a bster pumping statin t increase wellfield yield. T aid the reader in understanding the City's existing water supply cnfiguratin and the Sage Creek Water Transmssin Pipeline and Wellfield Facilities Prject, an verall map f the City's water supply system and prpsed prject is shwn n Figure N.1 in the back cver pcket. As a status reprt, this Executive Summary is current thrugh December PROJECT BACKGROUND The Rawlins Sage Creek Water Transmissin Pipeline and Wellfield Facilities Prject is a majr step in the implementatin f the City's \Vater Develpment Master Plan as adpted by the City Cuncil in April A brief histry f water supply investigatins leading t the cmpletin f the Master Plan and prjects cmpleted as the result f Master Plan recmmendatins which led t the current prject are prvided belw. HYDROGEOLOGIC INVESTIGATIONS FOR WATER SUPPLY DEVELOPMENT In April 1982, James M. Mntgmery, Cnsulting Engineers, Inc. (JMM) was selected t cmplete the Hydrgelgic Investigatins with the purpse f identifying and evaluating grundwater surce areas with reasnable ptential fr water supply develpment. Assisting JMM was the firm f Andersn & Kelly, Cnsultants -1-

7 in Engineering and Gelgy. After evaluatin f all grundwater surce areas within the Rawlins area, thse that exhibited the best ptential fr develpment were selected fr further evaluatin thrugh a test well drilling prgram. The final recmmendatins fr grundwater develpment (Nugget and Clverly Frmatins) were based n the test well drilling and pumping results and were incrprated int the verall Water Develpment Master Plan. WATER DEVELOPMENT MASTER PLAN In July 1982, JMM initiated wrk n the City's Water Develpment Master Plan as a Level I - Recnnaissance Study funded by the Wyming Water Develpment Cmmissin (WWDC). The Master Plan included a series f recmmendatins fr new water supply develpment as well as imprvements t existing supplies t prvide fr the City's prjected water demands thrugh year The Master Plan was adpted by the City in April The Master Plan included a number f shrt and lng term implementatin recmmendatins in rder fr the City t be assured f satisfactry water supplies thrughut the 40-year planning perid. Shrt term recmmendatins included: Cnduct a detailed predesign study f the aging Nrth Platte River water supply system (riginally installed in 1898) t determine upgrade and imprvement requirements t extend its useful life as lng as csteffectively pssible. Thrugh field investigatins, determine the feasibility f increasing the yield f the City's Sage Creek springs, r the develpment f additinal springs in the same general area. Cntinue investigatins f develping a 1400 t 1600 gpm grundwater supply frm the Clverly and/r Nugget Frmatins in the Sage Creek Basin. Replace the deterirated and undersized lwer Sage Creek water transmissin line between the anticipated Clverly/Nugget wellfield and the City's strage reservirs near the water treatment plant (a distance f apprximately 12 miles). In additin t being in a very deterirated cnditin, the existing Sage Creek transmissin line frm Rawlins Reservir t the City des nt have sufficient capacity fr future needs. The line is mstly wd-stave pipe riginally installed in The csts f maintaining the 30-mile pipeline have been apprximately $40,000 t $50,000 per year in recent years. In cnjunctin with the Nugget wellfield develpment, the Sage Creek transmissin line must be replaced with 24-inch line. Over 80-percent f the $40,000 t $50,000 per year pipeline maintenance csts are assciated with this sectin f the line because mst f the leaks and repair banding ccur belw the wellfield area. Upn adptin f the Master Plan in April 1983, the City immediately initiated a series f prjects t implement the Master Plan recmmendatins. Descriptins f these prjects fllw. -2-

