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u.s. DEPARTMENT OF THE INTERIOR US GEOLOGICAL SURVEY Abstract Sedllnents deposited in Tell<lce Reservoir contain large cOIlt;mlraliom of mice me!ak A ~tuJy was 110m; by HI(; ILS Gco]nglC:l] Survey, In coope,rarion will1lhe ILS EnvJr{;nme11T,11 Prole,coon Agency, to map the Cum:nt (1994) buthymetJk (bottom) surtace to estImate the current storage capacity of Terrace Reservoir and the \-o]ume of sediment deposited in the reservoir during 19:<' 1-94. A better understanding of the bathymetric surface and changes in that sulface caused by deposition of tral.:c-mctal. enriched sediments will allow the U.S. Environmental Protection Agency to ChOOM; appropnate remediation plans for Terrace Reservoir. The 1994 bathymetric-surface map of Tcrracc Reservoir was machine contoured from 21,944 depth soundings. Depth sound- ings were made with illl echo sounder during Jul~ and August [994. A storage-capacily table of the reservoir was estimated from the 1994 bathymctric-surlace map. Comparison of the July-August] 994 swrage capacity with estimated 1981 storage capacity indicated a decrease in storage capacity of about 580 acre-feel, below a ~tage of 8,545 feet. Aver- age annual deposition of sediments in Terrace Reservoir during 198 ]-94, below a stage of 8.545 feet, was assumed to cLJual the average annual decrease in storage capacity and 'Was an estimated 41 acre-feet. The thickness of sediment deposited in Terrace Reservoir during 1981-94, below a stage of8,545 feet, averaged about 2.7 feel. INTRODUCTION Sediment deposited in Terrace Reservoir, Conejos County, Colorado. contains large concentrations of trace metals (A.J. Horowit7 and others, U.S. Geo[ogica[ Survey, written eommun., 1995). The volume oftrace-metal-bearing sediment stored in Terrace Reservoir had not been determined previously. However, the bathymetric surface >,>,as mapped from aerial photographs taken when Ihc rescrvoir was drained for maintenance in 1981, and the storage capacity was estimated from that map (Davis Engineering Services, Inc.. 19R I). Sources of tracc metals in the Alamosa River Basin, upstream from Terrace I Reservoir, include outcrops of mineralizcd rocks and mined areas. Mining of gold in thc Alamosa River Basin began with the discovery of gold at Summltville in 1870. The Summitville Mine was operated as a largc-tonnage, open-ph, heap-leach gold mille during 19R6-92. On December 6, 1992, the operators of the Summitville Mine deelared InmkrLJplcy ~nd :-th:-m(!nned the site al1d Th~ l:,~. -unylronmentl11 Pl\!I..:l.:lioll Ag":IICY (ErA) assumed operatlon of the ~iL..: ulnl ill":l,,:us!.:ll wl:I[!.:I-lrel:lITTH:nll.:-tp:-tl:lty at the, sue, to mml Illi/,!.: disdmrgl: or Inw-lllll1lity w:Her to the, Wtghtm,tn 1'01'11:. (i uibutalY orLIl": A]mllllsu RIver (hg_ 1), M1I1lLl~ actlvities have uff..:l.:l..:u l.:orn':l.:llllaliuns or Irm:e mC,!:1[S m Sl1rtar.e wuL":1 ill Lll": husill. OHllp1111Sl111 nrpn~-lqX" and post.Il)~5 data Illdlci:\te that pH deo,;l":Ual.:U ':mil Gonr.enrratlons ot dIssolved ....nd total or L\!Lul-ll.:l.:l!v":luhk Imce mcl11[S (clIppc,r, mlll, aLld po~~ibl~' t.illl.:) im;ll.:as~ill ill Ill(: AI11mm:-t T~lv~r dnwm:tre'am trom 1tI; confluence with Ih!.: WiL'lllrmm Fork (Cmn, I\;lYJ} Detuiku aLwlil.:s of lll": wulcr qlmlily, limno[or,y, sf'Jllment de,poslUon ilnd geochem- islry, :md movemenr ot merals mto_ wlthm, .;l.nd thfOU~h Teu'o.o,;e R,,:sl.:lvoil h..:gall ill 1994 by the U,S. Geolo)?kal