HYDROGEOLOGY OF THE HICKORY SANDSTONE AQUIFER, UPPER CAMBRIAN, RILEY FORMATION, MASON AND McCULLOCH COUNTIES, TEXAS Approved: HYDROGEOLOGY OF THE HICKORY SANDSTONE AQUIFER, UPPER CAMBRIAN, RILEY FORMATION, MASON AND McCULLOCH COUNTIES, TEXAS by Curtis Wende11 Black, B.S. THESIS Presented to the Faculty of the Graduate School of The University of Texas at Austin In Partial Fulfillment of the Requirements for the Degree of MASTER OF ARTS University of Texas at Austin August, 1988 ACKNOWLEDGEMENTS I would like to thank the members of the Board of the Hickory Underground Water Conservation District for funding the study which led to this thesis. Additionally, I would like to thank the citizens of Mason, McCulloch, Concho and San Saba counties who, through appreciation of the value of their aquifer, started the District, and made this study possible. Rick lllgner, District Manager, deserves special credit for many days spent familiarizing me with the records of the District, meeting land owners within the District, and opening his home and kitchen, usually late into the night and on many occasions. Particular credit is due his patience throughout this project. The staff of the Texas Waler Commission and Texas Waler Development Board have been consistent sources of valuable aid and information throughout this study. Richard Preston, Dan Muller, Jimmy Russel, Gerald Baum, Birnie Baker, Gerald Adair, Toby Cisneros, Bill Moltz, Laverne Wiiiis all made the resources of their ~encies available during this study. The TW'DB funded analytical and radio-chemical work in this study. The students of the Ground-Waler Field Methods courses gave me more help than they mi9ht imagine. The stream 939ing effort in particular would have been impossible without their support. In every activity, from wading the pools of the San Saba looking for springs to braving rattlesnakes looking for wells to measure, they gave a first class effort. The scientists of the Bureau of Economic Geology were of great assistance during the study . Bill Mullican, and Ronit Nativ generously shared their knowlege and equipment for the carbon-14 sampling. Sam Valastro at the Balcones Radiocarbon Lab spent a tremendous amount of time sharing his understanding of this technique with me. Chris Caran always had answers. The residents who call my aquifer their home deserve special credit for opening their homes and ranches to me, even when they might not always know what I was doing with all those instruments or all those samples. Forest Armke of the Ford Ranch, Bob Bales of the Crooked Hollow Ranch, John O'Donnel, and names with memorable notes in my field book -Mark Smith and Kim Duke of Vulcan Materials, Jack Mcfarland, Wayne Spiller, Sleepy Bratton, Peanut Deans, laUgo Rettman, Spiller Boswell, Jack Edmiston -and Earl Behrens needs to appear here as well. Larry Garens, Phil White and other local radio amateurs are appreciated. Virgil Barnes, Chock Woodruff, Lynton Land and Raymond Slade deserve special credit for being assets lo the geol09ic community for the d'Jralion. Jack Sharp as my supervising professor is highly recommended. My parents are, I hope, proud of the role they played in this drama, as should be the ciaos of Hampton, Ruggles and the new Alaskans. Richard Herndon, KSFNI, and Tom Cameron, gave much needed Improvement to grammar and usage. Thank you all! The University or Texas at Austin. May. 1988 iii Abstract Hydrogeology of the Hickory Sandstone Aquifer, Upper Cambrian, Riley Formation, Mason and McCulloch Counties, Texas The Hickory Aquifer is a primary ground water source for Mason, McCulloch, Concho and San Saba counties, Texas. Significant water level declines have been recorded in the Hickory outcrop where large volumes of water are used for irrigation. AcXiltionally, municipal remands on the confined portions of the atim II mun 111 lo-ti Figure 2-J Geologlc north-south cross section or the Hickory and adjacent units N lJ1 ....... ..., -Q) Q) ....... c c ..., - Cl > Q) .... UJ f tgure 2-4 Geologic northwest-southeast cross sectIon of the Hickory and adjacent,unlts N (j\ evidence for this small-gradient system is presented in Chapter Four, where the radiocarbon age data show very Jong transit times from outcrop to subsurface for recharging waters. Other factors, each contributing to the regional hydro logic characteristics, are considered and documented in following sections. Figures 2-3 and 2-4 use a series of 7 digit numbers to identify wells. This we ll numbering system is used consistently throughout this thesis as well as in the publications of the Texas Water Commission and the Texas Water Development Board. For an explanation of the organization of the numbering system, refer to Figure 3-2 for a view of the we! I numbering grid over the study area or consult the publications of these institutions. Surface-water and ground-water interactions More than 50 measurements of discharge were made in the various surface-water courses which either cross the outcrop or cross shallow subsurface portions of the Hickory aquifer. A series of measurements were made In Tiger Creek, Katemcy Creek, Lost Creek and the San Saba River. The locations of these surface-water courses can be found in Figure 2-5. Streamflow data were collected in the course of my field H4wy. 67 North To Br11dy s-s.-ltT<... -- _ >.---­ ,j( / '-./. ..._/ II ~-_/ // \ _/ \ McCulloch County !McCulloch County J'1 / M11son County Mason County ' -,....-· --{ .-u......-·'\ SS-2 \ 1222 ,. I. r-z ·'\. . \ 87 I.-< /'.J "---\ ! 386 r / f / \ .., 1222 ~11temcy !'" !.\~K-1 «Ku • :; I ., 'l ~ Com Air / 1./ ~I-0 t z 3 4 .. ...'" .. ( ,~ ' Miles ~k .. Sc1tle Length = 6.6 Km j ..~ .= Northen / \. I "\ Hywif 67 South to 1111son Figure 2-5 Location map for streamflow measurement sites (note: streamtlow data are presented In Table 2-1) ..."" c :s u .. Q ., ., f.ft c ., V'I """'~ · 71 Te Po.t•tM l'l OJ work and by participants in the Groundwater Field Methods courses. Generally little gain or loss In streamflow was measured In the upper reaches of the smaller creeks, except for Katemcy Creek. Typically the upper reaches of interest are dry, presumably because they may be acting as recharge points. Table 2-1 presents the results of these measurements and Figure 2-5 shows the location of measurement sites. These data, while ambiguous, Indicate that upon a substantial rise after a period of low stage, as might be expected during heavy rains, these portions of the creeks may deliver signif leant quantities of water to the aquifer. I was present in the field area only once during a substantial storm. Indirect measurements, made after that event, while subject to at least 15% error, indicate that the upper-most reach of Katemcy Creek was losing water to the aqulfer. The adjacent fork, Dry Prong, was never observed to flow during any f leld work. Conversations with local ranchers indicate it flows frequently at an upstream road crossing and that it takes a major storm for water to flow to a crossing about 1 ml le downstream. These Interpretations correspond with expected hydrogeological characteristlcs. The channel of Dry Prong is relatively high, topographically, and its course lies primarily on lower Hickory outcrop. Generally, streamflow in the smaller streams remained quite constant across the middle Hickory outcrop, especially in the upper reaches. The data are somewhat varlab le because of the patchy distribution of the alluvium over which the creeks flow. Measurements were made of the gradient, cross sectional area and permeability of the alluvium, and even where the alluvium is quite thick, much higher gradients than were observed in the channel would be required to transmit significant water through tl1e alluvium. For this reason there is not expected to be appreciable error in the surface measurements due to flow within the alluvium. In the lower portions of each creek, however, the flow increased markedly as water moved from the imperfectly-confined lower Hickory Sandstone and out of the local flow system of the canyon walls into the streams. Figure 2-6 shows a photograph of the valley of the San Saba River looking west from the Highway 71 bridge. The river flows over the El lenburger L lmestone along this reach. At the eastern end of the study area where the San Saba has cut a deep valley, many flowing wells contribute to the flow of the river. A series of cross sections have been prepared across the streams In several places to demonstrate the interactions of the aqulfer and the streams (Refer to Figures 2-7, 2-8 and 2-9), Water-levels vary tremendously over the year because of heavy use of the aqult'er for agriculture, but the data show a clear trend from variable interactions ln the upper reaches, to def inlte discharge from the aquifer In the lower reaches of the San Saba River and Katemcy and Tiger Creeks. An envelope from lowest to highest values ls shown for water levels on the Katemcy Creek cross sectlon (figure 2-9). Ret'erring to this figure, the relative levels of the stream channel and aquifer are such that the creek may receive water from the formation in winter months, but the format1on may be recharged from the creek during periods of high withdrawals from the aquifer. One interesting observation of the Katemcy Creek cross sections is a tendency for water table elevations to be inversely related to topographic elevations. This tendency may be an artifact of the heavy agricultural stress on the aquifer in areas away from the creeks. Large 1rrlgatlon wells are generally found on the higher ground of the cultivated fields and not down In the stream channels. However, the apparent inverse relationship between land surface and water table certainly could result from recharge from the creeks. Nu1tl1 South A A. ltlOll · 1-100 . I lA)lJ · ::: _, "' Ul .. I: l '.>UO · -c c ­ =c"' !" ­ .,>"-I ·WO. UJ-"'... f j (}lJ . I Lllll · I I lJll ·'----------· --····· •··· ~I .. 1.. v.,11., .. ul ljl U•JH•J .;wll 1,H .; l u~utll.11 Flt.Jure 'L ~) "' ­ > _./:;------ .. -D w~ 1,.1200 Cnll lowerCn 1111.111~-----­ Precaml.Jriari 1100 Thousand feel 0 I 2 3 ---------------Cj(ll luwer I Km 1000 el " Ground Level lli!val1011 _ ___....----..-... --·--) UL:Olluu UI l:ro:.S SMC:llOll l Jnt I~ tthuwn un liuvluyu; hol.) , f"IQU(b 1-j •I= Water l eYol Flu1irc-2 -a Cross section B-l·r across the San Saba Hlver valley show Ing the relattonshlp between surface and ground water w lJI Katemcy Creek Cross Section C -C' East West Katemcy Cnelc Butn Edge Katemcy C1"9elc ' 56-06-409 56-06-616 •1=1669 I •I= 1662 Wl:l606 56-06-606 TD:300' 11:z1620 II PCal450 I ........ ..Ill l:t: ... 0 ........ r::., o,. CRc ... ;:::; >­ .... 1800 1700 16!)0 Figure 2-9 Cross section across Katemcy Creek.showing relattonshtp between surface and·ground water VJ (j\ The cross sections of the San Saba River (figures 2-7 and 2-8) are of Interest because they show two different possibi Illies for the water surface north of the San Saba River. In section A-A' on Figure 2-7, water levels on the north of the river appear at the same elevation as on the south of the river. Unfortunately, wells on the north side of the river fail to fully penetrate the Hickory aquifer, so it is impossible to determine the hydraul le head in the lower Hickory Sandstone. In section B-s· on Figure 2-8, water levels on the north side of the San Saba definitely ind1cate flow to the soutl\ back toward the San Saba. Evidence for local southward flow is also presented in Chapter Three. Some wells on the outcrop contain water which chemically resembles deep-basin water (sulfate and chloride rich). However, very little ls known about the completion depths and other detai Is of these we! Is. Because they are primarily domestic supplies, it is doubtful that they fully penetrate the lower Hickory Sandstone. The soi Is north of the San Saba River are limestone derived, thus, there is little incentive to dri I I to the lower Hickory Sandstone; shallow we! Is meets the need for domestic or livestock use. In order to determine the extent that the San Saba River acts as a regional discharge point for the Hickory aquifer, additional fully penetrating wells are needed north of the river. I believe the southward flow shown 1n Figure 2-8 to be an artifact of the shallow completion of these wells In the strongly fractured upper Hickory Sandstone just west of the northern extension of the Fredonia Fault Zone. If the wells were deeper, I expect flow would be shown to be slow wlth a very slight gradient to the north. Flow to the north may be modIf ied at present because of the l)eavy agricultural pumpage in the Voca area. This heavy pumpage, and the resulting reversal in ground-water gradlent, may explain the anomalous chemistry seen ln wells in tl)!S portion of the outcrop. The San Saba River was divided into several segments, because of its size and the length of the reach over which it is suspected to be lnteracting with the aqulfer. Each portion was chosen based on the presence of a potential zone of lnteractlon with the aquifer -100 ! i I I ... l I i - - • IS 4) s a 0 :a o. upp~: ~~•u..z.J~~1-.w.:~i81id0!!