8 PREDESIGN OF NORTH PLATTE RIVER WATER SUPPLY IMPROVEMENTS SAGE CREEK SPRING REHABILITATION INVESTIGATIONS Cncurrent with the Nrth Platte Imprvements Predesign, JMM als cmpleted field investigatins t determine if the yield f the City's existing Sage Creek Springs culd be increased thrugh rehabilitative measures. This prject was als funded thrugh DEPAD. Based upn actual rehabilitatin f three representative spring cllectin systems, it was estimated that the yield f the entire spring cllectin system culd be increased by 30 t 40 percent (frm an average annual rate f apprximately 1600 gpm t 2160 gpm) thrugh a full-scale rehabilitatin prgram and that five additinal springs may be develped fr an additinal 350 gpm supply. The full-scale prgram was cmpleted by City frces in the summer f 1985 and the verall spring system yield was estimated t have increased by at least 30 t 40 percent, as anticipated. HYDROGEOLOGIC EVALUATION OF THE NUGGET AQUIFER This prject, initiated by Andersn & Kelly, Inc. in June 1984 and funded by the WWDC, was cnducted as a Level IT Feasibility Study t develp infrmatin n the water prductivity f the Nugget Frmatin and t cnduct lng-term mnitring f the Nugget and Clverly Frmatins. In general, the scpe f wrk included drilling, lgging, develping and testing f a well in the Nugget Frmatin (Nugget Well N.1); testing f the City's existing Clverly Well; acquisitin and installatin f lng-term mnitring equipment fr bth wells; and evaluatin f data and preparatin f a final reprt. In brief, the reprt cnclusins cnsisted f the fllwing: Based upn step, lng-term and recvery tests f Nugget Well N.1, it was prjected that yield f the well (withut interference f ther wells) wuld be apprximately 350 gpm. Develpment f a 1000 t 1100 gpm water supply frm the Nugget Frmatin appeared feasible with the installatin f apprximately five wells. A smewhat lwer yield ( gpm) was prjected if the supply is utilized n a year-rund cntinuus basis. It was prpsed t install at least ne additinal well (and preferably tw) t cnfirm the abve estimates and t finalize wellfield design. A dependable water supply culd als be develped frm the Clverly Frmatin althugh the anticipated individual well yields f 75 t 125 This prject was initiated by JMM in July 1983 as a detailed evaluatin f imprvement requirements t the City's existing Nrth Platte Water Supply. The estimated csts f recmmended imprvements were used as a basis f cmparisn t the csts f develping ther surces f supply. This was t determine if upgrading the Nrth Platte supply was warranted r if ther alternative surces f supply culd be develped at a lwer cst. It was fund that majr imprvements t the Nrth Platte supply were nt cst-effective when cmpared t ther water supply alternatives. Hwever, sme imprvements will be funded t maintain the system's peratin, at least fr the immediate future. Funding fr the Nrth Platte Predesign was prvided thrugh the Wyming Department f Ecnmic Planning and Develpment (DEPAD). -3-