SUlVI:Y, illl.:m'JI":lulilm wilh Ihe EPA (f'l1in, IYY"l) A Cllmnt lldlllilion nr Ihl~ h~lth)'metrlc surface and ot Th~ volume ofuace-mel-l1I-1)l.;lIIillg sl:liilln':lll~ d~po';ITed III the reservoil call b..:: u.,..:u b~' Lh.: EPA irr sdcdion or 11pprnprl:1te actl0l1s tor r!.:Hll:l11111111n nr Tl:IT:H"~ I(CS('TVOlr, ThtS 1\"'pon presentS the results fJOm ll. ~luuy L]lal wus done to map the current (July-August 1994) configuration of the bathymetric surface to estimate the current storage capacity of Terrace Reservoir and the volume of sediment : deposited in Terrace Reservoir during 198 ]-94. Fie[d work for the study was done in July and August 1994. Location and Description of Terrace Reservoir Terrace Reservoir is located in Conejos County. Colorado, ahout 1 fi mi south- wuthwest of Monte Vista and about [2 mi downstream from the confiuence of the Alamosa River and the Wighlman Fork (fig. I). ""'ater released from Terrace Reservoir is uscd to irrigate about 45,000 acres offarm[and in the San Luis Valley of south-central Colorado (V.S. Environmental Protection Agency, [9(3), I Terrace Rescrvoir is impounded behind an earth-fill dilln that was completed across the Alamosa RIver Canyon during 1912. The sides of the reservoir are rocky and stcep. I The crest of the overflow spillway of Tenllce Reservoir is at an approximate altitude I ofR,571 ft aboye NGVD of 1929. At maximum stage (8.571 ft above NGVD of 1929), I the reservoir is about 14,000 ft long; ranges from a few feet to about] ,500 ft Wide: and I has a surlace area of about 299 acres. The storage capacity of Terrace Reservoir at maxI- mum stagc was reportedly about 15,182 acre-ft in ]9X] (DaVIS Engineering Services, lnc., 1981). Based on high-water marks. reservoir stage generally is less than about 8,504 ft above NGVD of 1929. The storage and releasc of water from Terrace Reservoir for irrigation alTects the distributIon of sediments within the reservoir. During the fall through late spring, when water is stored for later release, sediments are deposited in Ihe upstream one-thud of the reservoir. During the summcr, when water is released for irrigation, reservoir stage drops rapidly and much of the sediment, which previously was deposited in the upstream one-third of the reservoir, is transported to and deposited in the downstream two-thirds ol"the rescrvoir. Between June 28 and August 12, ] 994, the reservoir stage dropped about 130 ft and much of the sediment In the upstream one-third of the reservoir was eroded and transported farther downstream in the reservoir. Data Collection The bathymetric surface of Terrace Reservoir wa~ surveycd during July and August 1994, using an echo soundcr (ODECO TDS-lOOO) mounted on a hoat. Soundings were made on a fixed time interval while the boat traveled at a relatively constant speed of about 2 to 3 mi/h. The location of each sounding was computed from the distance and azimuth from a known position on the shore (navigation slation) to a targel mounted on the boat about 6 ft above the echo sounder's transducer. Distance and azimuth were determined with a HYDR02 naVigation system. Distance from the naVIgation station to the target was measured using an infrared range finder. Azimulh from the navigation station to the target was measured wJth an e1ectronrc surveying instru- I ment (total data station). Data from the echo i>OUl1dcr, the l1lnge finder, and thot 100ul JaLa station were slored and processed in the field on a laptop computer. using a