-d~::~~~;.~...ll!!!:-~~ie.lo-.:_:'°:::--___. "" Q,, 500 600 700 800 Figure 2-1 o Stratigraphic position vs. permeab111ty plotted ror two Hickory aquUer wells Note: supporting laboratory data are in Appendix 3 width, because permeability increases with the cube of values for fracture width. Sufficient width depends upon the permeability of the unfractured material, but generally, any appreciable fracture will impart an increase in bulk permeability. What ls seen in the plot of trie data In Figure 2-10 is a high and variable permeabl I ity in the upper and lower Hickory Sandstone. The middle Hickory Sandstone, by comparison, is uniformly very low in permeability. Harmonic means were not employed to avoid inappropriately overemphasizing the presence of low permeabillty samples 1n the Hickory Sandstone. Low permeabi 1 ity units within the Hickory Sandstone are almost always horizontal layers and have little influence on horizontal flow within the aquifer. I believe it is for this reason that the values shown from the laboratory permeability data of Table 2-2 diverge so from the pump test results discussed in a succeeding section. The result of this permeability contrast within the Hickory aquifer is that, although the middle Hickory Sandstone may transmit significant quantities of water, and in many settings might be considered an aqulf er, the lower Hlckory Sandstone ls Imperfectly confined wherever topped by either the middle (especially) or upper units. However, even where topped by Cap Mountain limestone, the degree of confinement may be modified by fractures permitting flow into and discharge from the underlying Hickory aquifer. Evidence for this can be seen In the outcrop, where a number of flowing wells appear to tap the lower Hickory Sandstone where It Is conf lned by the middle or upper units. Artesian conditions are not always apparent 1n the upstream portions of the outcrop primarily due to the lack of topographic relief and sparse well control. Irrigation water use The Hickory Sandstone aqu1fer Is the primary source of ground water in Mason and McCulloch counties. Irrigation use of the Hickory aquifer, in contrast to the municipal users of the sub-surface resource, is concentrated in the 158-square-mile (41,000 hectare) outcrop area. Table 2-3 shows the distribution of outcrop segments by creek basin within the 38-square-mile (9,800 hectare) portion of the Hickory outcrop considered In this study. A ten-fold increase in irrigation use of the northern portion of the Hickory aqulf er occurred during the drought period of the early 19SO's. Table 2-4 summarizes the Irrigation data discussed below. In 1984 the Soil Conservation Service estimated the area of Hickory outcrop Bai• Seheit iArn (sa. mi1n>i Are9 (ecr~) ~ bu Uait ~ 1Cate111eu Creek! U1oer lttckera : 1.75 1120 11.2 !1'1iMl1• tffcten! 7.71 4934 49.6 ; Laver tffctera : 6.08 3891 39.Z Total 15.54 9945 41 Tioer Creek ' Unner Hicken i 4.25 2720 23.4 :tti.,le Hickani 7.28 4659 40.2 :Lttnr Hicken i 6.6 4224 36.4 Tatel 18.13 11603 48 ~ ! ! ' Lest Creet iU••r Htctan ! 0.26 166 6.3 !1'1illll1 Hicteni 1.9 1216 46.2 ;lever tffctere i 1.95 j 1248 47.5 ' T1tal 4.11 2630 11 .ombined Total: ' 37.78 24179 100 Maxi mum total 'Yater available 'With no lo" to Eva~ration, Runeff Tra~oiration = ' 48358 Acre ft. Table 2-3 Outcrop areas by creek basin within the study area . !E.!::~~-!.~. ~.~. 2.~.~.~.~.!::Y....~.~.~.~.~t!J... ?.~.~·~·~·~·~·~·~....~.9.~.i..f..~E.!.....~. ~.~.4........... l.............................................................. L........................ ............ !McCulloch Co. ! ! Acres : Acre Feet :::::~::::::~:=::::::::::::::::::::1::::::::::::::.:::::::::::::::::::::::::1~:~~:L:::t.j:9:~:r.:~¢.:f.~:~:~::::q·r,:~:f~:~·9:~:~::::::::::::::::::1::::::::::::::::::::::::~·~:~t.:$:::::::::::~:::::::::::I:~::::::::~:::::::::::::::::::::::::::: .............--.....................L........................... ...........l.~.~.~.~-~.~.Y....~T.~.~.~.................................. ..............................l..........................?...1.. ~.........................L...................................... -~-~.~-~9.~...~.r.:~.P.....~.~.~.~-~.~....~..~.:.?..~....~... ~.P.P..~.~·~'\~....~..~T.i.9.~.~.~.~-~....1..~.... ~..~-~.~. +.............. ......1 .r.:.~~.9~.!.~..~~...=...f...........?..~.§.~........... ~~: :~~::~~r~~~-n:~:~a::_::i~r~:f~~~~~~~~-i~~i= :-_:-~-~-::1 ~ ~I~~~--: : T:::· ::~: ............. .-.....................l............................... ........:.~.~.~.!...~.r.:~.~-~....~.~.~.~-~.............................. ..... ..................l..........................~ .'J..2..........................1........................................ A.Y.~-~.9.~...~.r.:yP... .~.~-~-~-~.~...~.?.:.~.~.~....~PP.!. ~. ~.~... ~T.!::~.9.~.!.~..~-~...~.~.... ~..~-~.4.......f......................1 1'.:.~~.9.~.!.~..~~...=...............?..~.~.~............ :::::::::::::~:=:::::::::::::::::::::r:::::::::::::::::::::::::::::::::::::::II?~:4.:::(~T~:LTf.:d9:~:n:~:~:::t.:~:~:::~:!:~:ij:!i::::~~f.~:~::I~:~:f.~::::r.:~:~IL~::::::r:::::::I:~:§.$.):::::::::: ! 1984 totol lrriqotion for study oreo (cu. meters)= : 16100000 TABLE 2-4 Irrigation pumpage data ~ CJ) 47 irrigated by sprinkler (inside the study area) at 2584 acres ( 1046 hectares) in Mason county and 2593 acres (I 049 hectares) in McCulloch county. The Soil Conservation Service estimated the 1980 pumpage at 26,000 acre-feet (af) (3.2x107 m3) and predicted substantial increases over the next 15 years inside the study area using 27.85 inches (71 cm) of irrigation applied to the average crop. Similarly, for McCulloch county using 13.72 inches (35 cm) for the average crop yields 5366 af (6.6x 106 m3). Other than minor differences in reported crop selection, there is no apparent reason for the differences reported in irrigation. Annual effective recharge was estimated by the Soil Conservation Service at 31,000 to 35,000 af (3.8xlo7 m3 to 4.3xlo7 m3). It is clear that this value includes acreage outside the study area for this report. I estimated 6 inches ( 15 cm) out of the 24 inches (61 cm) of rainfall as effective recharge. This estimate is based on several contributing observations. First, the values developed by Ed Reed and Associates< 1972, 1975, and 1980) in studies for the City of San Angelo estimated values substantially lower than my estimate. The value developed by Ed Reed and Associates fails to supply suff icent water even for present-day agricultural usage on the outcrop if contributions from recharge in stream channels are not added. With the exception of the upper-most reaches of Katemcy Creek, from my work on the streams, I feel the streams contribute little water to the aquifer. Secondly1 aquifer recharge from rainfall should be significantly more than occurs on the Precambrian basement or surrounding carbonates. The estimated 6 inches ( 15 cm) out of the 24 inches (61cm) of rainfall seems conservative in light of the average slope of the outcrop of the Hickory Sandstone1 its permeability1 and the lack of clay mineral or clay size fraction weathering products. The estimated 6 inches ( 15 cm) of recharge across the 24 thousand acre (9800 hectare) outcrop area yields 12,000 af (L5x107 m3) of ground water available within the study area, a value which compares favorably with observed levels of aquifer use when observed declining in water levels are considered. Municipal water use Municipal pumpage and rural-water district water-use data are summarized in Table 2-5. Users of Hickory ground water include the cities of Brady and Lohn1 and rural water-supply corporations In Mi Jlersview-Doole in McCulloch county and the North San Saba Water Supply Corporation in San Saba county. The city of Eden in Concho county uses ground water from the Point Peak member of the Wi lberns Formation which is mixed 1: I with shallow we! I water to lower tl1e ~:~"!:~·~;~i~:~:~:;-·;r~ii·;-i~;ii;_~~~i~=J~:-=-~~-~1~1-~~iii.~i~~:-=:=J:==_:-~=. 1 MGD 1 l l -.·.·.·.·_·_-_·_·_·_·_·_·_-_-_·_·_-_·_·_·_·_:·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.·.-.·.·.·.·.·.·.·.·.:·.·.·.·.·.·.1·.·.·.·.·.·.·.·.·.·.·.·.·.:·.:·.-.·.·.·.-.·.·.·.·.-.·.·.·_·_-_-_·.·.·.·.-.·.·.·.·.·.·.:·.-.·.·.·.·.·.·.·.·.-.·.·.·.·.·.·.·.·.·.1·.·.·.·.·.·.:·.·.·.·.·.·.·.·.·.·.·.·.·.-.·.·.·.·.·.·.·.·.·.·.·.·.·.·.T.·.·.·.·.·.·.·_·_-_-_-_-_·_·_·.·.·.·.·.-.·.·.·.·.·.-.·.·.·_·.-.·.·.·.·.·.·.·.·.-.·.·.·.·.·.·.·.T·.·.·.·_·_-_-_-_-_-_·_·.-.·.·.·.·.-.·.·.-.·.·.·.·.·. Eden l 0.36 l 1210 12 800 in Concho Co. _J:!~!!:ItltII~J::-=~:-=:1i~fj~f;~=~¥/~1iil:l_=t!lllt.ti.~fJ.it~ii!~~ Lohn ; 0.02 l l8 300 in McCulloch Co. ·····································································································································································•····"······································································· MillersvieY Doole l 0.5 l l8 300 in McCulloch Co . ............................................................(;·························..·······································•············--·····················-:.....1....................................................................... ........................................................ ...~ ...................................................................L...................................1.. .......... ... .........-. ...........1.. ........................ ...............~.!.~--~-~g~~-~...............l............. ...............~.:.~..........._.............. l......-~-~.!..~.J.........L?.~."-Q.Q.Q).~..I.~.~---~r~~-~--~-~-=-··· .............. ~~-~---~-~.9.~J~...............~.?..J.. ~-~-~. P.r.~J~~~-~-~-.J~r..~~~J...f.~.~~-~---~-~-~v~~-~-P..~~-~-!.......................l..... ................ ............................................................1.. ................................. ......... ......... ..... 1............-......................L................................................L.......................... San Saba ~ 5 l 2492 15 300 in San Saba Co_ ............................................................:...................................................................:..........................................A..........................................,,•.•.•.•••...•....•.•••.•... ............................................................l~j-~~-~-~f.9.~--~-~.TQ.~9.~--~-~~i.~.~~~..fr.~.~..t'.U.U..P.~.~-~--~.r.~~-~--~P..~~--~9.~.............l....................... . ................................... ...........-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-...-+~-~-~~~..~~..~-~....~..~~-:..~~-~:..~....~....~!..~~..:...t~·:.-~..~~..~--~..~-~~:..~r....~-~=-~-~~~--~~-·::::::.-~:.-.-.-.-.-.-J.-.-:::.·:::::.-:::::::::::::.· ~P.P..~~-~J~.~~.t.~. Y.{.~.!.t1.~-~~~-~{.~~-~..f.~~-~--!·~-~-~!~.~E.QY..?.~.~~-~~~-~-~.J~.--~-~.Q..:. .......l.... ........................ ............ :. l.............