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Final Well Installation Report
Section 3 - Chronological Field Narratives
To simplify presentation of the MW installations, which varied from well to well, MW construction will be presented in chronological order, with appropriate mention of deviations from the relevant Work Plan or Work Plan addenda. Further details on the Work Plans or their amendments may be found in the TO42 Work Plan and TO42 Sampling and Analysis Plan. A summary of pertinent well installation and surveying information is provided in Table 3.1.
Drilling was performed by GPI under direct supervision of Parsons geologists. Seventeen new wells were installed and eight existing wells were modified at CSSA under AFCEE TO42. GPI maintained one crew during the field event. The crew mobilized on June 24, 2002, and was equipped with a Gardner-Denver drilling rig, a 2,900-gallon water truck, a 2,900-gallon vacuum truck, a Smeal winch truck, and various support vehicles and well installation equipment. Rolloff containers for investigation-derived waste (IDW) containment were provided by Total Remediation and Excavation Technologies (TRET). Final site restoration tasks were completed on November 21, 2003.
3.1 - Upgrades and Refurbishments to Existing Wells
Fieldwork for the project began with upgrades and modifications to wells already drilled at CSSA. Five wells, CS-MW1, CS-MW2, CS-16, CS‑G, and CS‑I, were modified (Figure 2.1) under TO42. Also, one existing well, CS-H, was plugged, abandoned, and replaced; the replacement well (CS-MWH-LGR) being counted as new. Modifications to these wells began on June 25, 2002. Upgrading work continued to be addressed throughout the duration of the project. The CS‑I upgrade was the last modification, completed in September 2003. Wells CS‑9, CS-10, and CS‑11 had transducers installed as minor upgrades. Off-post private wells LS‑7 and RFR‑10 had water level probe tubes installed to aid water level monitoring. In August 2003 near the end of TO42 fieldwork, TR Drilling & Service, LLC was observed drilling a new well in the Jackson Woods subdivision for a private owner. Parsons received permission from the driller and owner to have Geo Cam geophysically log the well for CSSA. The driller also provided general well construction information. The well is designated JW-32 in the CSSA database. In all, eight existing CSSA wells and two off-post private wells were modified to some degree as part of TO42 work.
3.1.1 CS-16-LGR
Existing well CS‑16 was converted from an out-of-service Middle Trinity Aquifer supply well into an LGR well. Prior to TO42, construction consisted of 6-inch steel casing extending to 195 feet bgs and an open 8- to 9-inch diameter borehole to approximately 431 feet bgs, penetrating most of the Middle Trinity Aquifer. Upgrading at CS-16 began on June 25, 2002. The down-hole portion of upgrading was finished on July 9, 2002.
GPI backfilled the well with clean sand from the bottom up through the CC to 385.5 feet bgs. A 3.5-foot bentonite seal was placed over the sand. Grout was then injected into the section of the well still open to the BS, to 326 feet bgs. A second bentonite seal topped the grout, 326 to 314.5 feet bgs. Some sand was inadvertently deposited on top of the second bentonite seal, but most of it was airlifted out. About 4.5 feet of sand remains in the bottom of the hole. The well is open from 200 to 310 feet bgs through most of the bottom third of the LGR. Well CS-16 was redesignated CS-16-LGR.
The existing 7.5 hp submersible pump on 2‑inch pipe with electric cable was lowered into the well to 298 feet bgs. This pump will be used for future pump-and-treat pilot test operations. A 1‑inch diameter flex-pipe line was also installed to facilitate water level probe access. Parsons re-installed the existing QED low-flow pump and a transducer as well.
The original wellhead extended up from a cemented pit. The pit was filled with cinder blocks around the stickup and concreted over to form a solid pad. GPI modified the wellhead later in July 2003 by adding a 12‑inch diameter steel well cover with lockable cap. The cover is bolted onto the pad.