hydrographic~ surveymg software package (Coastal Oceanographi\:s, ] 994). [The use of trade, product, industry, or fiml namcs is for descriptive purposes only and does not imply endonement by the U.S. Government.1 I Each sounding depth (depth to reservoir bottom) was converted to a hottom alti- tude by subtracting the sounding depth from the reservoir stage. Reservoir stage was determined twice daily, using temporary staff gages. When necessary, the stage was interpolated to estImate the stage at the time the depth sounding was made. Tcmporary , staff gages were used because the stage recorder for thc rcservoir was inoperative during July and August [994. Datum for the temporary staff gages was a mark on the crest of the overl1ow spillway of Terrace ReservOIr (EM-I. fig. 2), which is approximately 8,571 ft above NGVD of 1929. Soundings were not made in the upstream one-third of the reservoir, upstream from : navigation station TP-6 (fig. 2). because the boat was dIfficult to handle in the shallow i and relatively narrow channel. Becausc no soundings were made west of naVIgation slation TP-n. the bathymetric sUlface of the reservoir upslream from TP-6 and abovc a stage of about 8.550 ft was not surveyed. Soundings in the middle one-third of the reser- voir, between navigation stations TP-6 and TP--4. were made on July 1, 1994. when reser- voir stilge was 8,559.1 ft, and in the lowcr one-third of the reservoir, downstream from navigation statIon TP-4, during August 10-12. 1994, when rcservoir stage was betwcen 8,533.8 llild 8,534.0 ft. Traces along which soundings were taken are shown in figure 2. Horizontal coordinates of the depth soundings uscd in thIS report are given as easting (distance east) and northing (dislance north) from the datum that was used for a previous '(!9R]) survey of the bathymetric surlace of Terrace Reservoir (Davis Engineering Services, Inc., 1981). The locations of two prominent features (BM-l and HUB-I, fig. 2) were used lo register the coordinate locations from this survey with the coordinate locations from the survey by Davis Engineering Services, Inc. (1981). I3M-l (fig. 2) is a mark on the crest of the overflow "pill way adjacent to the north wingwa]1. HUB-l (fig. 2) is a 2-ft-Iong iron rod, near a boulder on a prominent pOInt of rock, north of the east end of the earth-fill dam. After ediling to remove spurious and duplicate data pomts, a total of 2],944 bottom altitudes were used to define the July-August 1994 batllymetrie surface of Terrace ReservOlr. , Acknowledgments I , The fo]]owmg indlVldtl.:l1s ilnd organizatiom are aCknowledged for plovidlng illful'- mation and acee~s lo privale propcrty. Paul Priekdl or the Terr:lce ReservOir lrrlg.'1tian Company provided unpubli~h"x1 stage mcaSlllcments for the reseJ'voiJ', anJ the Terrace Reservoir Irrigation Company allowed access to the reservoir for the balhymetric survey. Davis Engineering Services, Inc., of Del Norte. Colorado, provided a base-stable copy of the 1981 bathymetric-smace map and a copy of the] 981 storage-capacity table for , Terrace Reservoir. -I he State Engineer's Office, Irrigation Di\-ision 3, Alamosa, CQlorado, provided data on monthly storage in the reservoir. David S. Muc[]er, U.S. Geolo~cal Survey, provided training in use of the navigation system and hydrographic software. I BATHYMETRIC SURFACE 111e altitude and configuration of thc bathymetric surface of Terrace Reser~oir dur- , ing July-August ]994 (fig. 3) were machine contoured. using