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Well Installation Report March 2002

Section 2 - Well Installation Methodology

Three groundwater monitoring wells, CS-MW3-LGR, CS-MW4-LGR, and CS-MW5-LGR were drilled and completed in the Lower Glen Rose Formation. The DO23 wells were installed under the guidance and methodologies developed under the RL83 well installation workplan addenda and their revisions in the CSSA Environmental Encyclopedia. Specifically, this includes the work plan (Volume 1-11.2, Work Plans, RL83 Addendum) and the RL83 Sampling and Analysis Plan (Volume 1-3, Sampling and Analysis Plan, RL83 Addendum). This section describes the drilling methods used, geophysical logging conducted, well construction details, well development data collected, and decontamination/management of investigation-derived waste (IDW).

2.1 - Drilling of Pilot Holes and Well Boreholes

Pilot holes for wells CS-MW3-LGR, CS-MW4-LGR, and CS-MW5-LGR were air rotary cored by Geoprojects International, Inc., under supervision of a Parsons geologist. Wells CS-MW3-LGR, CS-MW4-LGR, and CS-MW5-LGR were installed at the locations indicated on Figure 1 � Well Location Map. 

Core barrels were 10 feet long. Core samples were examined, field screened for VOCs, and logged by the onsite geologist. The core samples were described using Unified Soil Classification System (USCS) terminology with respect to lithology, color using a Munsell color chart, grain-size, weathering, moisture content, plasticity, and fossil content. Other observations included indications of rock hardness and depth of driller�s breaks (intervals of more rapid drilling indicating possible vugs, fractures, or consolidated lithology). Air returns were monitored for indications of water. Selected core samples were submitted for VOC analyses. All core material was boxed, labeled, photographed, and temporarily stored at CSSA, pending transfer to the University of Texas at San Antonio Geology Department. The boreholes were advanced at 10-foot intervals.

A single shot declination tool was used to check the plumbness and straightness of the boreholes. The declination tool was run in the borehole after every 50 feet of advancement. All monitor wells are plumb within 2 degrees of vertical. After coring was completed the boreholes were drilled to depths of over 300 feet using a 6-inch diameter tri-cone drilling bit. After geophysical logging of the borehole, a 7-7/8-inch diameter bit was used to ream the boreholes to final borehole diameter for well completion. Drilling was performed using a Gardner Denver 1500 or CME 75 drill rig. A coalescing filter system that ensures air blown downhole is free of contaminants was employed during drilling operations. The drilling rigs were thoroughly steam-cleaned prior to the start of work and decontaminated between drilling of the next borehole.

Drilling for CS-MW3-LGR was initiated January 19, 2001 and completed February 1, 2001. CS-MW4-LGR was drilled from February 14, 2001 to February 16, 2001. CS-MW5-LGR was drilled from January 29, 2001 through February 1, 2001. Cuttings and drilling generated during the drilling process were collected and stored in on-site rolloff containers for testing. Depending on the soil analytical results obtained, soils generated were properly disposed of. Continuous coring of each pilot hole was conducted. 

2.2 - Monitoring Well Construction

All wells were constructed using 4.5-inch schedule 80 PVC riser and 25-feet of 304 stainless steel continuous wrap screen. The diameter of each well was 4 inches and the screen slot size was 0.050-inch. An end cap was fitted to the base of each well screen. Well riser joints consisted of 10-foot lengths and were joined together using PVC collars and secured using stainless steel screws. No glues of any kind were used for joining the riser joints. Stainless steel centralizers were attached to well risers approximately every 50 feet to keep the well centered in the borehole. 

Silica sand consisting of an 8/16 sieve size mixture was tremied into the annular space from the base of the well screen to 2-4 feet above the top of the well screen. A hydrated bentonite chip seal 2-5 feet thick was added to the top of the sand pack. The remaining annular space from the top of the bentonite seal to just below ground surface, was pressure-grouted using a thick, pumpable slurry of water and Portland cement mixed with 5 to 7 percent bentonite powder. The slurry was placed using a tremie pipe. Well construction logs and observed lithology for each well are located in Appendix A of this report. Well depths and screened intervals are shown in Table 1.

