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HomeMy WebLinkAbout9I HYDROLOGY IMPORT FOR PROPOSED GRAYli . MINjNr, M&T CmcO I MCH Prepared By St.evrn J. Deverel, Ph.D. Consulting Hydrologist P. O: BOX 2401 Davis, CA 95617 HYDROLOGY REPORT GROUNDWATER RESOURCES The proposed gravel mining site on the M & T Ranch is on the eastern edge of the Saeramonto Valley. Structurally, the Sacramento Valley forms an asymmetrical trough of uterine and continental alluvia, that 0'verlies a basement of granitic and metamorphic, rocks. Marine Cretaceous sandstones and shales that contain brackish water immediately overlie the basement rods. A scgttencc of contiamtel deposits of Eocene and post-liocone ago overlies the Crttaccous rocks at about 1200 to 19W f oet. This is dio base of the Tuscan formation which is the primary source of groundwater in the area. The base of fresh water. is about 500 feet above the base of the Tuscan formation_ Qu$1.e xalluvial fan and stream. channel deposits overlie the Tuscan formation at about 100 feet below land surface and arc also a source of fresh groundwater. The relevant and generalized hydrogeologic framework of the site is depicted in. cross section A -R (figures 1 and 2). The data for the generalized geohydrologic cross section (fi_ ure Z) were developed from drilling logs collected from the Department of Water Resources (DWR) and from holes drilled at the site. The general statigraphy of the area consists of go to 100 feet of Quaternary alluvial and stream channel deposits underlain.by the Tuscan formation: The Tuscan formation is an assemblage of Pliocene volcanic mud[lows and volcanic detritus as well as highly permeable sands and gravels. The Tuscan sands and gravels are the primary water -bearing aquifers for the region. These send and gravel aquifers are at depfhs of up to 1000 feet and are separated from each other by predominantly fine-grained deposits of low permeability. Groundwater flows under confined and semi -confined conditions. Figure 2 Chows that the deposits underlying the proposed site consist of an upperlayer of sandy clay that overlies about 60 to 70 feet of Quaternary sand and gravel deposits underlain by about 200 feet of primarily fine-grained and lithic Tuscan deposits. A lower, confined layer of sands and gravels of high penneab'ility at about 180 feet below sea level is underlain by less permeable deposits. 70 D -i.2 JUIrsgnd I kedians of Groundwater Plow Data for water levels and direction and rates of groundwater clow were obtained from DNVR in Red bluff. An investigation was conducted on the M &s T Ranch in 1992 and 1993 (Department of Water Resources, 19:93) in which data for water levels and pemaeability were - collected and analyzed. In addition, Hydrologic Consultants, Inc_(iiCl) of Davis, California developed a groundwater flow modet fbr the entire Butte Basin. in 1994 and 1995. Data from these two sources were used to evaluate rates of groundwatwr flow and inputs and outputs to the groundwater system at the proposed site. 1 conductivity and. groundwater hydraulic gradients for the -site (Department of Water Resources, 1993). The average regional hydraulic gradient is about. 3-5 feet per mile. This value for the hydraulic gradient is consistent with data presented in Hull (1984) for the water table and It was therefore assumed to apply to the shallow unconfine4 aquifer as well as the deep confined aquifer at the site. The hydmulle conductivity of the shallow and deep sand and gravel layers was assumed to be about 400 feet per day based on aquifer tests conducted by DWR- Using Darcy's law which describes the groundwater velocity as equal to the hydraulic conductivity, K, multiplied by the hydraulic gradient and dividedby a porosity of .35 (Freeze and Cherry, 1979), the velocity of groundwater flow in the upper and lower gravel and sattd layers is about 280 feet per year. The hydraulic conductivity value of l8 feet per day for the fine grained deposits was taken from Hydrologic Consultants, Inc (1996). 71 The water- table at the site fluctuates seasonally between about 7 and 14 feet below land surface (Department of Water Resources, 1943, 1496). Groundwater flows fYpm northeast to southwest to the Sacramento River. Figure 1 shows the contours of equal hydraulic head at the site and the general'rzcd direction ofundwater flow as determined b l� y �. DWR staff based on water levels call. -wed from production wells on the M & T Ranch. be downward There seems to a very small gradient from the upper unconfined sand and gravel aquifer at the site and the lower confined aquifer_ Based on water levels at the site .and information 4provided by 13M, Little Chico Creek -'recharges the groundwater at the site. The rates of groundwater flow were calculated from estimates of hydraulic 1 conductivity and. groundwater hydraulic gradients for the -site (Department of Water Resources, 1993). The average regional hydraulic gradient is about. 