3.1.2 CS-MW1-LGR
CS‑MW1‑LGR was installed in 1996 and is located on level ground just north of H and I sections, near the center of the northern half of the Inner Cantonment. Upgrading CS‑MW1‑LGR included backplugging the BS portion of the open borehole from 321.5 to 313.5 feet bgs, and inserting 25 feet of 3‑inch diameter 0.050-inch wire-wound stainless steel screen. A solid PVC riser extended from the screen to inside the existing well cover, terminating at 2.5 feet above ground surface. A sand pack was placed around the screen to two feet above the top of the screen, followed by a 5‑foot bentonite seal, and then a 60‑gallon lift of grout. Surface completion was already in place from the existing well except for bollards, which were then emplaced by GPI. Major CS-MW1 work was completed on July 10, 2002, and the well was redesignated CS-MW1-LGR. Injection of additional lifts of grout continued for several days afterward, filling the annulus to ground surface. The well was developed by bailing on July 25 and by pumping on August 7, 2002. The old, cracked well pad was later replaced by GPI during work on the CS-MW1-BS and CC wells.
CS‑MW2‑LGR was also installed in 1996, and is located east of areas H and I in the northeast portion of the Inner Cantonment. The BS portion of existing CS-MW2 open-hole MW was backplugged with bentonite to 344 feet bgs on July 10, 2002, then screened and sealed the following day. Twenty-five feet of 3‑inch diameter 0.050 slotted screen was set from 343 to 318 feet bgs with a surrounding sand pack 344 to 316 feet bgs. A 6‑foot bentonite seal was put above the sand and a 50‑gallon lift of grout injected above the seal. Remaining annular space was gradually grouted to near ground surface over the next several days. The well was then redesignated CS-MW2-LGR. No additional surface completion work was required at CS‑MW2‑LGR. The well was initially developed by bailing and pumping between August 21 and 26, 2002.
Elevated pH was detected at CS‑MW2‑LGR during September 2003 on-post groundwater monitoring. The change in pH is attributable to grouting operations associated with the installation of CS-MW2‑CC in January 2003. Due to the increase in pH, Parsons directed GPI to perform additional development. The water was pumped into GPI�s vacuum truck and treated at the on-post GAC. Redevelopment continued until pH values returned to the normal range. Approximately 17,000 gallons were pumped from CS‑MW2‑LGR in September and October 2003.
This well is in the western half of the North Pasture. Well CS-G was an old agricultural well with the lower portions of a decrepit windmill tower around it. In late June 2002 GPI cleared the area and removed much of the dilapidated structure and aging sucker rods. Geo Cam geophysically logged the well in August 2002. Existing 6‑inch diameter steel casing was found to extend to a depth of 155 feet bgs, and the total well depth was 339.5 feet bgs. Surface completion was modified to incorporate an 8‑inch square lockable steel well protector. Cursory development of the well was carried out in early September 2002 and the well was redesignated CS-G-LGR. A QED pump was then installed in the relatively unimproved hole for quarterly monitoring purposes. Bollards were installed in January 2003 around the original concrete well pad.
The original well CS‑H in the northwest corner of the North Pasture was also an old agricultural well. CSSA wanted a well in the area that could supply adequate water for livestock or fire suppression, and also function as a monitoring point. The TO42 work plan called for upgrading well CS‑H, or replacement if rehabilitation became unfeasible. Attempts by GPI to remove old rusted piping from well CS‑H were unsuccessful. As per the SOW, old well CS‑H was abandoned and replaced by a new LGR well. CS‑H was pressure-grouted to the surface in accordance with State of Texas guidelines.
Coring started on August 22, 2002 for replacement well CS-MWH-LGR about 30 feet east of the abandoned well CS‑H. Work at the site was sporadically interrupted by pasture closures due to live firing exercises and inclement weather. Several days later, after attaining a cored depth of 352 feet, difficulty with removal of cuttings and infilling in the hole above the core barrel began to impede progress. The core barrel became stuck in the hole at one point. The well was reamed to 8 inches to a depth of 352 feet bgs to create a more stabilized hole for further coring operations. No drilling returns were recorded during the interim reaming below 206 feet at MWH-LGR. Coring and reaming were both completed to 382 feet bgs on September 5, 2002. Geophysical and video logs were made the next day. Logs indicated a weakly cemented bioherm between 80 and 200 feet. This material apparently contributed to the coring problems experienced earlier.