9 gpm wuld be cnsiderably less than the Nugget wells. Because well spacing wuld have t be 3/4 t ne mile apart, the nly ecnmical way t develp the Clverly supply wuld be t install wells very near the Sage Creek transmissin line. Since the Clverly wells wuld be further suth than the Nugget wells, replacement f cnsiderably mre transmissin line wuld be required t facilitate the Clverly develpment at this time. As a result, it appeared mre apprpriate t develp the Clverly supply in the future when replacement f the Sage Creek Transmissin Line frm the Nugget wellfield suth t Rawlins Reservir is required. LEVEL m - RAWLINS GROUNDWATER PROJECT Based upn the recmmendatins in the Vlater Develpment Master Plan and subsequent engineering studies and test well drilling discussed abve, the City f Rawlins requested funding frm the WWDC fr a Level ill Design Prject cnsisting f drilling tw additinal Nugget wells, predesign/design f the well field cllectin system and replacement f the lwer Sage Creek Water Transmissin Line frm the well field t Rawlins. Funding was apprved, and in June 1985, JMM was retained t cmplete the current Level ill - Rawlins Grundwater Prject. This prject is nw referred t as the Sage Creek Water Transmissin Pipeline and Wellfield Facilities Prject. The prject was t be cmpleted in tw distinct phases as described belw. Phase I - Well Drilling and Interim Reprt In the summer and fall f 1985 tw additinal wells (Nugget Wells N.2 and 3) were cmpleted in the Nugget Aquifer in the vicinity f the Nugget Well N.1. Well N. 2 was flw tested at a rate f 650 gpm fr seven days in late July and early August. Well N.3 was flw tested in August fr a perid f tw days. At the end f the flw test the flw rate had declined t apprximately 85 gpm. The data frm the flw test shwed that the transmissivity in the very immediate vicinity f the well was very lw. Hwever, at a shrt distance away frm the well the transmissivity appeared t be cmparable t that fund at Well N.2. Based n the test data, an aquifer stimulatin was cnducted n the well in Octber. The stimulatin cnsisted f fracturing the frmatin under high pressure by injecting water and a water and sand mixture int the well at high pumping rates. After the fracturing enhancement f the well, flw rates up t 900 gallns per minute were measured. In rder t assess the ptential yield frm the well field it was necessary t accunt fr the effects f the negative bundary in the area, interference between wells, the turbulent lsses assciated with the flw frm each well, and backpressure impsed n the wells frm the transmissin pipeline. The backpressure n the pipeline cntrls the amunt f available drawdwn in the wells. The wells have abut 140 punds per square inch (psi) shut-in pressure, but sme f this pressure must be used t vercme the pressure in the pipeline. The water transmissin pipeline will initially perate at a hydraulic grade line apprximately 115 feet higher than the individual well heads. At maximum capacity, frictin lsses in the pipeline will increase such that a backpressure f 205 feet will be impsed. The net effect f the backpressure will be t reduce well yield. -4-

10 Three head r backpressure scenaris were calculated fr the water transmissin line in the vicinity f the well field. The three scenaris cnsist f: Bster pumping statin installatin in the well field t relieve the backpressure n the wells frm the pipeline. This prvides fr apprximately 310 feet f available drawdwn in the well field and the wells will nt have t flw against the pressure in the pipeline. An initial 115 feet f pressure in the transmissin pipeline at the well field. This pressure was calculated based n existing spring and initial well flws cnveyed by the pipeline. This results in 195 feet f available drawdwn in the' well field. An ultimate 205 feet f pressure in pipeline at the well field. This pressure was calculated assuming the Sage Creek transmissin line is flwing at maximum capacity. This results in 105 feet f available drawdwn in the well field. Table N. 1 shws the predicted flw rates after allwing the well fields t flw cntinuusly fr 1, 10, and 40-year perids. Flw rates will be smewhat higher if the wells are nt used n a cntinuus basis. The table als shws the anticipated yields frm a well field cnsisting f 3, 4, 5 and 6 wells. The prjected flws as shwn n Table N. 1 assume future wells 4, 5, and 6 will be similar t flw frm Well N.1 which has the smallest yield f the three existing wells. Ttal well field yield may be several hundred gallns per minute higher if the future wells have yields similar t Wells N.2 and 3. In additin t the well drilling, a separate Interim Reprt was cmpleted in February 1986 and submitted t the 1986 Wyming State Legislature fr apprval prir t initiating final design f the wellfield cllectin system (Nugget Wells N. 1, 2, and 3) and transmissin line replacement. The key elements f the Interim Reprt include: Operating Plan fr incrprating the Nugget Aquifer water supplies int the City's verall water supply system and t determine water transmissin line size requirements. Cnceptual Design which in essence is a detailed predesign f all impryements required fr Nugget wellfield cllectin and cnveyance t the City via a new lwer Sage Creek Water Transmissin Line. Nte that as part f the Cnceptual Design it was determined t include prvisins in the Nugget Wellfield Facilities design fr installatin f a bster pumping statin fr the wellfield in the future. Identificatin f permits, easements and land purchases t implement the prject. Ecnmic Analysis t include an assessment f the City's ability-t-pay t aid the State in determining a fair and equitable financing plan, and a benefit-cst analysis f the prject. -5-