ARC/INFO (Environmental Systems Research InstiUlte, Inc., 1994). Selected machine-drawn contours were ~vised because of insufficient data spacing in some areas and because of inherent limitalipns of the contouring program. The coordinates used on the 1994 bathymetric-surfact map (Jig. 3) arc in feet east (easting) and feet north (northing) of the datum that was USfd ~ , by Davis Engineering Services, Inc. (1981). Although the coordinate system is b~sed on the State-Plane Coordinate System for southern Colorado, the locations have not been determined preci~c1y. Thercfore, the local coordinate system used by Davis Engmeering , ServIces. Inc. (1981), was maintained for comparative purposes. Because no new data were collected in the upslream one-third of the reservoir west of TP-6 (fig. 3), the 1994 bathymetric surface was not contoured in this area. Contours also arc not shown where altitude of the surface is greater than 8,550 ft in the lower l>,>,-o-thirds of the reser- voir because little data were collecled when the stage of the reservoir was greater than 8.550 ft. Changes in the configuration of the bathymetric surface between altitudes of ;0;.:-'."0 tllHl X,." II 11 h11VC nnl hl~l~n lk,teMllmed. II0we.ver, substanTIa] qUilmltles of sedi- ments are not likely LO o.co,;ullluluL..: ubuv..: ullulLiLutll.: of llllllut R,SSO n in Ih~ lIpstream one-thIrd ot the,reserv01r west ot TP 6 (fig, 3) because of erosion dUlill~ l)\':liou~ wllcn LII": rt.:sl:rvllir ~Illg!.: limps r11pid[y 1md in the dowl1.~tre<lm two-thIrds at rh~ r~servoir !;Iee.lllse the Sides of the reservoir .ue vel Y ~\I:;qJ. The l\;lt(l and I\oN1 barhymernc snrtac~ In"ps .....ere slJllila.r in most wo;:us. DiITl:r- I:llo,;'..:s bdw":l:lI Llll: huLllymcLril: sur(acc~, in par!, qlll:lntilied the lIer:llmlllatmn ot S("()lmellTS In the reservotI betW~el' ]YS] (\nd 1 YY4 and also Indkated ~Ollll; Ull.:US ill'" llich I:lrllrS 111 cOlltnurin)! pmh11hly n:sllllcd rrnm imrrflicif'nt 1111t;" Some, dltterenc~$ belweelllhe 1981 and 1994 bathymeuic-sulrulCl: lIraps also lesulL!.:d from III!.: Iypcs or d:-tt:-t uSl~d tn prepare th(', maps The', IYl'.\1 bathynte[nc snrtace m"p (IJ(\v15 bn;<,lneeJill~ Sel vi..:..::, TlIc., 19R i') wus llrepflrl.:ll fnml m:rifll phlllncrllphs llib:n whl'n the reservOIr was dramed tor ntet/me n.-ulCe and e5semi;).lly cOlI,tiluted il":lJlltilluou:, uala ~t.:L. TIll.: 1994 balhymctrit:-!mrface map was prepared from a finite number of depth soundings (21.944) and constituted a discontinuous data set. Differences between the 19R I and 1994 bathymetric-surface maps also might have resulted from errors in determining locations of the navigation stations and soundings and in the measurement of depth and reservoir stage. The use of different omtouring methods also could introduce differences because the methods are interpretive. Errors ill depth measurement probably resulted from the vertIcal motion of the hoat due to waves or changes in velocity of the boat, but likely would have a mean error of zero and range from about -0.5 to 0.5 ft. Errors in sounding locations are likely to have resulted Jrom slight crrors in the measurement of the azimuth from the navigation station to the target mounted ahove the transducer of the echo sounder. Errors in measuring the azimuth probably were less than 1 degree. At a distance of 1.000 ft, an error of ] degree in the azimuth would result in an error in location of the sounding of about 17.5 ft. Although the accuracy of soundmg loeatlons cannot be detennined with the available data, it was assumed likely location errors were less than 1 to 2 ft. Errors in stage measurement included measurement of the stage on the temporary staff gages (-0.05 to 0.05 ft) and datum error (-0.02 to 0.02 ft) and are not a substantial source of emm ..