Discrete interval sampling was not conducted at CS-MWH-LGR. On September 12, 2002 the well was backplugged with bentonite to 365 feet bgs. Well design was optimized to satisfy the requirement of providing ample water for both agricultural and fire suppression needs. To this end, 50 feet of 4‑inch wire-wound screen was used. Also, 4‑inch schedule 40 casing was installed to provide sufficient inside diameter (ID) to accommodate a 5‑ hp pump and motor; development followed later. Pad and bollard installation was completed in January 2003.
GPI returned in November 2002 to bail at CS-MWH-LGR, and again in January 2003 as the water remained gritty and milky. A total of 380 gallons was bailed before the water appeared clear enough for pumping. A 5 hp pump was temporarily set at 338 feet bgs with 1.25‑inch pipe, about the middle of the screened zone. On January 23, 2003 the well was pumped at 37 gpm, discharging 2,400 gallons into GPI�s vacuum truck for transport to a rolloff pending laboratory analysis. A water sample was collected at the end of pumping, which confirmed the well was free of VOC contaminants.
In May 2003 a transducer was lowered into MWH-LGR to record water level reaction to a short-term pumping test. Data generated by the test helped to determine sustainable pumping rates and a suitable permanent pump size. Parsons conducted a 31-hour pumping test with an average rate of 39 gpm. A total of 72,579 gallons was discharged to ground surface. Analytical results of the sample collected previously indicated that MW-H-LGR groundwater there was free of contamination. The transducer recorded pumping levels and water level recovery. It was removed about 6 days after the end of pumping. A permanent, new 5 hp Goulds pump was installed at 325 feet bgs on June 27, 2003. Power is supplied through an overhead City Public Service (CPS) line that terminates on a pole adjacent to the old CS-H location.
Agricultural well CS-I is located in the remote northeast portion of the North Pasture. Its purpose is to maintain water troughs and a small pond for livestock and wildlife. The well is included in the CSSA Quarterly Groundwater Monitoring network. The windmill and sucker rod apparatus had not been functioning properly. After troubleshooting the system and attempting unsuccessful minor repairs, GPI received the approval from CSSA to remove the sucker rod system and install a solar-powered pumping system. The upgrade was preceded by a geophysical survey to determine the depth and formational penetration of the well. The improvements were completed in September 2003. At that time the well was maintaining a discharge rate of 4 gpm. The well has been redesignated CS-I-LGR.
Installation of the new TO42 MWs followed the same basic procedures as previous RL83 work. Seventeen new deep MWs were installed during TO42 field operations to facilitate monitoring portions of the Middle Trinity Aquifer beneath CSSA. Wells CS‑MW11B-LGR and CS-MWH-LGR were constructed after special circumstances developed during work at CS-MW11A-LGR and CS-H. Several of the new wells were clusters of two or three wells each; these include clusters CS-MW1 (three wells), CS‑MW2 (two wells), CS‑MW11 (two wells - LGR only), CS-MW12 (three wells), and CS‑MW16 (two wells). Non-clustered wells CS-MW17-LGR, CS-MW18-LGR, and CS‑MW19‑LGR were exclusively constructed to monitor the LGR portion of the Aquifer. All the new MWs were completed either in the LGR, BS, or CC members of the Middle Trinity Aquifer.
Four WB wells were installed to monitor selected zones within the subsurface around the southwest portion of CSSA. The wells at CS-WB01, CS-WB02 and CS-WB03 were completed in the LGR. Construction there also allowed monitoring of the basal section of the UGR. The WB construction at CS-WB04 allows monitoring of all three formations plus the bottom of the UGR through a single borehole.