3-5 feet per mile. This value for the hydraulic gradient is consistent with data presented in Hull (1984) for the water table and It was therefore assumed to apply to the shallow unconfine4 aquifer as well as the deep confined aquifer at the site. The hydmulle conductivity of the shallow and deep sand and gravel layers was assumed to be about 400 feet per day based on aquifer tests conducted by DWR- Using Darcy's law which describes the groundwater velocity as equal to the hydraulic conductivity, K, multiplied by the hydraulic gradient and dividedby a porosity of .35 (Freeze and Cherry, 1979), the velocity of groundwater flow in the upper and lower gravel and sattd layers is about 280 feet per year. The hydraulic conductivity value of l8 feet per day for the fine grained deposits was taken from Hydrologic Consultants, Inc (1996). 71 1 1 'Tile amount of groundwater recharge from creeks for the Hydrologic Consultants, Inc. model was detemtined to be about 2,000 acre-feet per year. l..ittle Chico Crede represents about 4 percent of the total inflow to the Butte Basin from creeks and was therefore assumei; to recharge abont'$tt acre4& per year to the groundwater. This amount was assumed to be distributed equally over the reach of the creek which resulted in a recharge estimate from. little Chico Creek of 12 acre-feet per year for the site. The amount of groundwater flowing out of the southern boundary of the site was calculated by difference under the, assuniption that there is no net long term change in groundwater storage for the proposed mining area. The pre - reclamation mass balance equation for groundwater at the site is j 72 D -I A Pot :n i f Imo �l ld[Ld � titer s ehc Ttrsolt ofGrty.r.1 hliuing Activ.itics . The priwry impact .on the groundwater flow regime at the'site will be due to the teati.on of tale as the result of removal of gravel_ Since gravel will be removed irfltrt 'below - the water table, the level of the lake will be contiguous with the groundwater table_ The average depth of the lake will be- about '70 feet, The oreation of the Lake will ,allow direct mpotranmpiration from the groundviratcr and enhanceouridwater recharge. charge. The changes to the groundwater flow regime and on down -gradient waterIevels were quantified by calculafmg: an annual mass balance for the proposed site. The mass balance calculations were based on available data for the area, First, a pre - reclamation groundwater mass balance for the proposed tr ining area was developed. The proposed training and processing area is abouf 5.00 acres..; This was the area used for the groundwater mass balance calculations. The iiihount afgroundwater flowing in the northern boundary of the site was calculated based on the regional hydraulic gradient and the variation in hydraulic conductivity for the different aquifer materials in -the cross section. Hydraulic conductivity values were obtained from Department of Water Resources (1993) and Hydrologic Consultants, lne:(1996). 'Recharge from precipitation was assumed to be .10 percent of the total precipitation of 22..5 inches per year or 94 acre-feet per year.Thi percentage of the precipitation that contributes to groundwater recharge is consistent with the pezcintage used for areas of similar rainfall in Xoio County (Department of Water Resources, 1994). It was assumed that the proposed site is presently not irrigated and that there is no groundwater recharge from 'irrigation. Strem recharge from Little Chico Creek was calculated from information presented in Hydrologic Consultants, Inr..(1996). 'Tile amount of groundwater recharge from creeks for the Hydrologic Consultants, Inc. model was detemtined to be about 2,000 acre-feet per year. l..ittle Chico Crede represents about 4 percent of the total inflow to the Butte Basin from creeks and was therefore assumei; to recharge abont'$tt acre4& per year to the groundwater. This amount was assumed to be distributed equally over the reach of the creek which resulted in a recharge estimate from. little Chico Creek of 12 acre-feet per year for the site. The amount of groundwater flowing out of the southern boundary of the site was calculated by difference under the, assuniption that there is no net long term change in groundwater storage for the proposed mining area. The pre - reclamation mass balance equation for groundwater at the site is j 72 D -I A Qinput - Qoutput — n — .QinflOw + Qcrech + Qprech - Qoutflow, C1) where Qin flow is the amount of groundwater flowing across the northern boundary Qcrech is the amount of creek recharge Qprech is the amount of precipitation recharge and Qoutflow is the arnount of groundwater flowing across the southern boundary. Qoutflow was calculated based on Darcy's law. Qoutflow = K(Ax)-A (2) where A is the cross -so ional ares of the groundwater