Hydrological and Geochemical Characteristics in the Edwards and Trinity Hydrostratigraphic Units Using Multiport Monitor Wells in the Balcones Fault Zone, Hays County, Central Texas Alan Andrews, Brian Hunt, Brian Smith Purpose Rising-falling K Slug-in K Slug-out K Zone Zone (ft/day) (ft/day) (ft/day) Thickness (ft) Trans ft2/day Stratigraphy 21 0.3 -- -- 35 10 Stratigraphy General Hydrologic ID To better understand the hydrogeological properties of and 20 53 -- -- 70 3700 Eagle Ford/ Hydrostratigraphy Function thickness in feet Lithology Porosity/Permeability Sources Rising-falling K Slug K Zone Transmissivity Qal? confining Zone (ft/day) (ft/day) Thickness (ft) (ft2/day) 19 5 8 6 30 140 40-50 Dense limestone Buda unit (CU) Low 18 3 3 -- 25 84 relationships between the geologic units that make up the Confining Units 14 -- -- 136 -- CU Blue-green to 17 38 -- 44 105 4000 Upper Del Rio 50-60 Upper Confining Unit 13 65 -- 72 13000 137.9’ Fract oyster wakestone yellow-brown clay 16 29 80 19 70 2000 12 2 -- 34 460 145.7’ stylolites and fract I Edwards, Upper and Middle Trinity Aquifers and to compare Georgetown Fm. CU Marly limestone; grnst Low 15 29 105 161 75 2100 40-60 11 4 -- 159 8300 Crystalline limestone; mdst to wkst 14 8 10 3 45 370 Leached and 199.6’ fossil (toucasid) vug Aquifer (AQ) III to milliolid grnst; chert; collapse High 10 0.09 -- 197 50 13 4 2 6 40 160 observed hydrologic properties of formations to generally accept- Collapsed mbrs 230’ solutioned bedding plane 30-80 breccia 9 0.005 -- 97 4 12 0.2 -- -- 85 -- 200 feet Reg. Dense mbr CU IV 20-30 238’ solutioned fracture Low; vertical barrier Argillaceous mudstone 8 0.7 -- 56 515 11 0.1 -- -- 90 -- Person Person Fm. Grainstone mbr AQ V 45-60 Low ed understanding of them and suggest nomenclature that best 283’ solutioned fracture Milliolid grnst; mdst to wkst; chert 7 26 -- 68 21000 10 0.2 -- -- 100 24 6 0.4 0.9 72 365 9 0.6 0.1 -- 30 16 Kirschberg AQ VI Crystalline limestone; chalky High mbr 5 -- 0.2 77 -- 8 0.4 -- -- 30 -- describes hydrogeologic properties of hydrostratigraphic units 65-75 mudstone; chert 1996 et al., Small 4 -- 37 27 38000 Edwards Aquifer Edwards 7 0.3 -- -- 70 -- Edwards Group Edwards 3 26 -- 26 27000 6 0.1 0.6 -- 70 6 4d. in the study area. 4c. 4e. 4f. 2 34 -- 20 36000 5 0.202 -- -- 40 8 VII Mudstone to grainstone; Locally permeable Dolomitic AQ 1 -- -- 41 -- 4 6 7 7 30 170 Kainer Fm. mbr 110-150 crystalline limestone; chert Figures 4a-f. Tool used to open and close Introduction Table 1. 3 0.2 -- -- 30 5 2 1 1.5 2 25 26 Basal Nod- Karst AQ; VIII Shaly, fossiliferous, 1 19 60 -- 55 1060 nodular limestone; mudstone Low ports inside wells. Ports consist of a screened section • Permeabilities are a dening characteristic of aquifers. ular mbr not karst CU 45-60 Table 2. Karst and fract Interval A Alt. mdst, wkst, and pkst permeable near Edwards AQ not karst CU 30-120 local solution zones contact, decreases with of PVC coupling, which when moved up or • Detailed permeability data for distinct depth Tables 1 and 2. List distribution of hydraulic conducti- CU; AQ assoc. Interval B Alt. mdst, clays, wkst Low Karst and fract 120-150 and pkst down, respectively open or close the casing to forma- litho/hydrostratigraphic units in the Edwards and Trinity Upper Figure 4a. 4b. vities in Ruby Ranch (left) and Antioch (right) multiport wells, Lower Cretaceous Lower Upper Member Trinity AQ Interval C Calcareous mud and Moderate; breccia, and moldic 10-20 ft vuggy mudstone (boxwork) texture tion water. Aquifers has not been quantied in a single borehole. Glen Rose based on rising/falling head tests and slug tests. Limestone Alt wkst, pkst, marl; AQ assoc. Interval D High in biostrome; lower 90 ft thick biostromes • Hydrologic connection between hydrostratigraphic units in this biostromes only 135-180 very low porosity locally Moderate breccia, Hydraulic conductivity values for the three hydrostratigraphic Calcareous mud and AQ Interval E and moldic (boxwork) area is not entirely understood and needs more thorough char- vuggy mudstone 7-10 texture Clark, 2004 Clark, AQ in bioherms Lower Glen Rose (Clark, 2004): Good porosity and perm. groupings observed are: 320-340 acterization to better manage water resources. and evaporite beds, Alt mdst, wkst, pkst, and grnst; in bioherms; low porosity and Lower Member karst and fracture; bioherms permeability elsewhere CU elswhere • Edwards Aquifer, values between 0.3 and 66 ft/day. Glen Rose • Two Westbay multiport wells were used to measure Middle Lower Glen Rose (Wierman et al., 2010) Fabric selective; AQ in reefs ~250 Limestone Trinity Alternating mdst, wkst, and