- -- -" '--, -~ /i l , c' \ / c' \ ---' \ \./...,...Jf' //",><,'" ';-:~' ,rp-f:l \ _ ,//,<':'/,<'- I~;~~~// ,=, PREPARED IN COOPERATION WITH TI-IE U.S. ENVIRONMENTAL PROTECTION AGENCY 1981 reported 1 Table 1. Storage capacity of Terrace Reservoir, 1981 and 1994 ~;;f 3971 WATER-RESOURCES INVESTIGATIONS REPORT 96-4027 Watts, Kenneth R.. 1996,Bathymelricsurfscesndstoragecapaci ty of Terrace Reservoir. Conejos County, Colorado. JulV-August 1994 101" 10lJ"30' 10(1" Monte Vista o ~o 37' eo' Approximate Bastern boundaryofthe::---.... ... SanJusnMountains -........::.' , , , \ \ , , \ \ \ , , &. .( ~/,i. L.. .~ OJ- Summitville Mine Wightman Fork I Monte VIsta National Wildlife Ref:d AlsmosaNational W>ldllfeRefuge r-- 1981 estimated 2 1994 estimated 3 I Altitude o. water surface (feet) Surface area (acres) Surface area (acres) Storage capacity (acre-feet) 17.(01)N R,45a R,455 R,460 8,465 R,470 0.8 2.6 71 14.6 21.3 0.7 2.7 70 14.7 20.8 LO 94 33.5 87.7 176 8,475 8,480 8,485 8,490 8,495 22.3 37.4 49.5 58.8 71.1 284 434 651 921 1.250 29.4 38.8 49.9 60.0 74.0 --'-- '-. -, (- -.......~ ......... \ ~~- ~- --~ _ --..... TP-5 / 1-----(T~------ ~~=--->-- ... --... " . i "'~':i\ f ,.',A/ /.~ , i /\., I.. /' r !' \' - ! ", . / '- '~-\ or' "'" ,_ II c' ~-, -'::-,', '~, '_ :~:;._/<,_ -'::<,'::.'> ":,:::---"'" , ,c' ','::,"=. , . ~~~o "'(""~':"",-\, - '>~") .) '<'M",-" ',:~ :<'" --__..r.........~_ -- -":"""<':~"i~~?,,-_, -...... ~ ~ "-, 1 ,.;/ J 2,OOOE Base modified from Davis Engineering Services, Inc. (1981) STORAGE CAPACITY The ~lOragc capacity of Terrace Reservoir during July-August 1994 (table l) was estimated from the 1994 bathymetric-surface map (fig. 3), using ARCIINFO. Although the storage capacity of Terrace Reservoir during 19R 1 (table 1) was reported by Davis Engineering Scrvices, Inc. (1981). for purposes of comparison, the 1981 storage capacity was estimated from the digitized 19~1 bathymelric-surface map, using ARC/INFO. The difference between the 1981 reported and estimated storage capacity of Terrace Reservoir at a stage of 8.545 n (Lable 1), calculated as the reported 1981 storagc capacity minus the estimated 1981 slorage capacity. was -130 acre-ft. The 1981 estlmatcd storage capacIty was about 1.5 percent larger than the 19R [ reported , storage capacity. The difference between the 1981 and the 1994 estimated storage capacily of Tcrrat:e Reservoir at a su"1ge of 8,545 ft (tahle ]), calculated as 1981 estimated minus 1994 estimated storage capacity, was 580 acre-ft. The 1994 estimated storage capaClty was about 6,7 percent smaller than the [98] estimated storage capacity and was assumcd equivalent to the cumulative deposition of sedIments in Terrace Reservoir during 1981-94. Although the estimated change in storage capaciLy during 1981-94 was assumed to approximate the cumulative 1981-94 deposition of sediment, the difference in storage capacity also includes errors in dataco]]ection, in contouring the bathymetric data, and in calculating the storage capacity from the bathymetric surface. The average annual decrease in storage capacity of Terrace Reservoir at a ,<;tage of 8,545 ft, during 1981-94, \\-as less than or equal to abouL 41 