CS-MW18-LGR was constructed within the Inner Cantonment, on the south side of the former firehouse (Figure 2.1) beginning on July 18, 2002. Total depth cored was 422 feet bgs. The LGR/BS contact was encountered at 413 feet bgs. Large voids or washouts were encountered in the top 100 feet of coring. Drilling fluids and fine suspended cuttings were contained in adjacent rolloff containers. Drilling returns were frequently lost during coring, presumably to voids and fractures within the borehole.
Geophysical logging of CS-MW18-LGR occurred on July 23, 2002, and DIGW sampling on the following day. Based on analysis of the gamma, SP, resistivity, and video logs, the intervals for three DIGW samples and three alternates were selected. Three samples were successfully collected. One zone (239-251 feet bgs) yielded insufficient flow for sampling.
Using the Gardner-Denver 1500 drilling rig, the borehole was reamed to 8 inches diameter. The TOTCO surveys, collected every 50 feet, were within the specifications required by the Work Plan. The screened interval selected was from 385 to 410 feet bgs. The well was completed as described in Section 2.4 on July 29, 2002. Chemical analysis indicated that drilling fluids were not contaminated. Contained water from the rolloffs was discharged to ground surface and drilling mud was deposited in the cuttings pit adjacent to the CS-MW19-LGR location.
Elevated pH was detected at MW18-LGR during September 2003 on-post groundwater monitoring. In response, a camera survey was taken of the borehole to confirm the well casing was intact. After the casing was determined to be competent, Parsons directed GPI to perform additional development. Previous quarterly monitoring showed no contaminant concentrations above the maximum contaminant level (MCL). The water was discharged to ground surface. Redevelopment continued until pH values returned to the normal range. Approximately 12,800 gallons were pumped from MW18-LGR in October 2003.
This new well is located on a small rise in the middle of the Inner Cantonment. GPI mobilized to CS-MW19-LGR and started coring on July 30, 2002. Coring continued to a final depth of 382 feet bgs, achieved on August 2, 2002. After geophysical logging (no video) three DIGW samples were collected. The well was reamed to 8 inches after backplugging the corehole to 365 feet bgs. A 4-inch diameter stainless steel screen set between 340 and 365 feet bgs (bottom of LGR), sand pack, and seal were installed on August 9, 2002.
After bailing, 2,200 gallons were developed from CS-MW19-LGR on September 5, 2002. The development discharge was treated at the GAC. Because chemical analysis indicated that contained drilling fluids were not contaminated, the rolloffs were discharged to ground surface and drilling mud was deposited in the cuttings pit adjacent to the CS-MW19-LGR location. During subsequent quarterly monitoring, the pH of CS-MW19-LGR purge water was initially above normal. The pH decreased to acceptable values after purging several additional gallons and samples were collected.
Coring of CS-MW17-LGR began on August 12, 2002 on a hilltop about 1,800 feet northeast of Gate 7, in the East Pasture. Coring continued to 401 feet bgs. The LGR/BS contact was determined to be at 391 feet bgs after examination of the logs and core samples. The contact in CS-MW17-LGR exhibits highly pyritized fossil molds. Geophysical logging of CS-MW17-LGR occurred on August 15, 2002, the same day coring was completed to the BS. No DIGW sampling was conducted at CS-MW17-LGR. Reaming to 8 inches diameter began on August 16, 2002, and the well was screened and sealed on August 20, 2002. CS‑MW17-LGR is screened 367 to 392 feet bgs, at the bottom of the LGR.
A volume of 1,388 gallons was developed from MW17 during September 3 to 4, 2002. The development discharge was contained until chemical analysis verified no contaminant concentrations above the MCL, then was released to the ground.
Chemical analysis indicated that used drilling fluids were not contaminated. Contained water from the rolloffs was discharged to ground surface and drilling mud was deposited in the cuttings pit located near CS-MW19-LGR.