system, K is the hydraulic conductivity in feedday AWAx is the hydraulic. gradient (61mge in hydraulic head in feet, Mi, divided by the distance, 4x) Figure 3 shows the groundwater mm balance for the site before mining activities. Tha mass balance changes during and with the completion of phase Imining activities. Tirst, the groundwater mass balance was estimated for conditions representative of a half=way point in tho- clamation process. The mass balance was estimated during tidning operations for a, 93 -acre .takae and evaporation of about 50,400 gallons per day (56.5 acre-feet per year) of shallow groundwater for gravel waslii_ng operations, As a point of reference, M & T Ranch pumped about 5,000 acre -fed of groundwater in 1989 (Depanmem of Water Resources, 1993). Evapomtion from the take surface and as the msuh of washing aperations was estimated fiom the average pan evaporation rate for the area of 5.65 feel per yM-.(Hydrologic Consultants lac., 1996). `fhe gravel washing operation was assumed to occur on 10 acres. For the area of the lake, all of the precipitation was assumed to recharge die groundwater. The mass balance is as foltows during misting activities. Qinput' Qoutput ' 0 T Qinflow + Qcrech + Qprech Qoutflow - Qevap (3) t 1 Li u where Qinflow is the amount of groundwater (lowing across the northern boundary Qcrech is the amount of creek recharge 1: , Qprech is the amount of precipitation recharge Qevap is the amount of water evaporated from the lake surface and from ng activities, and Qoutflow is the amount of groundwater Dowing across the southern boundary. For the mass balance calculations during ging activities, the groundwater Inflow. (Qinflow) was assumed to rami constant and the groundwater outflow (Qoutaow) was estimated to chane based on changes 'M the meas balance as the tesult of the shining Operations and reclamfton Changes in groundwater levels down -gradient of the n hung area were c4lculated based on the change in flow across the southern boundary. Mring mining ac(vitles with a 93 -acre lake, this results in a decrease in the average groundwater flux at the southern boundary of about 365 acre-feet per year and an average water level decrease of about 0.6 foot per mile. Second, the groundwater rnass balance was esti hated using equation 3, for conditions after the completion of mining a0ti4ities. Fl" -4 -shows the groundwater mass balance after completion of phase I and the creation of a.1 86 -acre lake. The calculations are based on the assumptions that 1) evaporation %Jill occur at about 5.6 feet per year on the take surface and 2) that all. of the precipitation that falls on the lake surface will contrlibute to groundwatet recharge.. Figure 4 shows that about 1049 acre-feet mer year Will evaporate from the fake and that 348 acre -ted per year will recharge the groundwater through precipitation. An additional 59 acrerfeot per year of pr*dpitation will recharge the groundwater through the unsaturated zone. There is a decrease irk the amount of groundwater that flows across the southern boundary of the proposed site relative to pre -reclamation conditions. It is estimated that this decrease in groundwater flow will result in an average decrease in the hydraulic gradient of about 1.5 feet per mile based on Darcy s law (equation. 2). TOS will be the final amount of groundwater levet change after completion of the mining activities and reclamation. This change will occur :gradually during the mining activities and reclamation. Changes in groundwater levels of this magnitude Nvill be difficult to distinguish from seasonal and annual fluctuations in groundwater levels due to pumpHiS and groundwater S D-1.6 74 1 recharge V,36ati n Furthermore, g o s. t h because the groutidwater hydraulic fluctuations caused by mining will be superseded by recharges and discharges to the groundwater system within a short distance (within 2 miles ) dawn -gradient of the lake, the changes in water levels Will not be propagated further than I mile down -gradient of the lake. AS a point of reference, these hydraulic head changes are about tate same .as those predicted by .groundwater'flow model W- Gula6ons for gravel mining in Yolo C g ounty (3irolo County, 1990. This analysis does not ae40tlnt for flood flows at the site that will be captured by tale lake and will recharge the groundwater, and which will further offrwt water level changes caused by evaration fro the laky Po m SURFACE WATER RES0If RCl+ S The primary surface water feature in the M t'* of The area to be mined is 14ttle Chleo Creek WWOh flows west from its origin through the City of Calico and flows south parallel to the Sacramento River. The area of the proposed mining itncludes parts of the off-bannel flood plain of the creek. The creek flows into Angel Slough south ofthe site. Little Chico Creek will not bo disturbed by the mining operations. Streamflow