acre-ft, or an annual decrease oJ about 0.5 percent of the estimated 1981 storage capaClly at a slage of 8,545 ft (table 1). Although sedime~t deposition was not assumed to be of uniform thickness within the re,<;ervoir at a st:Jge of , 8.545 fl, the ratio of cumulative decrease in storage capacity of the reservoir (580 fcre-ft) to the estimated 1981 surface area of the reservoir (215 acres) was about 2.7 ft an~ was assumed to be equivalent 10 Ihe average thickness of sediment deposited in ~1lrrace Reservoir during 1981-94. , A preliminary reVlew of the differences between the digItized 1981 bathy~tric- surface map (Dav1s Engineering Services. Inc., 1981) and the [994 bathymetric-surlace map (fig. 3) showed an irregular pattern of positive dlfferences (deposition) and negative differences (erosion). Most of the positive d1fference (deposition) was in the middle one-third of the reservoir between 1,500 and 6,000 ft casting. An apparent irregular pattern of positive and negative differences in the dov.-nslTeam one-third of the reservoir was assumed to primarily result from data and contouring errors, ! CONVERSION FACTORS AND VERTICAL DATUM 16000N , , , , , 96.2 112 127 117 147 161 '" 1R4 '" 8,500 8,505 8,510 X,'i1'i X}i20 X,.'l?~ X,.'ll!1 X,.'11'1 X,.'l40 94.0 108 126 116 I" I" '" 183 197 1,660 2,160 2.750 1,400 4,110 4,R70 :'1,700 6,;'\90 7,;'\40 "'" N 7'1, Jr-\ ( I; ',.Q!XlN - -- ,,--- (-- ,=, \ \ \ \ ) / / / ( \ --- Storage capacity (acre-feet) 19 10.4 346 !l!l.7 178 306 476 698 972 1,310 1,730 2,250 2.850 1.110 ~,.?20 ~,9Q0 :'i,~20 11,710 7/,(,0 Difference between 1981 reported and 1981 estimated storage capacity (acre-feet) -0.9 -1.0 -l.l -1.0 -2,0 Surface .... (acres) 0.7 4.0 85 ]4.6 20.6 Storage capacity (acre-feet) L7 13.5 44.8 102 190 308 457 647 878 t,16O 1,550 2,030 2,600 ),110 ~,::;~H,J 4,(1l1) ;',~~I) 1;,:.'41) /,141) Dilference4 between 1981 and 1994 estimated storage capacity (acre-feet) 0.2 -3.1 -10.2 -13.3 -12.0 37' -22.0 --42.0 -47.0 -51.0 -{oOO 26.2 33.3 43.0 49.2 65.0 COLORADO " o ~ ">0 'ee Farmlands Irrigated with AlamossRiverwater -70.0 -90.0 -100 -1111 -110 -1.'0 -1')0 -1).1) -1)0 88.1 106 120 130 LN l~lU lo:! 17' ," - Location Map 20 MILES , Mod,fled from King (19951 -2.0 19.0 51.0 94.0 150 o I o , 20 KILOMETERS 11,:'1-1'1 :lIt It:'!60 21:'1 R,(,Q() -llf1 },UU ;';,110 5llU llJuvl~ r:OJl:IIlCCrm!! Scf'llcc~.lnc. i19Hl). '~~rlw.'c l\i:CU rwu ~WI1\lC CUPUCl'Y cmmalCd frDTl1 dip;ltlr.<::d mal1 i'lfth(: h~rhYn1(:rrk. wlf~l"'" M n.IV;', F."glJl~~JilJ~ ~",vu.'~" 1I1L' (1~1::;1), ~~mJ; A1Kflf'.lrU. ~AL~lllUllJ L'lLI1JUJullV~ ""pw.'lly CmmUlCU fivm 19\>4lnllh)'m~lrlc ~Ilrfacc, U~in.tl AR(".JfNTiO. ~TlI(f~d~l11'~ llllL'ulult-d ''" I'l::;l ~~(lmu!J:1J ~WTlll!C ~lIpl\CIlY mmu~ 1994 cstlmal~d .~tfIraJ1:~ 'apacir~1' " , , " Figure 1. Location of Terrace Reservoir. 180 220 250 290 330 311U 43U 470 '20 17.000 llJ,UIIIl l!i,(Klll , w if'4,OOO . " z . ti:13.0oo o z TRACE OF ECHO SOUNDER PROFILE APPROXIMArE LIMIT OF TERRACE RESERVOIR-Shows app'o"matallm~ofTerraceReselVolrllllls1ageof 8,571 tee1above NGVD Of 1929 12,000 TP-1 . BM-t o CONrROLPOINTBM l~Showsloca1t<lnofhonzontalCOn1rojp-olntand datum BM-llsamarkontl>ecreSloftheoverllowsplllwlly,adlacent to tha north w,ngwllll. NAVIGATION STATION AND NUMBER 11,000 HUB-' o CONTROL POINT HUB-1-Shows locetlon of ho,lzontalcontrol f>Olnt HUB-1051l2-1ootlonglfonbarnaarabould<lronapromlnenlpolnl ofrock,northoltheeastendoftl>eearlh-hlldam l 4,000. - - --::.-- -co - -------- -'-''';'7~-~-_ , ./-" '-. " " " - . " --:-"~~ --...