3.2.4 CS-MW12 Cluster Wells
The site for the CS-MW12 cluster wells is in the northwest quadrant of the Inner Cantonment, approximately 200 feet west of areas H and I, between Road D-24 and a westerly gravel extension of Tenberg Drive. The purpose of work at this site was to install an LGR, BS, and CC well cluster. The LGR well was constructed first, followed by the CC, and then BS wells. Drilling fluids and ejected cuttings were contained in the rig containment and five rolloff boxes staged on site until laboratory analysis showed the material to be uncontaminated.
GPI mobilized to the site on September 9, 2002 and coring began the following day at CS‑MW12-LGR. The well was cored to 382 feet bgs. After geophysical logging, four DIGW samples were successfully collected after attempts were made at seven intervals. Low yield prevented sample collection from three zones. CS-MW12-LGR was then partially backplugged and reamed to 8 inches to a depth of 358.5 feet bgs.
The drill rig moved off the LGR hole after reaming to undergo decontamination and then parked over the CS-MW12-CC point on September 18, 2002. The screened interval was emplaced in CS‑MW12‑LGR at 333 to 358 feet bgs using the GPI winch truck.
Drilling commenced at CS-MW12-CC on September 19, 2002. As the LGR was already logged on this site, core sampling through the LGR was not necessary at CS-MW12-CC. Therefore, CS-MW12-CC was drilled directly at 8 inches diameter from ground level into the BS, to 372 feet bgs. Drilling was paused every 50 feet and TOTCO shots were taken as required. Analysis of fluids from CS‑MW12‑LGR drilling indicated no contamination, so water produced during drilling was released to ground surface from containment once solids had settled out. Coring resumed at 372 feet in CS-MW12‑CC continuing to 502 feet. Geo Cam conducted logging of the BS and CC in CS‑MW12‑CC corehole and two DIGW samples were collected on September 26, 2002. Discrete interval sampling was completed the next day, and the corehole was backplugged into the BS to prevent possible downward spreading of contamination into the water-bearing zones of the CC during well construction. Laboratory results of ejected drilling fluids and DIGW samples indicated no contamination. Since no contamination was detected in the LGR and BS at this locale, a single-cased CC well was adequate. The hole was reamed from 372 to 465.5 feet bgs to 8 inches on September 30, 2002. The CS-MW12-CC screen was set at 440 to 465 feet on October 1, 2002. Drilling fluids generated by CC coring and reaming also proved to contain no contaminants. The water was released to ground surface after solids had settled out. In October the well was developed until stabilization criteria were attained.
Subsequent monitoring revealed pH of groundwater at CS-MW12-CC had become elevated. During January and February 2003 Parsons conducted additional development at the well. Water quality field parameters were monitored periodically. Stabilization of pH to normal values was obtained after pumping approximately 31,800 gallons.
The same day CS-MW12-CC was set, the rig moved over to the CS-MW12-BS location, between the LGR and CC wells, and started drilling. Since the geology was logged during the LGR and CC wells installation, the BS well was drilled directly to its final depth of 408 feet to 8 inches diameter. No logging and no discrete sampling were conducted. The screen at CS‑MW12-BS was set at 382 to 407 feet bgs.
The LGR/BS contact was determined to be 358 feet bgs, the BS/CC at 413 feet bgs, and the CC/Hammett Shale (HS) at 488 feet bgs in this location. Characterization of drilling fluids from construction at this cluster showed no contamination. Water and cuttings were eventually released to ground surface. The CS-MW12 wells had lifts of grout periodically added over the next few weeks until ground surface minus 1 foot was attained.
Occasionally, during subsequent quarterly monitoring, the pH of CS-MW12-BS purge water was initially above normal. The pH lowered to acceptable values after purging several additional gallons.