~.:.?..~. .~.P.Pr~~~--~!.~~~--:~~-~.t!~.r-~'v!~Jf. r.r.Q.~!..~~~..!J.t~~r.~.Y..~-~~.t~.~rJ.t~~J.~.~J..~9..~-r--A~9.~~-~-)...I.~..n9..Q...:....,..........?..4::.?..~ .................................................................................................................................................................................................................................................. (Data from HUGWCD # 1, 1980 Texas Al ma nae and Texas Health Department) i Table 2-5 Municipal and rural water district pumpage lJl total dissolved sol ids CTDS) and temperature from the city's 4000foot<1300 m) wel I ). Additionally, the city of San Angelo is ultimately planning to pump 21 ml I lion gallons of Hickory ground water per day (8.0x 1o4 meters3/day). Nine 12-inch (30cm) diameter wells have been drilled with a total capacity of 6 million gallons per day (2.3x 1o4 m3/day). The system orlginally Included plans for 29 wells on I mile spacings, each averaging about 500 gpm (2725 m3/day). This revised municipal water use Is also summarized in Table 2-5. Climatic data Data discussed in this section was obtained from the National Weather Service (NWS) through the Texas Natural Resources Information System ~ 4> ..,i 1616 s &Id ~ 1614 ..... 0 R 0 1612 ., &Id ~ 4> 1610 iii 1608 LTI .i:. 1 55 • particularly significant, considering the annual rainfall over the same period was above average every year except 1977. Although the effective recharge on the outcrop is estimated at 6 Inches ( IScm) per year, recharge varies both areally and temporally as a function of ralnfal I, temperature, slope, and ground-cover. An individual recharge event is shown in Figure 2-13 from water level data from the TDWR delineation well number 56-06-614. The response of the aquifer is nearly instantaneous in this well, which is approximately 3000 feet (900 m) from the outcrop. Deviations from a uniform response are attributed to the intense irrigation pumpage taking place during this July and August recording period. Aquifer characteristics Table 2-6, is a summary of over 30 aquifer tests in the Hickory aquifer. Recent pump tests indicate the Hickory aquifer has a mean transmissivity of 16,340 gallons per day (gpd) per foot (62 m2/ctay or 7.2 x I o-4 m2/s). The coefficient of storage averages 0.00023 from recent tests by Ed Reed anti Associates ( 1975 ami 1980) in the San .~_um.m~.r..1J_9.f...~~!!Jf.~r::.~~-LQ!!.!l!.!Lt~.~._!Ji.f..~~r..\L~'l.Yt.f.e..L.'.. _____....•........ _. ____ .____________--; ' ' . ·r-h·~-·rr.)·~r·G8mo~n~~;·,~~ !~~~"GDf11]·u·;:;,Jt;)-Q~e\~·~,-QQ M 0 IJ Ed R~~no A~.······----·· ···--·­ :07-j.Ee~0"t!J.oi sa.!!..~9eio 6u_rTn.g o -2~~iloui-Jl!!mite;t";----·----··------------------1 • '.h.~~.. ~-'.~.~~!e.d 6 , ..ells 01 trie 9 or~mly 1n the San AOQeio Well Field • ·;i -12 inch diameter ·•ells. 3 in McCuilocn Co untu and 1 in Me08rd Co. :• :fr~.0.3-fiii:s.~'Vltu ,,,,.G!_~_~fromi 2·3·4a.P.i_l.f!. to 6~.,'?21 apd/ft.\vllh the ~~jl = 16.340 aD. "'o -f( / level surface (feet M~U I 6 mil" (JO kml r ,15"8 NORTH water 1e·1e! catum Figure 2-14 Potentiometric surface map -Hickory aquifer I. structural complexity of the system, 2. time spanned by the data, 3. lack of data from the deeper portions of the aqulfer, 4. we! Is which partially penetrate the Hickory Sandstone 5. data from areas with vertical components of flow, and 6. heavy pumpage from the aquifer. The steep dip of trre Hickory Sandstone shown ln Figure 2-3 and 2-4, markedly contrasts with the riearly rlat potentiomet.ric surr"ace fr om the outcrop to the presumed discharge point of the aquifer under the Colorado River north of McCulloch county. This implies that either the aquifer has an exceptionally large hydraulic conductivity, so that the flow dissipates little potential from the outcrop to the deep subsurface, or the water ls flowing very slowly. Furthermore, because the hydraulic conductivity of the Hickory aquifer has been measured frequently, we can solve for the transit t ime in a flow system with this gradient and known poroslty. This calculatlon ls presented ln Table 2-7. The flow rate for the aquifer segment between the San Saba River and the Clty of Lohn municipal water well is 3.2 feet per year (0.982 TABLE 2-7 Calculation of time of trnel for infiltrating ground water to reoch Lohn from the nearest wells on the San Saba River: Pertinent equations are: O=-KIA, Darcy's Law where Q= flow in feet3 /day. meters3 /second I( =hydraulic conductivity In feet/day or meters/s i = hydraulic gradient of the potentlometrlc surface, feet/foot A =area in square feet or square meters T=Kb, definition of Transmissivity where T =Transmissivity of the unit in gallons/day/foot or meters2/day b =thickness of the unit transmitting water. feet or meters I( = hydraulic conductivity, as above v =QI A = -K I, definition of specific discharge, all units defined above V a vi+ .. average linear velocity of water within the porous media, v = specific discharge as defined above +2 porosity as volumeyoids/volumetotal Values for this problem: T = 16,340 gallons/day/foot, mean value from Table 2-6 + = 22.4S from Table 2-2 42"/132,000" from San Saba River to Lohn Well (Figure 2-3) = 0.000318 = 3. 18x 1 o-4 dimensionless gradient b 350 feet, from Figure 2-10 (mean of 2 Hickory wells in figure) K 46.7 gpd/ft2 (using b, as above)= 2.2ox10-5 m/s v = -K t = -2.20x 10-5 m/s x -3.18x 10-4 = 7.0ox10-9 mis = 0.22 m/year (specmc discharge) V = vi+ average linear velocity= 0.22m/year/.224 = 0. 962 m/yeur ground water velocity Travel time = distance I velocity = 4.02x 1 o4 meters I O.982 m/year = 40, 900 years to flow from the San Saba to Lohn m/year). A travel time of 41,000 years results from using typical values presented in other parts of this chapter. Examination or the cross sections shown in figures 2-3 and 2-4 provide possible explanations for the smal I gradient. The Hickory aquifer is confined so well between the underlying Precambrian crystalline basement and the nearly vertical mi le of overlylng Paieozoic carbonates that siani f icant down-tiip discharae is l irn ited to v v that which can percolate slowly upward to eventually discharge into the Colorado River. The change in water levels across the aquifer and the carbon-14 ages recorded for ground water both support this view of the Hickory aquifer as being relatively stagnant. Chapter Three discusses other lines of evidence supporting the suggested flow system of the Hickory aquifer whlle isotopic data are discussed in Chapter Four. The carbon-14 data suggest that the flow from the outcrop to the Lohn municipal we! I takes at least 30,000 years. There are a number of possible explanations for this discrepancy. Probably most significant is that the gradient measured from the 64 I outcrop to the municipal wells, such as at Brady, tends to follow an equal-potential 11ne. That Is, flow Is moving through the cross-section at an angle nearly perpendicular to the plane of the cross section. Other factors affecting the calculated transit time Include possible error In the values measured for K from the pump-tests, deviations from the measured effective porosity, and changes in the gradient across tr1e outcrop. Additionally, faults between the outcrop and subsurface rnay impede flow outside or t11e relatively small zone lnfluenced and measured by the aquifer tests. Erosional down-cutting of the outcrop, changes in the discharges of the Colorado and San Saba Rivers, and climatic changes in the area during the Pleistocene are other possible factors. Whichever events are responsible, indications are that Hickory ground water ts not taking a direct route to the subsurface. The considerations above, plus data elsewhere in this document have been used in the development of the flow system inferred by the contouring of Figure 2-14 and 2-15. Summary of Hickory aquifer hydrogeology and recharge enhancement Ground water within the Hickory aquifer is significantly older than would be expected from the high measured hydraul ic conductivity shown in Table 2-6 of this chapter. This is caused by the effective confinement of the Hickory Sandstone by the underly1ng basement and overlying carbonates. If this overlying seal is broken by the installation of pumping wells, recharge could reacr1 the deep portions of the aquifer in a fraction of the time it takes under natural conditions. This supposition is borne out by calculations of the travel time for recharging ground water, g!ven a gradient equal to tile average d!p ( 1.5 _0 degrees) of the Hickory Sandstone. A gradient of 1.64x 10 L results from using the 31 mile (50 km) distance from the outcrop to Lohn and the 2690 foot (820 m) difference in elevation of the Hickory Sandstone from the outcrop to its depth under Lohn (see Figure 2-3). The gradient is not, of course, uniform from the outcrop to the subsurface, due to the increasing cross-sectional area available for flow radially outward from the outcrop to depth, but, using the simple assumptions above, the resulting travel time from the outcrop to Lohn (using the gradient of J.64x I o-2) results in a velocity of 50.8 meters per year or a travel time of a little over 980 years for the 31 mile (50 km) distance. This decrease by a factor of 50 in the time necessary for recharging ground water to reach the deeper portions of the aquifer Is the maximum that might be imagined and, as observed above, cannot actually be achieved. Despite these factors, nearly I 000 years is an substantial length of time for the district or users of the water to wait for effects from recharge enhancement activities. Data in Chapter Four indicate that the municipalities utilizing Hickory ground water are pumping Pleistocene ground water, but that they are not necessarily mining the ground water. The calculations above I llustrat.e the potential for more rapid flow within the conf lned portions of the Hickory aquifer. Any utilization which significantly draws down U1e aquHer will lncreJse pumping costs t'or all users, may lead to the Influx of saline waters, and should be very carefully considered, but within certain limits, water will be more rapidly recharged from updip than is normal. Another interesting calculation is to determine the cross sectional area of the down-dip surface of the recharge zone and then apply the structural gradient developed above to this area and develop the flux of ground water across this surface. One problem with this can be seen In examining Figure 2-J3. This potentiometric surface map shows a signlf leant portion of the outcrop ls isolated by faulting; ground water flows parallel to the western outcrop boundary rather than across It. However, this observation may be partially compensated for by additional water recharging west and south of the structures bounding the western flank of the Voca Anticline. Using the equations and values of Table 2-7, with the addition of 97,000 feet (29.6 km) of outcrop boundary, 350 foot ( 107 m) thickness and the gradient determined above (1.64x10-2) yields only 26 million gallons per day (1.14 m3/s or 9.87x107 m3/day) or 29 thousand af per year crossing into the confined portions of the aquifer. This value compares favorably with values calculated based on the areas presented in Table 2-3 for the available area for recharge. Under closer examination, this value is found to be far greater than that which may be delivered to the Hickory aquifer. Referring again to the Figure 2-13, the potentiometric surface map, the cross-sectional area available for supplying the subsurface portions of the Hickory aquifer is seen to be severely limited. Water can reach the subsurface only through the nose of the Voca anticline and a few breaches in the western-bounding faults. Coupled with the structural limitation on gradient, this may severely limit sustained, large-volume pumpage from the confined portions of the Hickory aquifer. The role of other less direct recharge zones (for example, the Streeter area to the west of Mason) may