data for Little Chico Creek were obtained from the DWR in Red Bluff for stream gage A,04280 located Soo feet south of Stilson Road., 3:6 miles east of Chico. Streamflow records are available from 1958 to the present. Little Chico Crock flows intermittently and the average annual flow at the gage east of Chico is about 21,000 acre-feet per year: The gaging station is located 500 feet east of the diversion dam that -diverts water from Little Chico Creels to Butte Creek through Little Chico Creek -Butte Creek Diversion Canal dufutg high water. The diversion dam is designed to divert flows from Cattle Chico Creek to prevent flooding of the City of Chico which occurs when Mows exceed 2,200 cubic feet per second (cfs)..Based on the available data, the 50 -year And 100 -year maximus i flowsare 2,423 and 2,706 ch,,respectively. Streamflow in Little Chico Creek spills into the diversion when flows reach 850 efs. The diversion is designed to divert up to 4,500 ofs. > tgure. 5 shows the temporal variability in annual maximum strea.rnfiow and gage -- height for the period of record. Figure 6 shows the temporal variation in annual discharge. The data thow that the largest annual flow For the period of record occurred during water 6 ' D-1.7 75 1 1 1 1 1 1 i year 1984 and the second largest occurred in 1995. The peak flow of 1640 cfs and peak, gage height of 6.32 feet in 1995 is third largest for the period of record, lower than the peal; gage heights of 6.4 and 7.17 feet and flours of 1130 and 1790 ofs for 1978 and 1964, respectively. The estimated recurrence intervals for these maximum flows are 8.75, 11.7, and 35 years for 1995, 1978 and 1964, respectively. For the annual flow, the roccurrence intervals for 1983 and 1995 are 37 and 18.5 years, respectively. Aerial photos for these years were examined to evaluate flooding at the proposed gravel -mining site. 01 1_ 11 1_ i s U t 0_ I ti _ .i, it : i 1 1. 4 M .— Figure 7 is an aeAal photo taken on March 16, 1995, and provides inforotation about the extent of flooding at the site during: high water conditions representative of an approximately 9 -year recarrenc o interval. 'The photo shows water flowing across the proposed site, There are two potential oottsequences of:this flow across the site during periods of high. flow in Little Chica Creel. Fust, the lake will capture much of this now which wig contribute to groundwater recharge. Second, thq flow into the lake may affeet groundwater quality_. The extent of additional groundwater recharge during periods of high flow is impossible to accurately rst%txtaw without additional data but it is not unreasonable to assume that there could be at least several hundred. acre-feet per year of additional groundwater recharge as a result of strearriflow into the lake. The volume of available storage in the lak=e assuming a groundwater level of 10 feet below land surfaee, is about 186© acre, - feet. The potential water quality effects are discussed in the next section. WA'T'ER QUALITY Possible sources of groundwater contamination as the result of mining activities include cheo*a1s released from eguipritemt operation and wills, movement of agripultural cltelnic, is and nutneltts Into ihelake. and changes in the chemistry of recharge water as th result of in -lake processes. The lake will be a dirgi"nduit to the groundwater system. There is a potential Impart from Little Chico Creek during flood ilows. The groundwater quality can be affected by two factors as the result of flood flows that may cross the site: agricultural chemicals and nutrients. Since there is.a high sediment . load during high flow, the primary concern is contamination from constituents attached to sediment particles. Additional phosphorus associated with sediment particles that may enter 7 , 3 the like in flood flows could contribute to eutropldcation in the lake. Eutroplucation could alter the water chemistry in the lake and affect the groundwater chemistry. Specifically, the production of excessive organic matter in the lake could lead to anaerobic conditions which could lead to the mobilization of iron in the take sediments and movement of iron into the groundwatet. Data presentt<d is Bull (1984) indicate that groundwater in the area generally has low iron and manganese concentrations indicating oxidized conditions. Chenacally- reduced groundwater would be diluted by oAdized groundwater in the area in the shallow aquifer. Also, because of the relatively low permeability of the layors between the upper aquifer and lake bottom and the aquifer where most of the water is pumped it .is unlikely that tho chemically -reduced groundwater would reach the lower aquifer to the extent that it would affect the wetter quality of clown -gradient wells.. Agricultural chemicals that enter the lake could outer the groundwaiter if they. arenot . dograded or if they become mobilized from the