This site lies outside the north edge of CSSA�s H and I sections, between Central Road and Moyer Road, in the northeast quadrant of the Inner Cantonment. Drilling at the CS‑MW1 cluster added BS and CC MWs adjacent to the recently upgraded CS‑MW1-LGR well, completing a cluster of three wells. Contaminants historically have been detected in CS‑MW1-LGR groundwater, so monitoring of the BS and CC in this area was considered to be warranted. The two new well locations align with existing CS‑MW1-LGR in an east-west direction. CS‑MW1‑LGR was upgraded at the beginning of the TO42 field effort with new 3‑inch diameter casing and screen. Due to subsurface conditions encountered while drilling, the original CC borehole was redesignated and constructed as the CS‑MW1-BS well. The CC well was installed last in the center position of the cluster. Major work on the two new wells at this site proceeded from October 15 to December 20, 2002.
During well construction drilling fluids and ejected cuttings were contained in the rig containment and rolloff boxes staged on site. The significant volume of very fine solids in the ejected fluids necessitated long settling times. Buildup of fluids soon outpaced the rate at which water could be treated at the GAC. In response, a bag filtration unit (BFU) was acquired by Parsons to filter the water on site during transfer from containment to the GPI vacuum truck, thus reducing time between fluid generation and treatment and freeing up containment space more quickly. According to Parsons records, 83,299 gallons of drilling fluids and groundwater produced at the CS‑MW1 site were treated at the GAC from October to December 2002.
Coring at this well site began on October 15, 2002 with the intention of constructing a CC well. The LGR was cored through to the top of the BS. Geophysical logging was conducted on October 18, 2002. Reaming the LGR to 12 inches diameter commenced the next day. The LGR was cased off here before advancing the hole deeper into the underlying formations due to the presence of contaminants. A double-cased well was planned using 8-inch steel casing in the LGR portion and 4-inch PVC from surface stickup to the screen in the CC. After review of logs, casing was set at 328 feet, 8 feet below the LGR/BS contact. More than 2 days of reaming time were lost during the week of October 21-25, 2002 due to inclement weather. Reaming resumed the following week. After reaching a depth of 200 feet bgs, the borehole began producing much more water than expected. On November 1, 2002 the rolloff containment reached maximum capacity as the final drilling depth drew near. Parsons had been operating the GAC full-time, but water production easily outpaced the capacity of the GAC unit. Drilling was temporarily halted while treatment caught up. Two additional rolloff boxes were delivered to expand containment capacity. GPI personnel concentrated on surface completions at the CS‑MW12 cluster during this time. Reaming the LGR portion of the well was completed on November 5, 2002, and 8-inch steel casing was installed the next day. The required 24-hour setting period for new grout passed before work on the well proceeded.
As a result of the excessive quantities of groundwater to be treated, a BFU was brought on-site to facilitate the treatment process. The portable unit was used to filter sediments from the waste stream prior to GAC treatment. The end result was that more groundwater could be managed and treated in a more efficient and effective manner.
The next step consisted of drilling an 8-inch diameter hole through the shoe at the bottom of the casing to the depth where coring had stopped. On November 8, 2002, the BS was cored from 352 to 382 feet bgs. The BS/CC contact was encountered at 379.5 feet. The open BS section of the corehole was washed and blown out. Knowing the overlying LGR at CS‑MW1‑LGR was contaminated, the BS was sampled as well. A submersible pump was set 6.5 feet above the bottom of the hole. The open interval was pumped out twice to the extent allowed by the intake setting. The well was allowed to recover overnight. The next day Parsons collected a groundwater sample from the open section of the corehole via submersible pump after purging 430 gallons over two days. Geo Cam then performed geophysical logging of the BS section.
Results of the BS sampling showed low concentrations of TCE, PCE, and DCE in the BS water. To prevent possible downward migration of contamination from the BS to CC, Parsons and CSSA decided at this time to construct the well as a BS well. Drilling water was transported to the GAC via GPI vacuum truck for treatment. Occasionally, during subsequent quarterly monitoring, the pH of CS-MW1-BS purge water was above the normal 6.5 � 8 of other on-post wells, but remained within acceptable ranges for sampling and analysis purposes.