be significant in recharging deep, confined portions of the aquifer. However, any waters using this long, small-gradient path could not supply wells at the rates currently being discussed by municipalities in the confined portion of the aquifer. Using the total outcrop area of 24, 179 acres ( 10,000 hectares), and mean annual rainfall of 24 inches (61 cm) yields a maximum of 48,000 af (59x I 06 m3) of potential recharge from the outcrop area. The higher value does not consider losses to evaporation, runoff, surface withdrawals, or transpiration. A value closer to 12,000 af ( 1Sx1 o6m3) is probably more nearly correct. However, the contribution of recharge areas further to the south and faults to the west, as inferred in the contouring of the potentiometric surface in Figure 2-14, is not included in this cross-sectional calculation and, as discussed above, will add to the water available. The distribution of wells in outcrop areas is not designed to dewater the aquifer along the down-dip boundary of the outcrop. Because of this, it is unlikely that irrigation users could lower the water-level surface sufficiently to prevent subsurface recharge. If they should accomplish this, even temporarily, the system would recover quickly, probably annually, during the winter. Similarly, the users of the confined portion of the aquifer appear unlikely to affect users in the unconfined portion. Drawdown in the confined portion would be very substantial before drawdown could propagate to the outcrop and significantly decrease hydraulic head values there. Pumping rates necessary to achieve such a drawdown appear greater than the present utilization rates of approximately 5 MGD ( 1.9x 1o4 meters3 /day). However, the anticipated level of approximately 25 MGD (9.Sx Io4 meters3/day) is approaching the maximum yield of the aquifer determined in the calculations as developed above. For a better knowledge of the actual magnitude of this yield, much more would need to be known about the hydrologic effect of the faults bounding the western edge of the Hickory Sandstone outcrop. Ed Reed and Associates< 1972, 1975, 1980), in studies for the City of San Angelo, determined in modeling the San Angelo well field that 20 year pumping levels at the center of the well field could drop water levels nearly I 000 feet (305m). Effects could be expected to intersect contributions from the San Saba River and the faults west of the outcrop area within 1 oo years. Base flow to the San Saba and its tributaries would be significantly affected well before water levels on the outcrop. Further discussion of the effects of aqulf er use and the potential effectiveness of recharge enhancement structures on the outcrop can be found in Chapter Five. Chapter 3 Ground-water chemistry of the Hickory Sandstone Figure 3-1 Photograph of carbonate encrusted pipe discharging Hickory ground water from a flowing well near the San Saba River 70 General observations: A flowing well which was sampled for determination of time since inf i Jtration using carbon-14 is shown In Figure 3-1. Iron and carbonate encrustations color the discharge pipe. The water discharging from this pipe fell as precipitation on the Hickory Sandstone outcrop a minimum of 15,000 years ago. In the Intervening time, its chemical composition has changed markedly. The chemical composition of rainwater falling on the Hickory outcrop ls well known and unlikely areally to vary significantly over the study area (Junge and Werby, 1958; Whitehead and Feth, 1964). Its composition is affected by such factors as aerosol salt particles from the Gulf of Mexico or Gulf of California, and, more significantly, by slit and clay-sized particles blown from evaporite-bearing basins ln west and northwest Texas during weather associated with the passage of cold fronts across the region. In the present day the quartzarenite mineralogy of the lower Hickory Sandstone substantially llmlts ion exchange or porous-media dissolution lnteractlons with the aquifer. D1str1but1on of var1ous 1on1c constituents 1n Hickory water Figure 3-2 presents the location of wells for which chemical analyses were available. This map shows the state well-numbering system grid overlaying the Hickory outcrop and the locations of the cities of Lohn, Brady, Fredonia, Camp Alr, Voca, Streeter and the Millersvlew-Doole and North San Saba supply wel ls. Also included are 1.ve l l numbers corresponding to the Texas ',N'ater Development Board test holes. Table 3-1 shows the concentration of various dissolved constituents in the Hickory ground water as milligrams per liter for approximately eighty wells within the study area for which analyses are available. Table 3-2 shows these same data presented as milllequivalents per liter. A charge balance has been performed for each analysis to aid in evaluating the quality of the analytical data Figures 3-3 to 3-11 show the study area with the Ionic constituents plotted In map v1ew. The values of TDS, calcium, magnesium, sodium, tron, sulfate, chloride, nitrate and bicarbonate are plotted as Figures 3-3 through Figure 3-11, respectively. A discussion, by ion, of each of the ionic constituents fol lows. 46 I 01 ..rt• Se• Selle wmr / s.,,1, c.r,. Citll ef s-s-.----­ --...... (',o_.. '\ «) 'O. 56 .IOI,202 \ ~ 0 - In c::: ~ 0 ... l'O u l'O c ... -l'O ~ en -c c:::­ -l'O ;4-r~.£ 1> u '\_ .c. c-E In 4> en ! .c. In ... ~i c:l'I In c: ­ 'i: -;; ~ 1> - t: '­QJ ::i ­ i::: ­ =g. QJ l'O 1> >­ '­ QJ 0 ..... l'O u ..... -~ I.fl :i: N I t"l QJ '­ ::i OI - u.. I.. CJ .... ~ ~ "C c :::> 0 r... Cll t· 0 ~ u :t: c :J') 0 ..... .._ 0 c 0 ..... :::> C/) .&:;; CJ I.. ~ ...., E ;!? l'OI 0 ell I'") I I'") GJ '­ :::> en I.I.. TDS U. S. EPA Sec. DWS =l soomg/1 41,l~tive vtl.s llieve ~.eli•i•tM fn• areas •f •••-•t at1 '­ ., " l'l:l ~ I "Cl c ::I 0 '­ C) >­ '­ 0 ~ u :r: c: E ::I u l'l:l u ..... 0 c: 0 ..... ::I t/') .0 C.I '-Q. ..., E ~ l'l:l O VI "t I I"') '­~ ::I C) """ ll•plihtive nl-=s bwe lleea eliai..t.W fn• 1rea sf 1119..at ..t. 47 46 4"4 48 4~ 7.0 'Magnesium (mg/1) 1 .0 ________... 2.0. :34 .0~ 55 5453 5552 • 2.0 40.0 31.0 1!.0 40.0, 6362 6460 61 S2.0 28.0 42 06 56104 05 S1.0 1312 14 '62.0 43.0 l I tf•,11c.tive •:_-1-IMrve llee• eli•1•~ fn• area efallHl6Ht •t• '­ QI .... ~ ~ I 'Cl c:: ~ 0 '­ 0\ >­ '­ 0 ::.e. u ::r: c:: E ~ (/) C1> c:: 0\ ~ IoE c:: 0 ...., ~ (/) .Q C1> '-c.. .... E ;!? ~ 0 Cf) Lf') I f"") C1> '­ ::I 0\ u.. 47 46 ~ 46 4~ Sodium (mg/1) 2660 32-4 .0~ 192.0 96.0------­ 5652 153 j54 155 ·~.o 37.~ ~.o 1~.o. I I I I~ ~ I "Cl c:: ::l 0 L. C'I ~ 0 60 I 61 <40.o 1 52 I~3.oJ 163 164 I~ ::c c:: E99.o I I ::l "Cl 0 (/) - 0 6 I c:: --20.0 I ~~-~-____ \ L...! ...;.,............ I o 42 I I I ...... '"' ·­ 34.o 56104 105 I 06 9.0 . I01 1111: · 61 .0 ::i .. -!9. ·~2.0 'Mn IQ}! l.a.o ,~~ .0 ­ 0 I/:) I t"'l ~ 1 L. ::l C'I Nort.b ~~v 1~; fl I~-I . -~ 12 I 13 '49.0 42.0 (/') ~E (o;, (/') d••liaittve val.es Mve liee• eliaiute4 fn• ems ef 1111•..•t ata ~ l I4:l 146 147 148 '0.10 Iron (mg/I) I I I I 020 <0 .02~ ____. <0.02 54 155 1565352 0 .10 0.61 l... ~ ...... ('Q ~ I 'O c: ::i 0 l... Cl l... 60 I 61 3.sa I 62 / 1 ...1 163 j64 0 I >­ ~ u :I: I c: 0 .301 a.so 0 miles 6 I I 42 I I I I 0 . 10. I u 0 lcilometers 104 .oo ! ·~7~· 1.4f0~ 4.UU 1.40 56104 105 106 I01 ' n?n i.oo IbJ1111 nn 1 Mort.la 12 113 114 0 .90 Fe U. S. EPA Sec. DWS :::l 0.3mg/1 c: 0 l... .... 0 c: 0 ...... ::i tn .Q ~ ·-­ l... 0.. t:; E · -('Q 0 tn r--. I ,..., ~ l... ::i Cl u.. ~ Sulfate (mg/I) 4:l 46 47 4'1 :l 48 46.0, 26.0 ...----~ 9.0 --­ So4= u. s. EPA Sec. DWS I= 250mg/1 4•11liPitive nl-=i lllrn lleea eli•i•t~ fn• area •f ah..•t data ' ~ 148 14~ 146 147 .0 .1 Ni trate (mg/1) <0.02 I I I ' I 0.1-----­ -+ 1.3 ­ r.. 4> .... 52 !53 j54 155 156 ~ 0.1 '0.1 ~ 0.1. I 'O c: <0.02 . I I I I I :::> 0 r.. C'I >­ r.. 0 ~ u :::c 1;c: 60 I 61 o.1 I 62 !.02J j63 164 (I:) ,_ .... c: 1.:11 I .... 0 c: 0 ...... ::> .c 0 miles 6 't: I 42 I I I 0.1 I 4.~ I 1.~ 10 I Uo.~~ kilometers to ·­ 0 56104 105 106 0.4. 1_07 26J;:j5~i~·:o ;s.: J~ 0 .0 14.0. 2 .'I 9-.ef~· 20 .0 :J~ .0 - I """ 4> r.. ::> 1 I~ 12,.0 ~ ·"·.~ti/ 1v N~rtb I r L -I 15 I 16 12 113 114 ·~.7 4. ~ t; E (I:) ',/) No3= U. S. EPA Pri . DWS I= !Omg/1 d•pOcatiw .,.1.a i.ve llee1 ell•i•~ fre• 1rus •f •••-•t data t­ o ~ u ~ c: ~ .... I'll c: 0 .Q If) L.. ~ io­u ~ ·-E .Q Cl) -If) 0 '­ c: ~ 0 .... ·-I'll _, ~ _g I ·-'-"O c: _, ::i ~., 0 ·-'­ 0 O'l I t"l 4> L.. ::i O'l u.. ¥!'! .~~'!'~!:~....... i~.~!.. ~.11/LJHl!~!...~!1!!.....J~!!...~~!.L~~lH¢.!!~::: .~1.tL.l~J9.:!.~..!!.17I~J~1:...~1!.tJ!~~-~--'Mtt.lf..!..!M!.J... I!?..~..!:!.11t!. T'-~~~--~-~~~-!!.r.~--~~-~-.°-1.?.~.~-.r.~~.!!l.t. ~Y.!H~.~1.~..~!!!t!..f''!!!!!l.P.!! ..!~!.!~..ti~Y.!..~.!!.!!..r.!!!!..f.or...!!~.i:'!i~!!.!!.. ':!.!.!'~..~.!!.~!.. !ti!! !).!:\11.!!.!..~.!!.!d.!.!!!.l!!.?.L.. ...........................1 :5. 1~1!..Y!!!!. t!.'!~i:!~.!r .l. \I.! ~r. .~(~!l~1.\1.~!.!........... .. .............................................. ..... ... ............................ ......... ......................... ..................... ...... ················-··-··-··· ....................... ............................ tlcCullvd1 Co. 42: 45·~6il'i··;04· · · · ····· ::1 a·········· ···-··········2··a············ ........."i'92.ci.. ··· ··· .......···:i7'2':a··..······ ·······-····4·6·:a· ·········· . ...i.44·a········· ······-·9:0··-··-···· ····-·0:20...... ······5·51:ci······· 42:47:·1011:;9· ... ····· 2"io.......... .............1.0....... ··· .........266:0................. 3~o.a··-··..... ·····-····47"·0····..···· ......235·a· ···· ...........iii··----· .....a·.·10...... ······ 0·i·1·:a...... 42~54::202';04· · ··57 . o......... .. ..........40"0· ·· ··· ···········31:0.......... .. ........37ii"a·····...... ··· -····50:0 .......... ..... ..2·:;·:a··...............o:'i·--··-·········a:io.... · .. . 419:a····· 42~54~762/56 ···54 ii.................. 4a·o·.... .... ·........36 .·a···........ ... ...·36::; ·a·········.. ·········· 49.o.... ...... .. .... 'i'6·a·................ iii...... ... .......~ ···.... ... ·3~·i· o...... 42~54=acfr/73....... . ··54 a.....................4.i...o........ · .......... 20:0.......... ······· ·356:0........... ············4i·:o ... ·· ....... ......i.2:0...... ············a::r···-···· ·······4:00···..··. ....i6i:o····· 42:55:202104 · · .....43a....................31 :a...........······· ··54 .o......................i7a.o........... ·· ·········02·.-ci........... ····· 40.'ii ....... .........ax·-··-···· ·· · ·-:·........ .. .·4·i·2.a······ ·42:56=·ia·i·;79··· ··········1:0··················-······2·.a············· · ·······3a9·o·.. ·············· .. ···414··0........................ 0;:0·..······· ········202.· o···..·· · ········a:'i··-··-···· ··--·····:··········· · ····94:;·:a·..···· ;;2:6·i ::so1119 · ··· ···· 5·5·0· ........ . .......52·0· ·· ··· ······ ·4iio·........ ·...·"3620·····.. · ............00··a....... · ......30·0·.................,i1······-··· ·····3'08'0...... ... 459 o..... ·42:;;2=·frii119··· . .. ·· 52_0................... . 4io ...................2io..................... isio····..·· ·· ............ 4io............ .......1·5:0.......······ ···0:2.......... ····-·1:40...... .......366.:a···· 42:62:90·2:;:;9............i.4o.. ....... ............21 a ...... · .............9·:a· ······· .. ·· ............i.660........... .............io.... ..................ii.o ...... ...........001..-. ..... ·······4·:00 ............150·0...... ·· 42:6i=6a·i·113···.. .....52.o.......... ···•··•···28 .ii............ ··········99:c;·····.... ···· ·····31-.4 :c;................. ....aia···.... ... ·.........90:0........·····-···1:~··-··-···· -·-·a:!o............. 54·6-·a· ····· .... ......................... ......1· ········.. ·· .............................. .................................. ............... ................................... ................................... ...... ......... ......... . .................................................. ············· ···-··-·" 42-63-003/73 74 .0 6 .0 22 .0 246 .0 9 .0 !0.0 3 .:5 0 .:50 294 .0 42·6!