Table 1 - Well Completion Data

2.3 - Surface Completions

Monitoring wells were completed above ground level. Well stick-ups with locking tops extend approximately 2 to 3 feet above ground surface. Bollards consisting of 4-inch diameter carbon steel in 5-foot lengths were installed around the well stick-up to provide protection to the above ground portion of the well. A two-piece aluminum locking cap was installed on each monitoring well. These caps are comprised of a ring installed on the top of the protective casing with set screws and removable cap that, when locked in place, is secured on two sides. The cap is equipped with sample ports for collection of groundwater samples and water level measurements.

A concrete pad, 5 feet by 5 feet by 4 inches thick, was constructed at the ground surface of each well. A 2-inch-diameter brass monument, permanently marked with the monitoring well identification, was set into the concrete pad. The concrete pad was finished out with a broom to create a non-slip surface. The well stick-up was painted white. Bollards/protective guard posts were installed around the monitoring wells to prevent damage from vehicular traffic.

2.4 - Monitoring Well Development

Monitoring well development of CS-MW3-LGR, CS-MW4-LGR, and CS-MW5-LGR was performed by air lifting and pumping. Immediately after well completion, loose material was removed from the wellbore by air lifting. Compressed air was injected downhole to within 20 feet of the total depth of the well via the drill pipe string. At selected intervals, the driller jetted the well by releasing bursts of air pressure in the saturated column, thus causing the sediments to become suspended and airlifted to the surface. Airlifting effectively removed most of the sediment. 

Once airlifting was completed, well development was conducted by pumping each well with a 1-horsepower Grundfos submersible pump rated at 5 gallons per minute (gpm). Approximately every 20 minutes during pumping, water temp, pH, and conductivity measurements were taken. This process continued until the water removed from the wells was clear and the readings stabilized. In all, approximately 1261, 1392, and 1623 gallons of water were removed from CS-MW3-LGR, CS-MW4-LGR, and CS-MW5-LGR during well development.

2.5 - Soil Samples

Soil and rock samples were collected in each borehole in accordance with field sampling protocols for the project. The samples, listed below, were analyzed for VOCs. None of the environmental samples showed detectable VOC analytes. One trip blank was found to contain methylene chloride at 0.0054 milligrams per kilogram (mg/kg) above the reporting limit of 0.00014 mg/kg. Analytical detections are presented in Table 2.

2.6 - Geophysical Borehole Logging

Borehole geophysical logging was performed on CSSA wells CS-MW3-LGR, CS-MW4-LGR, and CS-MW5-LGR. The logging tools used were the caliper, natural gamma, resistivity, and self-potential. These tools yielded information on borehole size changes, shale content, and formation conductivity respectively. Geo Cam of San Antonio, Texas performed the geophysical services. All logging was done in open boreholes. All tools and the entire cable length were decontaminated with a high-pressure steam cleaner prior to logging each borehole. Direct readouts were obtained on site during the logging process. Results of the logging were then used to determine the depth, thickness, and geophysical characteristics of water bearing zones. In addition, information on lithology and stratigraphy was obtained from the borehole geophysical data. The borehole geophysical logs for each of the wells can be found in Appendix B.

The geophysical data will be evaluated in detail under the RL83 assessment of the hydrogeologic conceptual site model at CSSA. In general, the caliper, SP, and resistivity data helped locate the best intervals for packer tests. The gamma logs defined the top of the Bexar Shale as approximately 427 feet bgl (902 feet MSL) in Well CS-MW3-LGR, 325 feet bgl (881 feet MSL) in CS-MW4-LGR, and 448 feet bgl (887 feet MSL) in CS-MW5-LGR.

2.7 - Injection Packer Tests

Packer tests were performed on each of the new boreholes before they were completed as monitoring wells. Using the core samples and geophysical log data, lithologic intervals were tested for hydrogeological characteristics. Each selected interval was isolated with straddle packers and injected with groundwater from CS-9, one of the on-post water supply wells. The groundwater was injected at a constant pressure. Volumes injected ranged from 0.7 to 22 gallons. Data collected included elapsed time, injection volume, and pressure. The field measurements were used to estimate hydraulic conductivity of the tested intervals. In several intervals the test was stopped when results showed that the formation was not taking water at that interval. A brief summary of the results are listed in Table 3, and the packer test data for each well, along with the water loss and flow readings, are contained in Appendix C.