11 TABLE NO.1 ESTIMATED NUGGET WELL FIELD YIELD Years After Installatin 3 NUMBER OF WELLS (Yield - gpm) Zer Backpressure (Bster Pump Installed) Z Z Z Feet f Backpressure Z Z05 Feet f Backpressure Z NOTE: Yield is based n the assumptin that wells will be allwed t flw cntinuusly. -6-

12 Public meetings and hearings t advise the public f the prject and t gain its input. Phase n - Final Design After apprval f the Interim Reprt, final design was initiated n the Sage Creek Water Transmissin Pipeline and Wellfield Facilities Prject in May Final design activities, which will be cmpleted in January 1987, cnsisted f: Preparatin f detailed cnstructin drawings, specificatins, and cntract dcuments. Preparatin f Envirnmental Assessment Reprt fr the U.S. Bureau f Land Management. Obtain necessary cnstructin permits, easements, and land. PROJECT COST ESTIMATES/FINANCING In the Level ill - Phase I - Interim Reprt the ttal estimated prject csts t be funded by the City f Rawlins and the WWDC were identified t be $9,200,000. This cnsisted f the fllwing: Level II Actual Csts Level ill Estimated Csts Level IV Estimated Csts TOTAL $ 188, ,000 8,194,000 $9,18Z,OOO (Runded t $9,200,000) Als in the Interim Reprt, a detailed evaluatin f the City's "ability-t-pay" was cmpleted. Based n the findings f that evaluatin and input frm the City, it was requested that the WWDC make prject funding available t Rawlins n the fllwing terms. 62-1/2% grant fr $5,750, /2% lan fr $3,450,000 (48-year term at 4% interest) The 48-year term was prpsed rather than the maximum 50-year term t allw the City t defer lan payments fr tw years after prject cmpletin until ther City bnded indebtedness is retired. Based n the 4%/48-year lan, the City's annual lan retirement csts wuld be apprximately $163,000. This annual cst will, in effect, be reduced by O&M cst savings because f the prject. The additinal annual O&M csts f the prject are estimated t be apprximately $10,000 per year. Hwever, the City will realize an annual O&M cst savings f $40,000 t $50,000 per year because the deterirated lwer Sage Creek Transmissin Line will be replaced. Thus, the City will reduce its verall annual O&M csts by at least $30,000, with the net annual cst t the City prjected t be apprximately $133,000. Based n actual design csts, estimated cnstructin management csts, and estimated cnstructin csts prjected t the mid-pint f cnstructin, the ttal prject csts nw appear t be less than $9,200,000 estimated in the Interim Reprt -7-