-908/94 41 o 4.0 37.0 120.0 19.0 47.0 10.I -248.0 ·:1?~.-~~::.~Ci~Tf_~··. ·.·.·.··.'.··.·.·~~)?.··.-.-,·.·_-·-_ :.·.~:.·.~·.-:.·.~~§:-.·'.·. ··_-· .··:.-.-.~.-.·.-.-:~'i.'.9.·.·_-_-_-_-.·_-_-_-..·.._._._._-_-_-_-_-_--~§~:·.9:.".~.".".".".".".": ·:::::::::::~?..§.".".".":.-.· ·::·.· ·.·:.·::::~·~·:_9:::::::.· .".".".~.-~·.-:.I.i.".~~.~-_-_-_-_ .~--~·.-.~·:;:_·_-_-_-_-_-__-_-_-..-.·_-_-_-_-~~-~:.q_-_~·.-: ~.2.:.~3..~~-1 <:>/n .. .. . ..~~g .................. ff() ...... . .......... §Q,Q.......... .... .. }~~:<:> ........................H :9........... ... .. .. §§,Q...................9.:~..............J!:!!Q .... . ......~~-~.,Q .... ~~-~~~~~11J?.3. . .. .... ?? 9. ..................~1 9...... ........ g .Q......... .. . . ~n9......... ............ ~~ 9.......... .. .. . H Q..... ............Q1......... .........::............ ..... 19.'!.-Q..... 42-64-912/73 Sc.O 80 30.0 2270 13.0 400 200 0 .20 322 .0 4z-t::3=9i4h3 · ·· i8 ii ................. 2o· · .... :ffo....... · ·51·0............ ·. .....23·0·... · · · 29 o ..... ········0:4··-········ ..........::······ ··1iia··· 42~ii:.~-~ .i:n..11D..: 1 r. ! ~.~19!TT.!~~~~;!! S.;in S~ba Co. ! I : l ! : ! Table 3-1, Continued co \.Jl Total dissolved sol1ds The concentration of total dissolved solids nos, refer to Figure 3-3) in water from the Hickory aqulfer ranged from 130.0 mg/l upward to approximately 850.0 mg/I. In the outcrop, some values were higher than expected. These anomalously high values In the outcrop are difficult to attribute to evaporative concentration In this area of 24 incl1es (6Jcrn) or annual rainfall. Rather, these concentrat Ions are attributed to U'le actlve appl !catlon of f ertl 11zers on the outcrop. There &e two areas of highest concentration. The first ls the southern extension of the Katemcy Creek basin. Concentrations decrease as flow progresses northward across the outcrop, aga1n signaling tl1e localized, transient nature of this disturbance. The second area ls the far eastern Ilmb of the Voca antlcllne. Values In these two outcrop areas exceed the concentrations measured In the confined portions of the aquifer near Brady, and even as deep as the municipal wel I at Lohn. The highest values occur In the deep portions of the Hickory aquifer ln quadrangles 42-47 and 42-56 as well as the deep Hickory well used by the North San Saba Water Supply Corporation southwest of well 56-07-221 >was observed to produce staining water with a marked sulfide odor for the first 48 hours after not being used for months. On the second day of pumping, this odor gradually decreased untll lt was no longer detectable. Wells on the eastern faulted limb of the Voca antl_cllne show the highest concentrations of Iron Cup to 17.00 mg/1) on the outcrop. Iron concentrations in the intermediate zone rnrady) are nearly as varied as those on the outcrop. However, lower-zone wells In the deepest portions of the aquifer (and those showing high sodium and chloride values) are consistently very low In Iron (Lohn= 0.20 mg/I and below detection limits at San Saba). Sulfate Sulfate values (Figure 3-8) on the outcrop of the Hickory aqulfer are highly variable. The values range from 6.0 mg/I to 74.0 mg/I, although the northeast corner of the outcrop where the higher values are recorded may be influenced by water of deeper, intermediate-zone origin. The marked difference between the high values of the far southwest corner of the Katemcy Creek basin and the low values of the far eastern portion of the outcrop argue for an agricultural origin for the sulfate in the southwest corner. In the subsurface, the Chebotarev sequence, discussed at the end of this chapter, predicts a band of wells, the intermediate zone, showing sulfate as their predominant anion to be replaced deeper in the aquifer with wells showing predominantly chloride anions. The we! ls across blocks 42-52, 42-61, 42-55 and 42-56 present this type or patten when compared w1th wells ln the northern-most row of blocks (refer to Figure 3-2). The four wells in the blocks listed above average 91.3 mg/I sulfate. The three Hickory wells in the northern most row average 40.0 mg/I sulfate. This ls at the same time that the average TDS in the northern row ls 253_higher (725.0 rng/l vs. 578.0 mg/I, average). Chloride Crtlorlde values (Figure 3-9) on the outcrop vary widely from 13.0 mg/I to l 11.0 mg/l. Chloride is an e~­ '­ 0 ~ u z c VI 4> ::l (<;) > 0 .... (<;) tn '-4> 4> ­ ._. CL (<;) E ::::: ~ ::l tn VI '­ ...._ 4> 4> .... .... ~ ~ ~ 0 I .Q -0 '-c (<;) ::::i u 0 ·-'­ er. er. N I t"'l 4> I.. ::::i C7'I LL. If u :I: c Vl Q> :;:) ro > I ·0 -Vl ..... _ Q> ro c.. ._ E Q> ro ~ Vl ........ - I 0 .&: ...... Q> ro u ~ ...._ I ! -0 ro c -:;:) -0 42 I :;:) .... (/') Ol ,...., - I ,...., Q> .... :;:) Ol I u: 4746 48 ~ 14~ 1.0. Bicarbonate/Chloride Ratio 1.2 ____., I.I 1.1_ 52 153 154 1553.4 , l5I >­ '­ O f.2 8.1 .:.&. u J: 1.7 I I I I I c:: (f) 41 :::> "' 13.3, 17.2 I I I .2 > ..... '­ 1.0. I62 11.3 .6J 163 164 I "' 60 I 61 41 "O · '­ .c. 1.9 I I u ..... 41 ..... OI .Q '­ miles 6 (o;J uI 42 I I I kilometers · 10 4 .6 . 0.9 1.6 co .2 2.1 '2.6 ..q­ 13.9, 07 9. l:'.-s1.~.o ·o.9 106 56104 105 - 11.7 . I 4 .3 ·182~ n 41 '­ ::i Cl I U. 1 A. ~ ......~..'"' I j / Iv-I Nortb 114 I L -I 15 I16 12 113 'S.I 3.0 · (f) 41 - -~ ;: (f) "'E '­ 41 ..... (o;J ~ ~ "O c: ::i 0 -'­ Cl 4'4 I 4~ 46 47 48 2 .0· Calcium/Magnesium Ratio 1.8-­ 2 . 1 1.9­ 52 153 154 o.9. 155 0 · 0 · 156 '2.1 I ~ ~ 1.6 I I I I I .:! :::i::: c:: (f) cu 60 161 ... .. I I •·•· J 6;·PJ6354 :::i ~ I~~ E~ .2 E (f) ~ cu (f) I.I I I §, c... ~~ E ~ ....... 3:E1 :::s "tJ 42 I I I 0 .3 I miles kilometers 6 ... ·u § ;;; e.u Ol 56 I 04 I05 I 06 o .9 . 01 ~ 1 2 I 1 3 I . I, 47 46 46 'I~ 14:::! 0 .1 0 .0____. Calcium/Sodium Ratio o.o. 1.2---.... 55 54 56 53 52 • 0.0 0.9 . 1.8 0 .3 1.6 • 63 62 64 61 60 42 .tl .6. 1.0 06 05 56104 1 3 .6 North 13 12 14 • 1.8 2.2 • I ,.,., 4> L. ::i O'l u. --,-------··---­ .. ~Q3-__ ··-FE!:_~----· __ 8•!•1\C!__ _!!!l!!!!i!l _ .!!!!!!!.!l!L__ 2!!:.f•nt __ . Q,Q!~!3 Q~Q~56!._ _ _____~ --. Q!__ __ _0.Q.__ _ __:._iJ__ _§ .. --· Q Q______Q..Q.______:l...§__ __ Q.Q ______O;Q._ __ --=£~.­. --.QQ ··--------. __Qc_i __ . .. _Q,Q________QL... ___ QJ ___ -· _QQ _ _ ______ ------~~'2..­. . QQ___ ---·-··-___.: !,.L_ _ __ QQ...___..Qj______ _ ! 6__ ___ Q.J__ ___Q.l__ ____ _ _..Qj_____J~--­ · ____QQ __ __0.Q._____ --~:!_ _ . __2,L ______Q_Q____ . ___o_:!_ _ ___ Q,L_ . _ _Q_O-···· _____ ....::Q£_ _ _ _Q .Q_ ------··-___.:1 2.. 1:2_______ .Q,O --·--·-· __......::}.i__ __Q~-­ -·-·--•___:Q ,§._ _ -l~~l~Y ::-~ -:1t~ _§__ -..~.J~--~-~=1~:=-~Q,L~:-.j=~-~~f_ -0 .4 0 2 -··--1-· -. ­ 0 1 0 0 0 I I I -_Q,L ____Q.Q._________ ..::Q.£. .~~ §l=~l------f------~~ ~--­ oo I I _,4 .. .Q !._ ---··· --··--··· __Q,:!_ __ lj__l ---~~---1 -n --••+---~.l ~-­ Hickory aqulfer chemical data as ml 11 lequavalents and charge balance calculations for analyses f-' N Table 3-2 Well Hum~!!: ~~:;{~~~~ 56-01-218179 56-01-219173 56-07-2.£1173 56-07-223173 56-07-225173_ 56-07-226174 56-ot-302184? 56-01-305179 56-07-405173 56-07-406173 56-01-102173 56-01-104173 56-ot-107173 56-0H 10173 McEl..,.ny Hou5e I Lohn Mllleisvlew-D 1 Brady_!~ Brady~ chld~~~ad ochele ~SC/83 Pem Glm CltyrfSiinSaba ~. SanS.WSC/7' herok1eSleakHi heroll!le ~'!b Sch 56-0£-605179 56-0£-606173 C•+ mlllea/I : t.5:; 2.9 2.9 3.2 2.6 2.0 3.9 2.1 2.6 2.0 5.8 50 g__ 4.6 2.4 0.0 1.7 1A.__ 2.5 - 2.0 ~ 5.2 0.1 3.6 4.0 3.5 2.1 56-0l-6Q~D~ ____ll__ 56-0£-6 ! ~1-74 1.2 56-0l-7QJ.L?3 45 56-0l-601e3 36 l"!i.!..!_ __~~­mll!.!!!L .-!!!!!!!'l!L ~-~ --+~--­ o.4 -1:-2 ­ o .4 ~-11-­ 0.8 --1-9 . 0.3 0.5 0.7 ---1~ 03 1.3 u ---2 :7 0 .5 1:-3 ­__o~-~2_2_ 0.6 1.9 0 .8 1.3 09 08 - --·-r--·----·--­ Q_S__ __!l__ _ ___o,L__Q~--­ ___0£__ __ __ _ _1 ~ __ _____Q_ _ ____L~ 3.9 Q!! ___ 2~-~ 0 .1 14!_ t.7 16 --f-------­ 2 2 1.2 0 6 1 1 !!fQ3-_ 501::_____ _ f !: _-.-!!!!!!!!I!! m!!!!g!L ~!!!!!!!! --H--~:~------i~ · ---,--7---04---- -o-8 ­_____i _3 __ --·o 2 ·-----10 · =-=~~-=-=---01--:. =~j :. 33 02 04 ==~~=: ---0~---~= =-i:~-~=­ ----26­ -:__-=:-21.= ___1.:2_ --· ---~:9_ -_ §_] 54 18 _----2.:§_~_ 2-0----::-= ·-45 _ 1 0 1.4 5 0 0.5 1.9 ___ =-1_ 9-­ 66___ ___ ~ 1.1_ r----E.~-§.,O li._~_.7___ LQ_ _____§..~-­ __3_.5____u ____ _6L _ 3.6 1.7 5 9 --r----­ 2.6 25 45 0.7 1J= _:=is-­ _____L§._ __?__1. _ 48 __ §.:2___ 3 .8 __ £,_1 _ 04 10 ---1-.5-------29 --­ -0.4 -= =Q_~~-:. _ o 5 ____ ! 2 _____o_.§._ ______ _____Q_! ___0,§._ _____ ) ~ --______Q,6_____ _Q_J _________f_Q__ _ _0,£______ !:~---__ __0_ 1_____Q.l_______--2..:9__ 02 10 0.1 06 40 ---~~=___ =._-=:= o 3---· ====-·----~0,1 o---= ==i,?__ 0 3 I 5 0 2 0 8 = .Q; L_ .-=----fi_:== =-=_Q.:.L= --~== =~Q_ _L_0_ n J..:._1_ o9 _ 1 3 19 --0 4-=-=---==jj __ ~--~-0 o== =--==~==: ==0,2_ __:!3 __ __----2.:.Q_ -----------___Q:l__ O,§_______ ___ ~) _____ oo_______ _----1§. _____ 1___? _ _______OQ____ -~J___ -----~_§ __ ____ .QJ!..._ __ Q;Q__ _ __:_£,§._ ____..Q.~---__ _ ________o_.1_______-J_.3_ _____Q.§._____________QL ____::.!.~ 0 8 0 0 -1.7 --------·-------- ----- ---------­ 15 00 0.0 -39 Is ----~'L-___Q?____ Q? _ __ 2J___ __ Q?___ Q.? ____ !=>_§. __ __ L? __ _ _!_§. -~5 0._7_ __ 22 0.5 19 ---- -·-···--------­ Q;~--_ ___!..:_§_ ___ 0.3 1 0 ----- ---· ·-------·-·­ 0 ~--·--!:£ __ NOL_ _ ___!!_~!______.!!!!!~.!_ !!'!J!.!!!L !!!!!!!!!!____P.!!"!!!!.L -----~J------- --·--=~-~ ··-oj-OT----·--i i ---o-o--·----0-c;------·-:06­ ==~Q,_1 --====---==-==-_ Q__!_ 03 00 -1.5 ~=~}---=--=Q:.2== ===Q~ 03 0.1 15 ---08 ___ __o_I_ _-·-> upper zone HC03-+ $04-2 >> 504-2 + HC03->> Intermediate zone so4-2 +er >> lower zone This model of large sedimentary basins can be used to divide the Hickory aquifer into three primary zones based on the degree of 110 I ground-water circulation and the dominant anions present (refer to Figure 3-2 and ground-water chemistry data in Tables 3-1 and 3-2). An upper zone is shown to exlst Jn which flow is fairly rapid and t he dominant anion is bicarbonate CHC03-). For the Hickory aquifer within the study area, bicarbonate is the domanant anion everywhere. It occurs in typical concentrations on the outcrop and with depth, concentrations increase, possibly demonstrating dissolution of the confining carbonates whicri overlie the deeper Hickory aquifer. The dominance of bicarbonate everywhere in the aquifer is a deviation from Chebotarev·s model. If deeper portions of the Hickory aquifer were tapped by wells, it is likely that sulfate and chloride ion concentrations would exceed the concentrations observed in the existing wells. An lntermedlate zone is described wl1ere flow ls slgnlflcantly Jess liynamic and sulfate is the preliomlnant anion. This zone ln the Hickory aquifer corresponds to the intermediate depths of the aquifer be.tween the outcrop and the deeper portions of the aqui fer, althol1gh ln t11e Hickory aquifer-sulfate values never appnwitr12te tl·H~ bicarbonate values (ref er to Figure 3-12). Functionally, in this work, tl1e intermediate zone ls distlngu1s11ed by those wells showing more sulfate than chloride. These wel Is are clearly visible on Figure 3-13 as a band of wel Is below U1e outcrop and above the deep subsurface w1th sulfate/chloride ratlo values greater than one. Wells within the intermediate zone include the wells surrounding Brady. From Figures 3-8, 3-9, and 3-11 1t ls apparent that while the sulfate and chloride values Increase as deeper portions of the aqulfer are sampled, the bicarbonate values also increase. Tr1e lower zone of the Chebotarev sequence ls characterized by very siugglsh ground-water flow and t1~1e presence or t1ig1~iJy soluble minerals. Higr1 total dissolved solids CTDS) and chloride concentrations characterize these we! ls 1n the Hickory aquifer. The wells along the northernmost tier of quadrangles on Figure 3-2 are included 1n this 9roup. Figure 3-2 also labels the facies and shows the approximate boundary lines between chemical facies within the Hickory aqulfer. Refer to Figures 3-3 through 3-16 to observe the lndlvldual Ionic contr1butlons whlcl1 leati to the development of these f acies in the Hickory aquit'er. Chapter 4 Radiocarbon study of Hickory ground water and radio-chemical quality Figure 4-1 Carbon-14 Sample CB-12 showing floes of barium carbonate settling within the sample jar 112 C:arllaa-14 sampll•t al t11e Blck1ry Sandstone aq11iler Figure 4-1 , shows a photograph of carbon-14 sample CB-12 sr1cwi n9 r' locs or bar iurn cart1onat~ sett.lln9 within the Jar. Tl1Js sample was collected from the domestic supply of a home 1n Voca. Figure 4-2 shows where ground-water samples were collected for radiocarbon analyses. Twelve samples, widely scattere1j across the Hickory aquifer In McCulloch, Mason, Conct10 and San Saba counties, were collected between June and September, 1986. The procedure outllne<.i In Appendix 2 was followe1j In the collect.Ion or the Hickory samples. This appendix Includes an introduction to carbon-14 sampling which may be valuable to Individuals unfamiliar with Isotopic techniques. The results of this portion of the study were previously presented at the South Central Sect.Ion of the Geological Society of America meeting (Black, 1987) Figure 4-3 shows the apparatus used in field collection of bicarbonate from Hickory ground water whi ch ultimately yielded Coneho 'LSc.