stream-bornBecause e sediments. agricultural drainage and surface runoff are not discharged into Little Chico Creek (L;es Rerringer: M&T Ranch, personal communication, 1996), there is not currently a potential for nutrients derived from agricultural fertilizers or agricultural chemicals to move into the groundwater through the lake. Under tion -flood conditions, the take will not be affected by, nor will it affect, the flow in Little Chico Creek. There are no other known sources in the area of potential groundwater contaminants that might enter through flood flows. SUMMARY AND CONCLUSIONS Using available data for surface and groundwater in the vicinity of the proposedgravel mining site; an analysis was conducted to determine the potential effects of gravel inin'ntg operations on surface and groundwater resources. To assess the potential effects on groundwater flow and quantity at the site, the mass balance was calculated to estimate changes in the hydraulic gadient and the possible effects on water levels in down -gradient wolfs. The results of this analysis indicate that l) a lake created at the site will result in caihanced recharge from precipitation and evaporation from the shallow groundwater and 2) there will be minimal effects on down -gradient water levels as the result of reclamation of the site. The amount of the additional groundwater recharge that will be captured by the lake from flood flows from Little Chico Creek was not included in these estimates. 8 . D-1.9 n 77 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 1 1 1 Little Chico Creek is the only surface water feature in the vicinity of the proposed mining area. Surf -ace water data for the creek were analyzed and aerial :photos were examined to evaiuste the approximate frequency and extent of flooding of the area. Since floodflows from Little Chico Crtel; run through the site, they will be captured by the lake and will contribute to groundwater recharge. The potential effects on groundwater quality as the result of mining operations and recltimation ware assessed by an evaluation of the possible pathways and mechanisms for groundwater contamination. FoOlble pathways are the t tion of constituents Nub, lubdomts, etc.) assod'ated with the witting operations, movetient of nutrients and pesticides onto the site In flood flows of Litilt Chico Crock, and changes in groundwater chemistry as the, result ofia-lobe processes. Docause agricultural runoff' and drainage do not flow into Little Chico Creek; groundwater contamination as the result of flood flows at the site is highly unlikely. Because of limited nutrient input to the lako, "rophication and resultant changes in the groundwater chemistry were assessed to be highly unlikely._ The movement o€chen icaf constituents associated with the mining operations will be controlled in accordance with. State and Federal Storm Water Discharge requirements. This will prevent movement of contaminants to surface and groundwater. 9 D-1.10 78 REFERENCES Department .of Water Resources, 1993, M & T C1itCa Ranch Graurtdwater Investigation, Phase 1, Memormidrm! Report, Northern District, Red Bluff, California Department of Water Resources; 1994. State {Yater Project Cor�nrctive Else •Eastern Yofa County, Sacramento, Califon is Departtr t of dater Usaorm,1996, Water.levels for wells on the M & TRatrch, written ronumWoation, .Rei Dluil; Callfhn& Freeze, R, A. and Cherry, J.A.,1979, Groundwafcr, Prcutice-Hall, .Englewood CM, New Jerry Hydrolog' Consultants, Inc., 1996, Deuetopment of a groundwater model; Butte Basin Area, California, Davis, CC&n is Hull, J.C., 1984, Geachetrristry of the GroundWater In the Sacramento Valley, California, U.S. Geological Survey Professional Paper 1401<13, Washingto; ; D.C. Colo County, 1996, Draft Environmental Impact Report for O„ f-Chwwl Minim Play for Lower Cache Geek, Woodland, California r f hf8 T CH CO RANCH MME FIGURr +. Plan Vitro OJ Propoard n�i���.�� si(r ♦l�ow.ing c.mours of trqal grour\d—wwatr. •I—acvon aiA g5nrraliila direc iort5 of g"rp54nd-wour flow. its Giniivi i.iie al (Ibfii .sp• -'�'� 61F•CU90 �ItfU1M-SiO�R� iSdY wjA Scale in Feet low 0 420M KR:G' �:Ekic�:rI INC. 80 1_ 1 1 1 1 1 1 i 1 1 1 1 1 1 1 1 1, Land surface (120 feet above sea level) 5 -100 -2C MI..1 Distance along transect (ft.) Figure 2. Geohydrologic cross section showing general distribution of aquifer materials, directions of flow, and hydraulic conductivity values I tai F"wuc r elude Suver n mchaig. -)Li acre -A 12 acre -fl Distal m idone "mect (N) Rpre 3. Annual inputs and outputs to the groundwater systern--al the proposed site. S.Ue= nW Pred 9 recharge acre -ft Distance along transw (ft.) Figure 4. Annual inputs and outputs 16 the Proundwater system upon completion of phase I amd.a 186 -am lake. 82 L)-1.14 Ajunlml Flow in Acre Feet Per Year M .&C '04 yzg.;.cr'ht in Feet mximiam now in Cub.!,c Feet per Second. 14