13 and apprpriated by the 1986 Legislature. A cmparisn f Interim Reprt cst estimates and thse prepared in Nvember 1986 (based n 90% cmplete plans and specificatins) is prvided in the fllwing Table N.2. Based n the cst estimates in Table N.2, it appears that ttal prject csts may be apprximately $840,000 (9%) less than riginally anticipated and apprpriated by the 1986 Legislature. If the bids are as expected, all r part f the $840,000 shuld be reserved fr cnstructin cntingencies. PROJECT SCHEDULE In the February 1986 Interim Reprt, the schedule as shwn n the fllwing Figure N.2 was prjected fr the-sage Creek Water Transmissin Pipeline and Wellfield Facilities Prject. Final design authrizatin (anticipated at mid-april 1986) was nt made until near the end f May Hwever, the design (including agency review) was cmpleted by the end f December and prject bidding and award is schedule fr January and February Advertising fr bids will be initiated January 12 and the bid pening is scheduled fr February 10. Award f the cntract will be made by the end f February. After cntract signing and the btaining f bnds and insurance, a ntice-t-prceed t the cntractr is prjected t be issued by the first f April 1987, cinciding with the schedule n Figure N.2. A 240-day cmpletin is being required, which wuld place final cnstructin cmpletin at the end f Nvember 1987, als n schedule. OPERATING PLAN CRITERIA WATER SUPPLY OPERATING PLAN In develping a water supply perating plan fr the City f Rawlins, the cnstraints assciated with the City's water rights are f primary imprtance. Althugh the City has a relatively large senir water right frm the Nrth Platte River and at the Sage Creek Springs, the rights prvide fr direct flw nly and d nt allw fr strage. The City's strage rights are relatively junir and during drught cnditins are subject t regulatin by mre senir strage right hlders. As a result, the City's pririty has been t develp additinal water supplies and shrt- and lng-term perating plans which wuld: Maximize the use f the senir direct flw Sage Creek Spring rights. This wuld be pssible thrugh increasing the yield f the existing springs, develping additinal springs, develping surface supplies thrugh transferring part f the springs' water rights and diversin pints, and increasing the capacity f the Sage Creek Transmissin Line. Minimize the dependency n the junir strage reservir rights. Strage may nt be available r culd at least be seriusly depleted during drught cnditins. A transmissin line with a larger capacity t take advantage f direct flw water rights wuld serve t decrease dependency n strage. -8-

14 TABLE NO.2 INITIAL AND CURRENT PROJECT COST ESTIMATES February 1986 Interim Nvember 1986 Ite m DescriEtin ReErt Cst Estimate Cst Estimate Level n Prject $ 188,000 $ 188,000 Level m Prject 800, ,000 Level IV Prject - Wellfield cnstructin including well equipping, wellfield cllectin piping and transmissin line cnnecting ld and new Sage Creek Rad Transmissin Lines $1,546,000 $1,544,000 - Sage Creek Transmissin Pipeline including cnnectin t Atlantic Rim Reservir 5,705,000 5,218,000 - Engineering design & cnstructin management 725, ,000 - Legal and administrative (3% f abve ttal) Ttal Level IV Csts $8,194,000 $7,476,000 TOTAL PROJECT COSTS $ $ z

15 MILESTONE FINALIZE INTERIM REPORT 1985 N)O I J IFIMIAIMIJ)JIAtslINIO J)F-lMIAIMIJIJ IAISllN REQUEST LEVEL IV FUNDS INTERIM REPORT PUBLIC HEARING RECEIVE LEVEL IV APPROVAL FINAL DESIGN OBTAIN EASEMENTSI PERMITS AGENCY DESIGN REVIEW BID AND AWARD CONSTRUCTION FIGURE NO.2 RAWLINS GROUNDWATER PROJECT IMPLEMENTATION SCHEDULE