•· 1111nc:lt~ _____..... ITI ~. J.ohn \._ tl Eden. a San ttille1·s ..iew Angelo l a B.oche-1 le-I Well BradJ a • field\" ll I a a ll IC eese Ran.cit C camp __ _ --~:_:~---" ~ ·',~::~~i"ft;:_M,,, ···•·•· San Saba 1----~) ) Voca \] I./(:> Outcrop 1 n _,.. •'"----,: ~ ______.......-J,il;,-. ., _.... .., . i::!.~~8 ------1camp Ai-···Z:.,..._:_/ At~~~I:t•t-t::::}"T Pontotoc San Saha 1 ll~:iso11 {:~~··"· ---T------------..J r ,;r11t . •.:) . .... Fi·c-il•)l"lta GQh,.:· F::.itr.1 t 2on.::­ Menard ~fason I Lhmo 115 ~ carbon for the carbon-14 analysis. This photograph was tak.en during collection of the Child's Ranch well sample, 56-06-201. The resultinq analytical work was completed by Sam Valastro of the U.T. Balcones Radiocarbon Lab. The del C-13 value was determined by mass spectrometer at Coastal Scientific Laboratories, Austin. The process followed to reduce the raw activity data to an isotopic age is documentecJ in the carbon-14 data reduction portion or AppendL< 2. The value used for the del C-13 value of the original soil was chosen by consulting Rightmire ( 1967), who tested arid soils from West Texas and determined a del C-13 value of -16.7°/oo. It seems probable that this value is low for the higher rainfall in this study area and it may be significantly low for the older samples ­particularly those older than 14,000 years, because of climatic and floral changes associated with the pluvial period, which ended some 10-12 thousand years ago. For these reasons, an "original soil del C-13" value of -19 °loo was assumed for all samples. This is a compromise between the evidence we have at present for a relatively arid central Texas and the values expected from the Pleistocene when the Hickory ground water presently being pumped was infiltrating the aquifer. This compromise is reasonable in light of the questionable benefit of sampling modern soil gas to determine a correction for water which recharged during the Pleistocene. 117 Table 4-1 is a summary of the level of natural radioactivity measured, the del C-13, delta C-14, and the resulting ages for each sample. Figure 4-4 is a map showing the distribution of ages determined from the C-14 activity after correction for dilution by dissolved carbonate in the aquifer or from ground-water mixing. Ca•cluians Ira• C-14 saaplint: The samples from the municipal supply well in Lohn were found to contain very little bicarbonate with large amounts of sulfate and required resampling to collect sufficient carbon to allow accurate dating. The comparatively fresh water collected at Camp San Saba on the San Saba River is relatively close to the outcrop and, surprisingly, did not contain sufficient carbon for a date (this well did not have a pump, so a pump, piping, and a 4 kW generator were set up on site). Corrected ages for all the samples ranged from less than 40 years for wells on the outcrop to 24, 100 years for the Eden well (deepest well sampled at 4000+ feet< 1200+m) ) and 28,800 years at the Lohn well. These ages represent minimum ages for the water. The water may have adsorbed a minute amount of atmospheric carbon during the sampling process. This additional radioactive carbon would bias the samples and would yield younger ages than would be measured ...~.~.~P.~'--·f............~.~.~P.~!.............1~·~·~·~!.~.!.~.~!.~...!.....l);~~.~.!.~~.¥.....1. .~~r.r.~~~.~.~... l.. ~.9.!...~.r..r.~.r. L.......~!.~t~......... ..~.~.~~!r............J.!.~.~.~~~~...................~l!.Jv.r.~>......1..~~~r.!~t!.~..i. ~.~.~.~...~.9.~.....!...(~/:..'!..~.~.)..i........~.~I~.!......... ......~·~:§}···fs~:-~i:~:::·~·:·ii; ......... ~~f~~...........J..... ..... 6·:·i·!....... ..+....·..~ri·?~·i· .. .. ..f..........:·:~..........l....·~·~·~·~·'.~~...... ........................l................Jt......................T .......................................................................... .........................:··............................................................. ......~.~.::Q~....i .....~JH.!.r.~.!.~!:'!.......,..........~§f?.!............1.......... q...?.1........... j........?9.~?..~........i..........~.~~...........i.. ...:.~.~.Ql~?....... .....£~:.9.1.....l.J.!.~.~...~~tv... ~.!.H...............~.~.~.~.~.......... J.... ... .9.:?.~.......... !.......?.~~.~~.. .... ..!........J.~.?.~.........L...:::~~.1.:.?.~....... ....S~.::Q~...............~.!.~.~.!.H.!......................~~~~~...........1....... ...9....~.~...........1........?~.~9.~....... +.........~.J~.~.........!......:.?..~.~.::?.Q...... .......... ~.~.;·~·±·...·:.t~.r.~~j·~~~~.!~;~~·...... . .................~·~·~·~·i·.·.·.·.·.·.·.·.·...J....... ..........1'..f.~.·.·.·.·.·.·...·.·J.·.·.·.··"""j·;.~J~............ J...·.·.·.·.·.·.·~:.~~~·...·.·.·.·.·.·.·.J.·...·.·.·.·;.~,~.~.·l~·............ CB-08 ! Keese Ranch 1 29131 i 0.56 ! 22862 i 947 ! -971.45 ........................................................................................................................ ................................................................................................................... ~.::Q~....i................~ ......~..~.!.l!?.................l..........~~?.?.~...........,1 .......... 9. ...1.~...........!........?~.~.9.~.......l.......J..~~.~.........i......:.?..?.QA?.?....... I ' • .....£~:J..Q..... ....~.!.r..~.~.~...~~~~!.................I f?.~~............ 1..........~.:~!...........i.........:::~.~9..........l.........~.~.~.~..........L....::~~~.&1....... t . . . .....§~:-?-1····, ~=-~~~~~:·~!!!·.. ..........J,~if3~31···········1········~1~9:0°~}········!········~·23·63'····· · ·t·····..··i·30·7·········!·.....:.~~~3~f?....... t ::_~;!t ::~~i~~=: =~itt':J_:;~~:~[;;~..:J~~~~t~1;~~V. J~~~~~o;<~~~ ::~~t~~~:~ :_:_:~.;~{;~~::: CB-02 5505 2.41 i 7.57 i 0.282 i 0.03 -962.7 -8.4 CB-09 5490 1.345 i 8.93 · ; 0.275 • 0.05 -969.2 -10.8 :::: n~a:: :::::~~1:== ::::-r~tr:-:r: :--::!~:: :: r·--rtf -: r nr :_::=i~~~E:::-:- ~l~:::::=: Table 4-1 Summary of raw data. del c-13. delta c-14 and calculated ages ...... I-' CD Concho ._.I-~ Mcfullo.-·h o: F: 1l~-"\...__.__ CB-09 2111Hib . t1 24102 a CB-0:3 CB -·fl ) 2057J 22",iOU [J a CB-02 24456 Jh1\11, 204~1 Cl CB-Ol. • . ct: -111 ""­ 1955-1 Cl;.~~~~ er·<40 CB-11 -D ,. "~'~~-·:\, ,. cemp i- j.r:.m~:· · . ,<11/·~ H1d:of" Sen.s.i;;-1:-::----------- tt.rl f:i j'•~B-12; 1 /./ ---Oukro~ ___...,., . ~ .:---<40J~-': .•·· _.-ya / >·' .~ ;7 ·- I, \ ·B-07 t-. 1 Vor•-; \' . , San Saba C --­ I'_.. } - :·, l 15315 -' -An\klit'i,,_ _.«.1::-. Pontotoc (r>----,--------' Menard Cernp Sen Seba sample appears very young but cannot be dated because the de1-C-131s positive Mason I Llano Figure 4-4 Distribution of Isotopic times since InfIltratton for Hickory ground water ~ ... ,.... ~o without atmospheric contamination. However, the samples are at least as old as reported here. Surprising results included the age determined for the rural water supply well sampled north of the City of San Saba. Its raw age was 29,518 years; however, it was significantly diluted with marine carbonate with a del C-13 of -10.5. This yielded a corrected age of 24,456 years, which was older than expected given the degree of faulting present in San Saba county and the topographic drive. Faults may provide significant barriers to the flow of water within the Hickory aquifer in San Saba county. Alternatively, the faulting may provide shallow flow paths through the fractured limestone, resulting in a significantly more stagnant flow system deep within the Hickory aquifer. One lnitial working hypothesis was that Pennsylvanian faulting cut off the Voca port ion of the rect1arge area from central t'lcCul loch county. Recharge would then enter the aqulfer In the vicinity of Pontotoc and then, because of its high topographic position, continue to flow nort11ward_, and then westward, into central t'lcCullocl1 county from the east The single age from the North San Saba Water Supply Corporation well eliminates this hypot.l1esis. The Isotopic age distribution shown In Figure 4-4 corresponds wel I to the flow system Inferred by the contouring of water level data In Figure 2-13. Flow appears to move radially out of the Voca area of the outcrop. Ages Increase rapidly from the Voca area, as the water crosses the San Saba River and enters the stagnant flow system (discussed In Chapter Two) of the confined Hickory aquifer. One unexpected result was the clustering of ages In the central portion of the study area near Brady. It Is possible that. these waters are all very olli ami that. what ls being measured ls approximately the same amount or atmospheric contamination being added to each sample. The techiques used yield detectable readings up to 38,000 years (for a 24 hour counting period) and 42,000 years (for a 48-hour countlng perlod). A 48-hour counting period was used on the oldest of these samples. The Keese Ranch (CB-08) and Bales Ranch (CB-0 I) wel Is are reversed In their expected relative ages. However, the stanliard error range is sufficiently wide to retain the traditional flow pattern. These samples are much closer In age than expected. Their ages are also closer to the value of the Eden well. T11is appears unlikely given the low hydraulic gradient and low velocity of water reaching deeper portions of the aquifer. A possible explanation for this is given below. The data from the Bales well are mildly anomalous In a 122 1 variety of ways. First, the age calculated from this well is low. Additionally, the del C-13 value of -7.5, the reported head is 80 feet higher than expected 't-> R .'l · c' 5 <: f 't/ '' :~' (') 4 ;" '1j ' {-'"'/yi:i.·."1 ,, 'P, 't 1'ypJy r....1 e~· w.....1 ....... l. an.J _,,, , ee . ye.... ir ~-.i r 1, 1 ....1111 ·v-...'lf .. , res ec. v • The average flow rate ls less than 3 feet/year ( 1m/year) within the confined Hickory aquifer. This Is calculated for flow from the recharge area near Voca to the city of Brady, approximately 11 mlles ( 18 km) to the north. Although the hlgl1 permeabl l ity of the Hickory Sandstone Is similar to that of the Carrizo, the greater confinement ylelds lower flow rates. Because ot' the clustering of ages ln the 19 to 24 tl1ousand year range, little variation with dept.ti ls exhibited In tt1e data for the Hickory flow system. The clustering of Hickory ground-water ages may be an artifact of the sample locations cr1osen. It may be that a9es do not appear to Increase more rapidly w Ith Increased depth because the samples are not oriented along a flow line, but rather nearly on a line of equal potential. Additionally, the fact that all ages are in excess of 20,000 years may reflect atmospheric contamination of waters which are substantially older and are more widely distributed in actual age. Jladio-eJtemieal signature teeltDi'fUes Tr1e Hickory aquifer has for many years been known to exhibit high gross alpr1a am1 gross beta activity. Several municipal and rural alpt1a and gross beta act iv I ty. Tr1e distinctive radiochern ical signature of Hickory ground water reflects the presence of radium isotopes. Whl le usually attributed to Jeacrdng rrorn quartz grains. tr1e ~1lstri tJut.ion or radioactivity witi'dn the Hickory aquifer may also inl11cate t'luld intlux from the urKlerlylng Precarnbrlan grani tes. A stable isotope analysis !i'.