3.2.5.2 CS-MW1-CC
Drilling the LGR section of CS-MW1-CC commenced on November 14, 2002 immediately following setting of the BS well screen. The hole was advanced to 330 feet with a 12‑inch tri-cone roller bit followed by reaming to a 16 inch diameter to a depth of 328 feet. Casing with 12‑inch diameter and a drillable cement shoe was installed to 328.4 feet bgs on December 6, 2002. The annular space was plugged with grout in batches, allowing time for the grout to set before drilling resumed. The shoe was drilled out and a 12‑inch diameter hole was drilled through the BS to 380 feet bgs. On December 13, 2002, 8-inch casing was seated in a very hard layer half a foot into the top of the CC to close off the BS.
While drilling through the shoe at the bottom of the 8‑inch casing, a large steel pin broke free of the drill rig table and fell into the hole. The item was fished out by using a core-catching bit that GPI manufactured. Coring the 91 feet of the CC segment to 472 feet bgs began and finished on December 18, 2002. The next day the corehole was geophysically logged, three DIGW samples were taken, the corehole was plugged back with bentonite to 425 feet bgs, and then reamed to an 8‑inch diameter to a depth of 420 feet bgs. Examination of the logs showed that the CC/HS contact was encountered at 454 feet bgs. The screen was set and sealed from 394.7 to 419.7 feet bgs on December 20, 2002. Drilling fluids were processed through the GAC almost every day during MW1-CC construction.
Grouting to ground surface and well pad construction at the CS‑MW1 well cluster was completed in January 2003.
Coring of the LGR at CS‑MW2-CC began 30 feet upslope from the existing CS‑MW2‑LGR on January 8, 2003, and was completed January 10th. A detailed log for the LGR at this location did not exist. Reaming started after geophysical logging of the LGR on January 13th. The LGR was first reamed to 12 inches, and then 16 inches to provide for triple casing as CS‑MW2‑LGR sampling results exhibited contamination at this location. Previous experience at CS‑MW1‑BS and CC showed that the BS would not be contaminant-free and, therefore, sufficient-sized hole was installed in the event a triple-cased well might be required. Since the LGR was already monitored by CS‑MW2-LGR, no LGR DIGW samples were collected from the CS‑MW2‑CC corehole. During reaming TOTCO shots showed the hole was approaching the maximum allowable drift of 2 degrees off vertical. Two days were spent re-reaming with a 12-�-inch stabilizer bit added to the drill string to correct the plumbness of the hole. The 12‑inch diameter drilling finished on February 6, 2003 and 16‑inch reaming began immediately afterward, being completed to 357 feet bgs on February 19, 2003. Casing installation was delayed due to severe weather, eventually being installed on February 25, 2003.
Bexar Shale coring and geophysical logging were accomplished on February 27, 2003. No DIGW samples were attempted in the BS at this site. The BS corehole was, however, bailed dry twice over the next 2 days, and then sampled by bailer on the third day. Results of the bailer sample analysis indicated no TCE or PCE, but did show low concentrations (below MCLs) of acetone and toluene. These constituents have a high probability of being artifacts of the drilling process and are not considered part of the contamination plume. These results did not justify extra work to ream and case off the BS. Coring in CS‑MW1-CC resumed and finished at 492 feet bgs, 14 feet into the HS, on March 5, 2003. Geo Cam arrived that same day and logged the CC/HS. The final TOTCO surveys, collected every 50 feet, were within the specifications required by the Work Plan. Three DIGW samples were collected from the corehole. The remaining corehole was backplugged with bentonite to 450 feet bgs and then reamed to 8 inches diameter. The screened interval was set from 425.7 to 450.7 feet bgs on March 8, 2003.
Contained drilling fluids remaining on site were released to ground surface after chemical analysis showed no contamination. Cuttings were transported and deposited at the cuttings pit near CS‑MW19‑LGR.