Table 3 - Packer Test Results

2.8 - Well Surveying

All CSSA wells were surveyed for top of casing and natural ground (NG) elevations, as well as northing and easting coordinates. The NG elevation was measured by the surveyor as the approximate median ground elevation of a well upon a topographically sloped surface. A licensed surveyor provided surveying data for the new wells. Fisher Engineering, Inc., performed the surveying for this project. Fisher Engineering, Inc., measured the top of casing and NG elevations for the three new monitoring wells CS-MW3-LGR, CS-MW4-LGR, and CS-MW5-LGR.

Control was brought in from the state benchmark BM1167 located near the intersection of Interstate 10 and State Highway 3351 (Ralph Fair Road). All points required to control the survey were occupied as stations within a closed and adjusted traverse. The controls meet or exceed third-order accuracy standards. 

The surveyors referenced two vertical and horizontal controls. Fisher Engineering, Inc., reported data in NAD 1983. The 2001 Fisher well survey information is shown in Table 4.

Table 4 - Well Survey Data

2.9 - Decontamination Procedures

2.9.1 - Downhole Decontamination

The drilling rig, augers, core barrel, and all downhole sampling and logging equipment were decontaminated using a high-pressure steam cleaner prior to the drilling or logging of each borehole. Core barrel samplers were further decontaminated between each use. The decontaminated equipment was stored on plastic sheeting or on racks until ready for use. The geophysical logging tool was decontaminated by hand by the subcontractor prior and following each use. Depending on the last use of the geophysical tool (water well or environmental well), the support cable was rinsed with the high-pressure steam cleaner.

2.9.2 - Decontamination of Sampling Equipment

All sampling equipment, including bailers, split spoons, trowels, and chisels were decontaminated prior to use with an Alconox^� soap scrub wash, potable water rinse, isopropyl alcohol rinse, and a final distilled water rinse. Split PVC pipe used to hold the core samples was also decontaminated in this manner. Decontaminated equipment not used immediately was allowed to air dry and then wrapped with aluminum foil for storage or transport. Teflon� bailers utilized in this project were of the pre-cleaned disposable type; therefore, the single-use samplers did not require any decontamination.

2.10 - Management of Investigation-Derived Waste

All IDW was managed in accordance with protocol outlined in Environmental Encyclopedia (Volume 1-4, Section 1, Introduction and Field Operations, Investigation-Derived Waste Handling).

For this project, IDW consisted of:

	Drilling water and cuttings from air/water rotary drilling and coring operations;
	Purge and development water;
	Water and detergents used to decontaminate field and sampling equipment;
	Personal protective equipment (PPE); and
	Miscellaneous trash associated with sampling activities (e.g., paper sacks, plastic, etc.).

Ancillary wastes such as plastic sheeting, PPE, and disposable sampling equipment were segregated from other IDW and disposed of as nonhazardous plant production waste in accordance with the EPA protocol (Investigation-Derived Wastes During Site Inspections, 1991).

All drilling water, development water, and drill cuttings removed from the boreholes during coring/drilling/development activities were temporarily contained in plastic lined roll-off containers. Samples were collected from the containers, and analyzed for VOCs. Soil cuttings were found not to be hazardous and were disposed of onsite. If drilling water VOC levels were found to be less than the respective MCL established for drinking water by the EPA and TNRCC, the water was discharged to the ground. If VOC levels were found in excess of the MCL, the water was taken to the CSSA GAC for treatment and discharge at outfall 002. In all, eight drilling water samples were collected from roll-offs associated with the installation/development of CS-MW3-LGR, CS-MW4-LGR, and CS-MW5-LGR. Only one of these samples, collected from CS-MW5-LGR roll-off, exceeded the MCL and required GAC treatment.

Two soil cutting samples were collected during installations of CS-MW3-LGR, CS-MW4-LGR, and CS-MW5-LGR, and submitted for VOC and metals analyses. The analytical results were compared to Tier 1 PCLs established for environmental site investigation and closure by the TNRCC. Based on analysis, no cuttings samples exceeded the respective PCLs and the cutting were taken to an on-post �borrow pit� for disposal.

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