-i~i1~1....::::.:•:::.~ :.:. ·· ··. i2·;,_3 I ?~ •( ~ ! .1~•1: iJ1? lf:~.1.:_9~:::::Iif!.1-o.r: id&ii seliiwst (iii•ii'1iiuifooT4t:42: ;soi 49 .1~ ~ i 4i ;/.: 1 I•a 1 ,,_ o 2 Jg:~:iE!1~: ~EI!i----ci:: ~oi!ri~~~i~i ;jr11iii.l~~~~i~6.:1:E~~!ili!~!:~L. ' I .· -... ________ (ijijoi~;;;~·-6~fodeoii ;,!![iiei!O.i~j~c~i9'i : 31 ·•.1-6 ···is• / -5 169 • /-o.?·. · y a·_~/: jg ~-:==:===: ~O<;~eiI•-_¥.!'.st _91z i 1~~:: J :~Lfi :.::====== ~~~R~~}~~,~~j)jiTij~ill:g::~Eiqr-·-·· . =;~i~~~···!}~Ii/:?~ ..... i ~ •(: tj( ~=·:::··-~r"Q·:= ==== -· --··------··-!!!l!'!'P.!!.. ~..~!.!1!! ~~!!~ ~~ ·~~ 1' ~r.~!~ ~~~.! ~1:/:1~ ~~ ;t:~2 7( .1. ~1.~.L._. -· --------·--·----· . .. ":;; ''f~;:~ ;:I ;;:~:;::: =~=~= ~~-~!~J!fy!T!il.~~~~i0.i£i~!~iii.J·f~fi~~ I§·~z: i? .. . X~9. .·:.··.···· . , .• 1i!?~!!I···· ~-:::~.=~-----------· ~;~~~~~:~~:.~~~1~~~:!!::·~.jl .~: !.',\'~4 ~~~:!--~~~ ~'. : :~::-..... ~~~--~~:~:~== ~--~=~~ ~;~~-=-.-.·.:·····: (tlJI~'i!!!C~E9.~:~9.1!~~~i·i! A~+$ ?! 1~1~L... ·---------------· -­ ~!-.i.~~·~-~-~~-.fr-~!·_g·~.E~-~--~~Tt".·~-~ .~-~!."~.-·?.-9?. ........ -~ ? ~I . I d ~ Q .. !-~ ?! 1?.i~~·-·.· ... ···-·· ·····~·-·..-.·~·.·.·.-~..=.-~~~~.-.-~~-. ···-"· l ~~~~~~~:~:~~-~~:~-~=-~~=~~~.L--~? ~1.: ! ~j ~~!f.:~.~:·.i. ·.·::.·.· ?:(I~!==:~· ~:=-~=~==~ .. :_~.::~:~--~~--:= !;~~~::~!r!j:{~!~~:Fill ~l:~~i~J.~'H~~~~r\:~~:Y~~:;:;fi;/l~~~t_W~~;;~~N!t~~~lr~7I~::==t::::: :...:.:=:.:.. ­ Table 4-2 Current USEPA drinking water standards and Hickory radiochemical data Figures 4-5 and 4-6 show the gross alpha and gross beta activ1ties which have been mapped with radiochemical sample locations and values plotted. As can be seen, there is no apparent correspondence between the values and any particular now path or any other discernable relationship. In an attempt to determine why the data are so variable, the files at the Health Department were examined for a possible relationsl1ip between delay in sample processing and the recorded levels. No satisfactory relatlonsl-iip was found. As d\scussecJ above, trie lack or any rneaningr\11 pattern of activity with pos1t 1on along tr1e now path rnay be due to tt'1e entrance of radioactive water from below the Hickory Sandstone through deeply rooted fractures In the granitic basement. A variety of stable isotope techniques could be used to demonstrate this lf it were the case. figure 4-5 Gross alpha activity for the Hickory aquifer and overlying surface waters - Childs Well .aap A· 15 Menarct Radiochemical ttata: rjrWi'.i Al pha :JC Livi t i e'.) i n o 1i: ot: u r i e,;I I J.;J)' : ;;£' 2.6 ..,;'!"i} Voca ·~ :-:•>' San Saba .:.:.J \ · ..,,­ 11· 3.7 A :;(:L, Po ..·:::····:··' ototoc ,:-::-r--____::~ l:f'edooia ~ason I llano I-' I\.) OJ ...... N l.O Chapter 5 Summaryg conclusions and recommendations for future activities F lgure 5-I Photograph of Irrigated peanut fie ids south of Voca, Texas shortly after planting 130 Summary and conclusions Trie hy(Jrogeology of the Hickory aquifer is significantly more comp 1e> ::il ·=-l) 1"·'1"'0f"'::;tr::it.:.1j t ,.,, t'lf''.) 11' \Aj :C\ti=>t' r·.,,..,,.,.... ti' "' ~CH J J' t'0!' Tl'e.::-e . ..... , \.: \.• . -' ...Jt' I J 1...... . ...:J .... \,_. ... \.V \.J ... l I "' ...... -\.-1 ' ...., , • . I~ { 4·-i "-\.· ' I ..._l . Cr1emlcal analyses Indicate t11at, depending on location, the Hickory aquifer can be divided into three zones. Roughly following C11ebotarev's class1f lcatIon. an upper-zone, inten·nedlate zone and lower zone are !dent.if led. The lower zone includes wells hlgh Jn sotilum an<..i ct11or1de lons.; this zone is confined to t11e deepest por'tlons of the usable aquifer. Tl1ls deep, nearly stagnant system apparently dlsct'1arges tr1rougl1 tl1e overlying thickness of carbonates. ultimately to the <:o lora<..io River. H1is zone differs from C11ebotarev's classification in that bicarbonate is abundant, even tl1ougl1 sulfate anli cl1loride increase slgnHlcantly with dept!1. T11e 1nt.errned1ate zone. wl1lch Includes wells In t.r1e vlc1nlt.y of Brady, ls characterized chemically by increased sulfate and a mixture of cations. For the purpose of this Investigation, wells s1~1owlng a value greater t.11an unity on Figure 3-13 de! ineate the Intermediate zone. Tl1e comblned lower zone ancl fnt.ermNilate zone account for ne::.r'l'Y·-:.Ji o• '"l'·A c-liu'··.::·ur't".-:ic-w -.:.1' 0 ::. ,·· r' tl'e ""'.,1 Ji "0 r Pic::.r'b('\n·:.te 1··-=-c-t1·11· ...:J1 (.J I J L '"'"' ._I ._I I......, \... ( J \.. \.-J \.I ~· J \.J\.i\. I I \:= . ,_) ' . ....-J -.. I (,-J . J ..,.) I t!'1e Liorninant anl on in thi :3 zone, a~pin causing tl1e Hickory aquifer to vary from Chebotarev's model. The upoer zone featur e·:; bicarbonate water 1n an act1ve flow tJ1e Hickory Sanlistone. A small area in the northeastern portion of the outcrop on the eastern side of the Voca anticline possess Intermediate zone water cl1emlstry which ls attributed to the heavy agricultural purnpage ln trie Voca area. Catlons In the upper zone are higl1ly variable over time and posltion on t11e outcrop, controlleL1 botl1 by Intrinsic features of the aquifer and human modlf icatlons. These modifications Include significant application of fertilizers to the outcrop surt'ace of t!~e aqu1f er. the d!scl1ar9e or l1ousel1old wastewater, animal husbandry practices on the out.crop Including confined animal reeding oper'atlons, and t.11e use or rnany tons or fertll1zer-baseL1 explosives in several sand rnlnlnq operations. Isotopic age lieterrn1natlons using carbon-14 support tt'1e thesls tl1at the deep, confined portions or the aqulter are nearly stagnant. Water' within tl1e confined portion ot' the aqu1fer Is older tt1an earlier Investigations lnlilcated anli the gradients linking t11e lieep portions of the aqulf er to t.l'1e outcrop are shown to be quite low. MeasurNi times since inf I l trat ion for grounLi water present. ly In U1e conf lned portion or tt1e aqulf er ranged frorn 15,000 years to at. least 30,000 years. Rechar'9e enl1ancernent. 11as been discussed as an option for the stearn oeds wi11ct1 cro-:;s ttw outcrop. Initial plans f•.)r basins wer'e located in topographically low points ln tl1e channel system because the negat lve effects of 1nundatIon would be reduced. However, uowani motion of Hlckorv qround water unl1er these sites, as I I ~ • evidenced by now Ing we! ls, retocusNi attention to Joeat ions in topog1,apl1 Ical ly h Igher areas furtrier upstream. Cross sect l ons prepareli In tl1e course of tl1ls lnvest.l~ption Indicate tt1at 11 ttle posltlve effect from stream-course locat.eij impour'llirnents should be expected. Rather, water recharging the aquifer under an lrnpoundment. is expect.Ni to return to ttw stream course again clownstrearn of tl1e point of recharge. It is posslble for tJiese irnpounclments to de! Iver water to tt1e aquifer, but water levels must. be as low, or lower, tl1an typically occur during summer months. Also, such problems as the reservoirs t'i l Jing with granite wash after each slgnif icant storm must be addressed. Hiese observations inliicate tt'1at plans for aqu1rer development · appear to have tr1e potential for oveniran of ttw deep portions or tl'1e Hickory aquHer. Substantial purnpage) In turr\ could leali to the intr1Js1on ot' saline water anli Increased pumpage costs. While. ljlt:·;'·.~· .::.·1\ ' ·~r-r·,, •rr1 "''::'lr;:;r'1' 1'll 0i("1 ' l t)\t l t1 i'<\•ifi i"J."'· tl·'cr'·' .,,... '' (J'f'l'"'rn ·:'lbGLJt .• '• .1. J.J c .... I j :;J v\.J . l•.1 , ., .;.H. ~· "'"'-· " I "'"' UV~-•\. q..1 , . l\..f <:'. ;::. l. I .;:::; (,; I the rate or rect1arge. Recr1arge to the subsurface will be Inadequate it' limited to that flow which can pass across the nose of the Voca anticline. The combined llmitatfon of reduced aquifer cr1)ss-sect1onal area an1j tJ'1e small structural gradient of the Hickory Sandstone severely l1rnlts flow into tl1e subsurface. Additional recharge may enter from other areas. However, If the Streeter area (west of r--·1ason) Is one of tr1e areas or rechar'ge and water must move westward and then north, the system will be very slow to deliver water, being cl)aracterized by Jon~1 flow patl)S and a very low gradients. The same ls true If water must enter near Pontotoc and flow across San Saba county. None of tt1e interact ions measured between the aquHer anli tl')e surf ace-water' courses ls suH icient to rneet trie projecteti Increase in pumpage. Future 1nvest1gatlve act1v1t1es i"lucl1 of t11e uncertalnty In tl1e Jl1ove dlscuss1on would l1e reduced 1f tller'e was more a,jequate we! I coverage to t!w norU1 of the H1ckory outcrop. A.ddltional we! ls between the outcrop and Brady would 9reatly facilitate lncreaseL~ understanli1ng of U1e aqulfer. Tr1ese wells couM t1e relatively close to the outcrop to keep lirlllin9 costs to a rninlrnurn wl1lle still provldln9 1nforrnat1on about d'lernlstry and i'il';'i1•~,1'l-<.n:'.lt :.:.•' r"r·.1r~i.::.r't".:-n· ,rt•-1 ,.,.: t~1µ c:,-:if-, C:,::itv:'\ r;;V .."f' T" ·-1' t"i e:.rr~i c'::1 '1 : .1 ·,) ,~J · -..• r \i .... ........ ) d' '~"..,J I~:, J t,._, 11 \_, l•. ;. \/ I I·'·· ..._. (.J , '\..• 'i.J /(, I\ I 'It. I I t' t,_.I 1\_ ., I 1 ·\.·; informat 101\ ln partlcular, would rac1litate monitoring ttw possible Intrusion or deeper aquifer waters, it' they are actually being drawn into the Voca irrigation area. Some of these wells should be equipped w1th water-level recorders to rncnltor U:e lrnpact, it' any_, of pumpage 1n tJ1e Voca a9r1cultural area. Tl1ls data, in comtJlnatlon wit!1 al1Liltlonal chemical analyses, woulLi provide evldence for' now from the subsurface back into the Voca area. Tr1e role of the t'aults bounding the wester'n limb ot' the Voca antlcllne ls appar'ently a key ractor In t11e hyl1rornecl1anlcs of tl1e Hickory aqulf er. A pump test, or series of tests.. across the faults making up tl1e l)OllnLiary would permit evaluation ot' the effectiveness of tr1ese elements as barriers to recharge for the deep Hickory aquifer. ' 138 A major opportunity was Jost when) during the drilling of a second Clty of Eden municipal supply well, the well was not deepened to comp let lon ln the Hickory Sandstone. As Indicated ln Chapter Two, water produced from this Polnt Peak well strongly resembles Hickory ground water. There ls little reason to expect hydraullt l1ead values in tl1e Point Peak to be as high as those in the Hickory Sandstone. B~cause tJ1e !1y:jraulic conliuctivlty is less ln the Point Peak than In me Hlc:\ipc ·'.:lt' f' ( CC-t1'•r> ('IJtl'"U"LI 1"01'1()' t·e )pc-<:-( 0 ctj\! the ! \j ••) ...... ..._, .._J f... O:,J .._. I,.. I \/ v ... . ) (.J ~· .) ....} .....1 . I I ..... .} .... -1 I I IV >._J I .. } • ~· "'"'.J . J .....i ..... ' .I • d1sct1arges caiculated from tt1ese indirect means would be accurate to 15% at. best. Unless the interactions between the aquifer and the streams are very large, the accuracy obtainable by monitoring steady flow conditions is necessary to detect incremental gains and losses. Because of the value of this information to tr1e district, particularly given the importance to the agricultural users on the outcrop, the dlstict could request increased hydrologlc observation on streams In the rechar~w area or the aqulfer. Request by the Hickory Underground Water Conservation District for a speclt'ic study of this portion of the San Saba watershed would be reason&)le and coulli result in a valuable contribution to their knowlege or their aqulfer. Since the carL)on-14 study was done, anew lieep Hickory aquifer well l)as l)een completed ln Menar\.i county Wl)iCli could provilie useful inror-rnatlon as to t11e role of the Streeter portion or the recr1arge zone. No chemical data are yet available from this well. The age liatlng lione ln conJunctll'm wlt.11 tl1ls thesis coulli be useful, augmenteli by additional sampl Ing of we! Is between Brady and tl1e San Saba River. Any new deep Hickory aquifer wells should also be added as they are drl I led. This could al low us to better interpret the source of rect1arge for Hie large area of slow moving water to the north of the San Saba Rlver. Appendix 1 JU~kn:ry W.e:n Da.1a Base ( selef!ted data} 142 I-' ii::. w ...... .i:. .i:. ..... .i::. lJI ...... ~ "" ....... ii::. '3 '!!!!!.!;_ ~!!!