grnst; Good porosity and 26 ft/day avg. lower and upper reef intervals permeability hydrogeologic characteristics of rock units. in reefs Hensel CU 15-40 Low • Upper Trinity Aquitard, from 0.01 to 0.7 ft/day. Mudstone, clay and shale Location 2010 Wierman et al., AQ ~70 Figure 5a. Figure 5b. Cow Creek Grainstone, dolomitic toward base High 0.25 ft/day avg. AUSTI N Co l d Hammett CU ~40 Low; permeable near top Bar ton Confining Unit Mudstone, dolomite, and clay Figures 5a,b. Examples of underdamped and overdamped Barton Creek Sp r ings Figure 3. • Middle Trinity Aquifer, from 0.2 to 37 ft/day. Sp r ings water level equilibration. Bouwer-Rice (Fig.5a) and Butler (5b) analy- Williamson Creek Methods 13.6 ft/day avg. Hwy 290 tical solutions were used to calculate hydraulic conductivities at IH-35 Two Westbay multiport wells were used to measure water Conclusions ContributingTravis County Zone HaysHa County each port, based on water level response. ys County Recharge Zone levels, conduct rising/falling head and slug tests, and • Observed hydraulic conductivities of the various formations Figures 1 and 2. Antioch Westbay Well Hydrostratigraphy Elevation (ft-msl) vs Depth (ft) TDS K that make up the Edwards Aquifer (Fig. 3) generally agree with BearCreek collect water samples at ports located at dierent depths, and Results 570 590 610 630 (mg/L) (ft/d) Fm 1826 702 ft-msl D Wells are located in the Barton Buda screened individually to distinct litho/hydrostratigraphic layers. Del Rio those qualitatively assigned by previous studies. 100 5/18/11 2/16/11 12/2/10 9/30/10 Springs Segment of the Lith. Notes Gamma Caliper Ruby Ranch Westbay Well Georgetown 21 Hydrostratigraphy (cps) (in) ns 0.3 • Upper-most units of the Upper Glen Rose exhibit high hy- Zone Symbols Select Borehole Photographs Elevation (ft-msl) vs Depth (ft) TDS K Leached & 0 100 5 10 Collapsed fracture Eagle Ford/Qal? (mg/L) (ft/d) 200 20 273 53 Edwards Aquifer, within the Stratigraphy Multiport Well mbrs Buda 815 ft-msl 620 640 660 680 700 720 Saline (brackish) breccia 40 Person Little Bear RDM 19 279 4.5 draulic conductivity and good quality water similar to units in Confined Zone chert nodule Creek Del Rio Grainst 18 ns 3.3 Antioch Well Balcones Fault Zone. Both wells gypsum 80 300 5/18/11 2/18/11 12/2/10 9/30/10 ns - BUDA pyrite Figure 4. Multiport 100 Ruby Well 120 Dolomitic Kirschberg 133.5’ Oyster wake-packstone 14 17 288 38 the Edwards Aquifer. calcite spar Georgetown Fm. 21 Member mbr 160 154.2’ fracture are about 15 miles south of Austin irregular bedding Leached and f,m Kainer Formation 13 329 66 400 Onion Creek 165.4’ Caprinid rudist Edwards Group f 199.6’ fossil (toucasid) vug Edwards Aquifer laminar bedding m well layout and examples 200 Edwards Group 200 Collapsed 20 16 • Most of the Upper Trinity “Aquifer” is best described as an f 304 29 230’ solutioned bedding plane A) Solutioned fracture zone 20, Walnut Fm. 12 Dolomitic shale beds mbrs A b 263 1.6 Kainer Fm. IH-35 240 Person Fm, Edwards Grp. mbr D’ chickenwire texture Reg. Dense mbr f and 3.5 miles apart. 19 b 238’ solutioned fracture 500 rudistid Fm. Person B of downhole imagery, 300 15 280 18 1,320 (4/08) 302 29 Grainstone mbr 283’ solutioned fracture 291.2 toucasid wake-packstone aquitard and conning unit in this area, especially when shell fossil f 11 to 28 N 320 C f 289 (6/09) 14 Kirschberg b 600 Walnut Fm 446 8.3 caliper log, and 400 0 2 miles Porosity 360 17 mbr 13 439 4 comparing its hydraulic conductivities to those found in the Blanco River Group Edwards Upper Member KYLE f = fracture 400 Glen Rose m = moldic 700 12 f gamma log, which were 500 Limestone 3,567 0.1 Figure 1. b b = bedding 440 16 b 3,270 0.1 Edwards and Middle Trinity Aquifers. 10 480 Dolomitic f Upper Trinity Aquifer Depth (ft) Kainer Fm. B) Moddled texture zone 18, f 11 mbr Person Fm, Edwards Grp. used to establish 600 800 Upper Mbr 2,884 0.1 520 f Depth (feet) 15 Glen Rose • Uppermost units of the Lower Member of the Glen Rose 9 650.51655.80 560 f 3,852 0.01 Limestone Basal Nodular m D 14 placement of hydraulically 700 900 10 D’ 600 f 3,037 0.2 Ruby mbr 599.1 clasts? Limestone exhibit low hydraulic conductivity (<1 ft/d) and f 8 635.30 644.42 3,291 1.2 West 13 Multiport East 640 1.5 in dia 9 2,853 0.5 PVC coupling 800 Rudist isolated “zones” in the Lower Member 7 509 32 1000 8 Antioch 680 Reef 2,993 0.4 high TDS (2100 to 3200 mg/l), resembling values found in the Well 12 Glen Rose Multiport Depth (ft) 720 sampleport 6 7 3,268 0.3 Limestone 771 0.6 1100 spring 1100 packer multiport wells during 900 Well 760 C) Cavernous zone 17, 1100 Upper Trinity Aquitard.