-....:..'>"-------. , - -- ~~~~---..->~>,--=:.-=- ..... - - - - '~......... -- ,_..___7___; h--"-'-::":"'~":::'~~~ -::c "':::''-' :--.... I, , '""~ i ./ ,h -~------.:::s I~ j '-..., ,~_~-_______ ( ,--_J \ " '~,\J '--.... '.. ,~ ~ Vi -, j-v~ Multfply s,OOOE ATlON APPROXIMA IT L1MIT OF TfRRACE RESERVOIR-Shows apprc>simate hmlt of Terrace Reservoir at a stage of 8.571 feet above NGVDof 1929 TP-1 I oc" aere-foot(acre-ft) foot(ft) mile (mi) mi]e per hour (mi!h) By To obtain 4,047 1,233 0.3048 1.609 1.609 square meter cubic meter meter kilometer kilomeler per hour -8550- ~--'- --- -- T1'-2 14,OOON 10,000 -3,000 -2,000 -1,000 o 1.000 2.000 3000 4,000 5.000 6,000 EAST lNG, IN FEET 7.000 8,000 9.000 TP-1 '. '. " I (J) BM-1 .' "" HUB-1 11,000 12,000 1,000 METERS BATHYMETmC SURFACE AND STORAGE CAPACITY OF TERRACE RESERVOIR, CONEJOS COUNTY, COLORADO, JULY-AUGUST 1994 By Kenneth R. Watts 1996 Figure 2. Locations of navigation stations, traces of echo sounder profiles, and apprOXimate limit of Terrace ReservOIr. [BM-1, a mark on the crest of the overflow spi[lway adjacent to the north wingwall, is a horizontal control point and datum. HUB-1, a 2-foot-long iron rod near a boulder on a prominent point of rock north of the east end of the earth~fill dam, is a horizontal control point. Easllng is the dislance east of the arbitrary meridian and northing is the distance north of the arbitrary baseline that was used In the 1981 bathymetric-surface map (DaVIS Engineermg, Inc., 1981).] ---f~ Figure 3. Genera[ized altitude and configuration of the bathymetriC surface of Terrace ReservOir, Ju[y-August 1994. 7,OOOE 4,000 FEET , TP-1 . OBM-' BATHYMETRIC CONTOURS-Show altItude of tne bathymelrlc surface Contour interval IS 5 feet Index contour mt",rvaI1hea\lY' Ime) IS 25 feet Dalum IS NGVD of 1929 NAVIGAllON STATION At>:D NUMBER .=, o ., CONTROL POINT 8M-1-Shows locahon 01 horizontal control pomt and datum. BM-l is a mark on the crest of the overflow spillway. adJ,,-c(;nl to the north wmgwall CONTROL POINT HUB-1-Shows locallon of horimnlal control pomt HL"B-1 is a 2-foot long iron bar near a boulder on a promment pomt of rock. tlorth of the easlend of the (;<Irth fIll dam L National Geodetic Vertical Datum of 1929 (NGVD of 1929): A geodetic datum derived from a general adjustment of [he first-order level nets of both the United Slates and Canada. formerly called Sea Lcvel Datum of 1929. REFERENCES CITED Cam. Doug, 1995, Faclor:s affecting surface-waler qualilY in lhe Ak-tTTlusa RIver Basin, I south-ccntral Colorado lab~.l, In Pose)', H.H., Pendelton, J.A., and Van Zyl, Dirk, eds., Proceedings-Summitville Forum '95, Jan. ]7-20, 1995, Fort Collins, Colo.: Culurado Geological Survey Special PublicatIOn 3R, p. 159. Coastal Occanographics, 1994, Hypack-VerSlOn 4.16 users manual: Durham, Conn., 247 p. Davis Engineering Services, Inc., 1981, Capacity survey of lhe Terrace Rescrvoir De] Norte, Colo., 3 sheets, scale 1 :2,400. Environmenlal Systems Rcsearehlnstitule. Inc., 1994, ARC/INFO-Version 7.0.2: Redlands, Calif. Kmg. T. V. v., ed., 199j, Environmenwl considt:l1ltions of active and abaIldoncd mint:d lands-Lessons from Summitvllle, Clllumdo: U.S. Geo]ogica] Survey Bulletin 2220. 3Xp U.S. Environmenta] Protection Agency. 1993, Sununilvil]e mining site "Background" fact sheet, January 1993. IOHUO.' .=, SCALE 1:4,800 o 1,000 I 2,000 3,000 I o 11:.', i-I-'-- , .. j}---~ --, SPILL 'AY 9.000E lO000E 11,OOOE 13000N 12,OOON I1,OOON 10000N 12,OOOE .~