16 Incrprate grundwater supplies int the system t eliminate the current ttal dependency n surface and spring water supplies. This wuld cnsist f develping a grundwater supply t meet minimum water demands (940 and 1210 gpm in year 1990 and 2025, respectively), and maximize its year-rund use by blending with higher quality surface and spring supplies. Minimize the use f the Nrth Platte River supply due t its high peratin and maintenance cst. In additin t the abve pririties in develping a mre reliable water supply system, the City is desirus f increasing the system's flexibility, and having a system that allws fr phased cnstructin (bringing additinal supplies n line when needed). The system shuld als allw fr ease f cnnectin t and peratin with the Little Snake River Water Management Plan (LSRWMP) - Fish Creek Alternative, shuld it be implemented. The LSRWMP was an investigatin authrized by the Wyming legislature t evaluate alternatives fr trans-basin diversin f Little Snake River water acrss the Cntinental Divide int the Nrth Platte drainage. The water wuld be stred and made available fr use by cities, twns, and ther users. The Fish Creek Alternative wuld appear t be mst cnducive fr use by the City f Rawlins. That alternative wuld cllect water frm the Fish Creek drainage n the west side f the Divide and stre it in the prpsed Fish Creek Reservir. Frm there, a tunnel wuld cnvey water acrss the Divide int the Sage Creek Basin where it wuld flw by gravity in a pipeline paralleling Sage Creek t the Nrth Platte River. Since the prpsed LSRWMP pipeline alignment wuld be reruted thrugh Sage Creek Basin paralleling Sage Creek, it wuld simply be a matter f extending and cnnecting the Sage Creek Rad Transmissin Line int the LSRWMP pipeline (as shwn n Figure N. 1 in the back cver pcket) if and when that prject is cnstructed. Instead f develping additinal surface flw within Sage Creek Basin, LSRWMP plan water culd be used depending n the cst t the City. In additin, the City may be able t transfer its pint f diversin f the Nrth Platte supply t a tap n the LSRWMP line and nt have t purchase the water. FUTURE WATER SUPPLY OPERATING PLAN Based n the results f the recent (1983 thrugh 1985) water supply investigatins and imprvements, the results f Nugget Aquifer drilling (Nugget Wells N.1, 2, and 3), and findings f the Interim Reprt, all f the abve perating plan criteria are still very valid. In the lng-term, a water supply develpment and perating plan that wuld achieve the fllwing gals wuld be in the best interests f the City taking int cnsideratin the physical make-up f its current water supply system and water rights cnstraints: Limit strage requirements t n mre than that which is currently available in Rawlins, Atlantic Rim and Peaking Reservirs. Always maintain a grundwater supply t meet minimum water requirements during a drught cnditin. -10-

17 Size Sage Creek Water Transmissin Line replacement t be able t accmmdate either additinal spring and surface water develpment in the upper Sage Creek Basin r LSRWMP water r a cmbinatin f the tw. Reduce the use f the existing Nrth Platte supply. T meet the estimated year 2025 average daily water demand f 3875 gpm, and t achieve the abve gals, it is recmmended the fllwing plan f peratin be utilized. Phase 1 - Maximize Delivery Capacity f Existing Sage Creek Pipeline With the increased available spring supply, divert sufficient flw t maintain the Sage Creek pipeline full year arund. Shuld insufficient spring flw be available during part f the year, surface water frm Rawlins Reservir shuld be used. The upper transmissin pipeline capacity (abve the current lwer Sage Creek Transmissin Line replacement) is apprximately 2000 gpm. Phase Z - Develp the Nugget Wellfield and Replace the Lwer Prtin f the Sage Creek Transmissin Pipeline t the Wellfield Three wells within the Nugget Well Field have been develped with lng-term capacity f apprximately 900 gpm under 115 feet f pipeline backpressure. As demands increase cnsideratin shuld be given t increasing the well field yield t an estimated lng-term yield f 1340 gpm with additin f three mre wells and a bster pump statin. At the 1340 gpm rate, additinal Nrth Platte water wuld have t be used fr blending purpses. This will nt be required when the upper Sage Creek Transmissin Line is replaced and mre Sage Creek spring water can be utilized (see Phase 3 belw). Phase 3 - Maximize Spring Output and Replace Upper Sage Creek Transmissin Pipeline It is currently estimated that spring rehabilitatin effrts plus the additin f currently undevelped springs can prvide apprximately 2850 gpm frm that surce. Replacement f the upper prtin f the Sage Creek pipeline will be required when additinal spring flw is needed t meet demand r peratin and maintenance csts f the existing upper Sage Creek Transmissin Line becme excessive. The cmbined estimated ultimate average annual capacity f the Sage Creek spring supply and the Nugget Well Field is 4200 gpm. That will prvide sufficient water t meet year 2025 demand. In additin, the Nrth Platte supply shuld be utilized during extreme cld winter mnths t prevent pipelines frm freezing and t maintain thse facilities in gd wrking rder. That supply shuld be maintained as a supplemental r emergency backup t the Sage Creek and Nugget Well Field supplies as well as t maintain the City's water right. -11-

18