=:] COUNI'!'__ ?_,Sm!!!=.!lu=J !!!'!'.::"!:Ll!!ev:P.fj!!ev!!H!!!! ~!P.!~ 1~!!! !!Y. ~!!! !!Y.!!! ··-Q!!!L_l _______..f.!!...'!!!!!!!!!~ ... -. it~!~iJ-~~~~~~~ -=~j~;;3~~!tiQ~ :_l=~~t~!!~.--: ~=%~~ :~~~:= _-_.'.'!l~"l ::_ ~1t1~~t -~~~~~~·~:==~--:-=~~~-~:~~: ! t2~Q.1.. --~(~(04_j__.!!!f.!nL:]OO~ lQ§~ __ _ :J!Ui~}~ M~C::~~~ L_tfr~fil~'. -1--~~fl~i~~~-=~~--j =-~1l~~~~~i~-;~~~: 1=~~~~. ­ _n~.7__ t §.t l ~tQ1 ~§ l~~l__,_ ____-·­ . ~§!320_"J _ ~§ l~~Q.!_ -l"laSOf) _____j._Q_f!g_f'lJ_f), ___ ___ l§n. ___ Q_ ___ __12 :fL.. ~?1._ __ '.PQ ·----. 21£?(Q11 ·---·· ··­~gl~30£_ MaSQ!L .• __j.Q.f)grn.!L_ __! ? t: molal bicarbonate, at an average pH of 5.6. In soil, as a result of respiration by plants and decay of organic material, tr1e partial pressure of co2 is significantly higher. Because the C-14 in this root zone was Just removed from the atmosphere, its activity is 100% of modern ( 14 decays per minute per gram). As water moves through this unsaturate·i ·he (\f)f'l/)C-J'tp uff'•'t \Atitf"> ~t \I ..........f , . , ~· ~, ..-. 11. 1 ·~., ..... ............t 1'-· ~'· \.1'...t ..f ·.... ~~.l..• .11 . v~,,._, .. .. ..J ..... \.· ! , e'...... . , I .11 . ~ tl)e addltlon of slqnif leant quantities of ratilocarbon to tl)e atrnospl1ere frorn al)ove-qrounli atornlc test.lnq ami the operation of ' - ....i=o·::.c't t ·•'c ""nl.i ·::.rreJerato....c Thi··' 1·nr· 11 1y ti;::.r"IP''t'·"r' 1ly bc)t)·'t"d ti...~ C-14' I •.\A ' .,II ~· (I I l ~-; -...._. ' . t . !1 ~·· . ' ;) J •"' ... ,. I . ,,_1 t< ' -;) .·\.· -Ill:." . content ot' the atmosphere l)y a tact.or or tr1n~e. Other variables JnclLKie tl1e periodic release of slgnlflcant quantities or "cieaLi" carl)on in t.l1e form of methane from volcanic vents. the oxidation of peat anLi coal l)y oxygenatet1grounLi water. anLi tJ'1e variable rat.es ot' ! J'::>l' 1·()I r ·:. t l ,.,,, ·:ir ,1 ·i 1·.:: <'.:° I) Il 1t 1' ·1n ('. r· i' ·:tr't'l r""4 t ,. 1''' l'l.· c tJe11 enlj; n('1 1'n I"-\.· . • ~· .\..J ·~· ...., ; I \..1 _, \.J .,_f .,,_I\. _, ..... t ! ..1 · -· i:..-J ) J f .\.I ~•. t' j u .J', .._1 ',,. . ~· . ' I I d ...) I exct1ange Isotopes with minerals Including carbonates leadlng to fractionation reactions which are d1ft'lcult to correct for. However, these latter effects seem to be minor below 65 degrees C. Due to tlw importance of the carbon-14 lsotoplc dating technique in a numtier of Lilsclpllnes.. a lar9e llterature exists regardlng corrections for the cornpllcatlons listed above c_ 13 value is used as follows to correct Uie measured activity for dilution by isotopically different cJissolve1j marine carbonate. t= 19.035x 1 o 3xlog(A stli/C-13 ori~l/ <>C-13 sarnp.>> Here are the data from the Bales Ranch Irrigation Well, CB-01, as an example of the data reduction: 2.416 grams of carbon In sample 7.58 CPM/grn. carbon for the NBS Oxalic Aclli Standard 0.281 CPM/gm. carbon for the Sample of precipitated Baco3 ±0.06 CPM/grn. carbon error for range calculation -7.5 oc-!3 value from Coastal Scient H ic Labs. Assume ac-u value tor tr1eoriginal soil was -19 per mil ..., Uncorrected age = 19.035 x IO..; log 10(7.58/0.281) = 27,238 years 7 Corrected Age = 19.035 x l 0.) log l 0(7.58/<0.281 x (-19/-7.5))) = 19)554 years For± one stanliani error ln aqes recalculate while addinq and - ~ suMractlng me error~ ln t11e act!vlty Ce~i. :t006) from t11e act1v1ty measured for tl1e sample Ceg. 0.281 In tl1ls case). Tl1ls yields an actlvlty range of 0.221 to 0.341. These calculations are well suited to a spreadsheet program. It Is particularly useful when tryin9 different val ues of aC-13onq, or when calculating the range of ages within the standard error, Carbon-14 samp1ing procedure Solution preparation BaClz solution: 400 grams of clwrnically pure BaC12 are dissolved ln 1 liter' of Liistilled water and trien filtereLi. This is essentially a saturatecJ solution and it helps to have warm water to start with as tr1e BaCl--:. cools tr1e water siqnificantlv. To conduct 2 analyses ~ -. . with "average" HC03 -composition, prepare : 300 grams In 3250 ml of water -this w iI I nt easily into a 1 gal Ion glass container. NaOH solution: Add 400 grams of reagent grade, carbonate free (fresl1 -unopeneti) NaOH to 1600 rnl of recently Lilstllleli cco,, free) ~ water. Ct.his l'eact1on ls exotherrnlc -use colli water. HilS Is enougl1 for 2 samples. Tl1ls solution ls caustlc -lf you splll lt, flu~::Ji w1tt1v1ater and a weak organic aclli ilke vlne~pr). Adli 80 ml or the Bac1 2 solution prepared above to preclpitate any carbonate present. Let settle overnight and decant (filtering Is not practical anli seerns to invite atrnospt-ieric co2 contarninatlon). Tt1ere are a variety or techniques used to collect t11e sarnp Jes. They range from acidifying the groundwater and driving off the bicarbonate as co2 gas to be collected In a sodium hydroxide filter to var lat Jons of the technique I used. They are summarized ln the realiings referenced ln the bibliography (refer particularly to A Hassan, l 982). I used the following for each sample: 1. 3 -SO liter carboys (more lf the water is low in HC03-) 2. 3 -1 quart witje -moutn mason jars for collect.1na tr1e BaCO-z . v ~ 3. An adapter w1tn a valve to connect the jar and the carboy 4. Some sort of stand to support the inverted carboy while the precipitate settles into the co llectlng jar. 5. 500 ml graduated cylinder 6. A 500 ml glass bottle to collect the C-13 sample 7. Reagent to react wiUi the sample; each 50 liter carboy needs: a. 500 m1 of Uie BaC1 2 so1ution from above b. 250 ml of the NaOH solut·ion from above 8. Misc: A hose to get the water into Hie car·boys, tape, to adapt the hose to whatever outlet is provided, a roll of teflon tape to help seal carboy lids, indicator pH paper to (Jistinguish the area between 8 -11 pH, a suppl y of vinegar to neutralize the spilled NaOH (about 500 ml/well), t1e3vy duty hand lot ion suct1 as bag ba lmJ some playtex gloves or tl)e equivalent to seal the carboy and hose t'or very slowly PlJmp1ng wells to minimize mtxlng/outgastngJ lal)els/tape anli a lab marker (Sharpie), Na2so4 or ammonium sulfate tor prec1pltatlng tt1e barium wl1en flnisl1ed. The procedure: At eac1"1 wel I to be sampled, I pos1tioned the carboys close to the ;:·• 'l'!)(i rt •:::t-.:.1'-d -.~f"l \A; ::Jc;: t h ·•r'c1l'l·11.., ly f '111•: 1·,e· !'l I f i 11 ;:.(j the· rl ........ , . •' -· v ..... , ..... ,r_"", .1 1v 1 .. • .•.} , , , .... , ........ , .J, , 1 i .._. .... 11 . graliuateci cy 111·1Lier w1tl1 250 rn I of tt1e NaOH so Jut ion and poured l t into tl1e first carboy. I tested tl1e pH of tl1e resulting solution after filling the carboy about 3;4ths full with a minimum of mixing wlth alr. From tt1e carbonate equl I lbrla curves in Garre Is and C11rist ( 1965) pH l 0 appears to be a minimum. I t1a1j no L11Hiculty act1ievlng this pH with tJ1e 250 ml ot' NaOH. After checking the pH, I aLicleli SOOrnl of Bac1 2 solution and topped ofr' tlw carboy wltt1 rorrnatlon wattir. I trien t19htly c.wpeli tJie carboy and reoeated for each of t11e 2 remaining carboys. I tt1en allowed the carboys to react and gave time for the precipitate to settle to the bottom. Dur1n9 this tlrne , I prepar'eLi the C-13 sample L)y using t!Je sarne solutlons on a smaller scale. A 500 ml L)ott.Je was r~lnseLi well wit.11 formation water. SO ml or tJ'ie NaOH solution was adcied to forrnatlon water to flll to at.out tl1ree-quarters full and mix well. Aft.er t.11e pH was t.est.eli above 10, I ali<.ie<.i 80 ml of BaCh and filled .:.... wltt1 forrnatlon water. After tt1e supernate cleareti,. I collecteli the precipitate. Fioure ~ 4-3 s1·10ws a pr1otograpi1 of tl:e sampllng ~wparatus. I posi tloned tl1e carl)oy atop tne stanli ln a st.al)Je conflgurat.lon so It dili not require t·r.:1n(J support Aclliltlonally , U'ie valve assenmiy arlli jar cart;oy preclul1el1 supporting tiw assemt1ly L1y the Jar~. I replaceli tt1e cap with tt·ie valve assembly, with t11e valve closed. T11e precipitate was collecteti In t.l'ie sample jar art.er placing tl'ie carl1oy on t11e stan<.i anli securely tJwea<.i in9 one or tt1e lal)e le<.i Jars to tlw valve. As tlw carl1oy was invert.Ni I sl1ook lt. well to Insure removing any precipitate w111c1·1 m19M have a&1ered to tl:e t)ottorn Cnow tlw top), The pr~eclpltate slowly compacted under tt1e force of 9ravity ami an.er tile boumiary bet.ween t11e precipitate ami overlying solution L1ecame vlsll)le wlt!1in tlw Jar, I closecl tlw valve ancJ rernoveti tl:e Jar. Between the valve ancl tlw Jar Jay a column ot' caustic solution. Ti1ls solution came rusl1ln9 out as the Ja1~ was removed. Gloves and eye prntectlon were used. This procedure was repeateti for eacri carboy. I avoldecl durnplng the solution on a paved surface as the Baso4 makes a persistent white stain In arid environments. My coworkers suggested adding Na2so4 to the carboy to precipitate any remaining barium, then pour out the supernatant 1iquid and co 1 lect the precipitate in a plastic bag for disposal in a dumpster. By observing Ilttle precipitate form lng after adding so4=, I concluded that most of the barium was in the precipitate previ ous ly collecte!j anli little rernainel~_:.Q_;Q?~.~ 9.~~:..~~r_1•Qr.t_a.g~j~gJ~~~CQ[>_!_~ _ J__________________________ ~:?.~~~LQ.9_?_~!?_2L~_l)_2 i!lcar~2Y.X~§_lb~L!T!!?.1Y.~!am~~~l~LC!Q_l_~J'?_~~Q~~--~[r~~ -~!~:1:;1~J~t__i fl~~r..f~-~~--a.r!9_~0~c.Jb.~-~~2.l~~--­ ~'-~ ~-~~-~-~9.g_~_Q_Q..:.1206~~-gr?m~o.L~-~rb2ri_l2J.t1~J..'!i!l~l~-------··-----·-·-----·---··--···-------· ---·-·--·_______ __J________ ···------ -----·-·--····-----··· -----· l IJ~~?..-~~_r::~-0.~~-~?.J .\:'.'.9.~_rC12_dern.~11_i_~ h__ 13_:§_s!~~!!~t~~t!g_n2f_r!Jit!...U.te{gr_~fl!~ 2.~i~t~~'.~---________J __ _ .!~l_S.__~9..E.~~io!!____ __ _2~~e_. w~_ c~~!.t~-~--·--~P.~!l~:___f_ ------~.!!!'~.9!.____ Bal es Ranch 2 .416 7 .58 0 .28 1 19554 ---~­ --· -··--·---------··-·----·-------------~-----M --------··--··•• --·--·------------------··----·-------·---------­ ·-·----~-~~~~::=~~-~;i~;-~---------~i~\6 _ ____ __. ____;~~~---·-·-·-··--·--· -----~~~-;~---·--···----1--------~~:~~---·­ ~-~r:! .. ~~-~1~.w~~ -~-=-~orr_: __________ 2:~-----__ }_!§]________ . ________Q_ :~46____ _ L-----·---~565____ -·---·-· --Mi !LE!.r.~_"!'L~~-----·i---·--2~-----____ §__23 ------________Q_:~63____J__ _____2051!_ -·· _ t1-HJ_er~-~!-~~---=-«;_or.r._'._.______ _ ______ 2 .4 ----·----~-93 ----·--______ ___'U2~-----1----2142_ 7___ -·i-~h-;~~~f~;llW~~:~-rr.-+·------~:::~-------·---~-%~------1--··-------~~~--~~ -·--+-----··---~~~~~----­ ...... ......, °' Appendix 3 TDWR Delineation Study laboratory Data 168 ! ~XA S ilATEl OtVtLOPlttW t 10Al0 ;"" ••u ••. 4.i... G3. 91' = ·'-.M~c-;..zi;_d~: ~ ~: ~ ~ ~. :.oc.1t.1:x'I:____:."?..,____::"... S.c._____, 3l ocic________ Sll.r"'f"lllT__ -___ ----_____________ -_. I t I -...!...--~­ . . 'k.,~ k~k o\, se.,. '.) ...:h ""' L.J ii.ti ·.: •• u:: J 42..-&1-..9/6 "• = .m . 0 .0 ££tfj! p <•• < 4ZW. ;NJD • ·~--­ ':!lA$ ''4A?'tl O!'l ·CLOP'lt!ltt 1041.0 ;,... -.u ••._(~_._(}!.:_~a-__ """"''---_/!1~.(~~-------­ •• :.oc•tl..oa:____:/'.:, ____:/\Sec. _____, 31QCJ;________ s'.U"""1'1_________.-----------------1 , l . 2. ~-.:.::---~---;,-{~-~------.-----------:~.:,------------------------( f --r--1-~­ __k __ ~________ /Nhd~-------------------~7r-ze~-,... • , ~-.. _________ d,o_________________ ........ __ _______ a'! _____________ 1 1 1 1 Orillor~~ _lJAw_!:e~~~B_~ff~d......__________________ _______ , _... _T_T_ 1 .. ~':.!'-·-~