3.3 - CS-MW11 Well Pair
Original plans called for one LGR MW in this area. The CS‑MW11 well pair is located just east of the old borrow pit/disposal pit now designated as SWMU B-29, south of Butler Road. The subsurface in the area is believed to be faulted. Atypical geologic structure and hydrologic conditions were encountered during drilling of the first MW11A. Subsequently, a second well MW11B was constructed to monitor an additional zone in an extended LGR hydrogeologic unit. Work at the MW11 site began on March 10, 2003 and continued through April 2003.
Coring started on March 11, 2003. Several very hard layers were encountered between 250 and 262 feet bgs. These hard zones slowed the coring rate considerably. Core runs were shortened but sample recovery from the runs continued to be very poor. Softer material between the hard zones was often apparently ground up and washed away during slow coring of the very hard material. Caliper logs later showed voids and/or washouts throughout the interval from 240 to 260 feet.
By March 19, 2003 the estimated depth to the LGR/BS contact had been passed by over 50 feet. The contact had not yet been encountered and the geology was found to be atypical; therefore, the corehole was geophysically logged. At this point the corehole depth was 414 feet bgs, a depth where the CC is usually found. Geophysical logging confirmed that the hole was still completely within the LGR. Several DIGW samples were collected while the coring string was out of the hole. It was decided to ream the hole to 8 inches to facilitate deeper coring. Reaming was temporarily halted as an estimated 200 gpm production of groundwater outpaced the ability to contain and treat it. The depth of the reamed hole at this point was about 240 feet bgs. The earlier drilling fluid and DIGW sample analysis was rushed and results showed no contamination. To alleviate the containment problem, the noncontaminated unsettled water was pumped through a dual BFU to reduce turbidity, and discharged to ground surface.
Coring was continued to 494 feet bgs after the well was reamed to 414 feet bgs. A second complete geophysical log and a video survey were run in the well. Two additional DIGW samples were collected from the newly cored section. The corehole was backplugged to 445 feet bgs and reamed from 414 to 445.5 feet. Drilling fluids from the second coring and reaming phase were contained until sampling indicated the absence of contamination. On April 1, 2003 the screen was set in CS‑MW11 from 420.3 to 445.3 feet bgs. Due to the unusually deep depth of the LGR found at the CS‑MW11 site, a second LGR well was decided upon for additional monitoring of significant water-bearing zones. The first CS‑MW11 well was designated as CS-MW11A-LGR. All remaining water generated by CS‑MW11A‑LGR construction was released to ground surface, while the cuttings stayed in the rolloff. The TOTCO surveys, conducted every 50 feet, were within the specifications required by the Work Plan.
To avoid grout fluids being intercepted by the screened zone of the adjacent MW11B‑LGR, grouting at CS‑MW11A was suspended at 246.8 feet bgs until the �B� well was completed. Then the corresponding annular space in the �A� well overlapping the screened zone of the �B� well was filled with bentonite chips, and with sand where voids were identified, from 171.5 to 246.8 feet. The annulus above 171.5 feet was grouted in the usual manner.
3.3.2 CS-MW11B-LGR
Since an adequate core sample record of the LGR was obtained during CS‑MW11A‑LGR activities, there was no coring of CS‑MW11B‑LGR. CS‑MW11B‑LGR drilling began with an 8‑inch bit at a location 25 feet west of CS‑MW11A‑LGR on April 2, 2003. Groundwater from CS‑MW11B‑LGR was periodically sampled, however. As the borehole advanced, drilling was temporarily halted at selected low permeable zones, and a single packer sampling apparatus was used to extract a groundwater sample. The apparatus operated in the same manner as the standard double packer system used in other wells, except the borehole bottom substituted for the lower packer below the pump. Zones sampled in CS‑MW11B included 0‑140, 145‑176, 179‑213, and 217‑260 feet bgs. Drilling to 260 feet bgs and geophysical logging were completed on April 8, 2003.
Installation of CS‑MW11B‑LGR screen and riser was withheld until results of groundwater sample analyses were received and reviewed. The hole was backplugged to 207.5 feet bgs and the screen set at 182 to 207 feet on April 16, 2003. Well construction proceeded in the normal manner. Final work on CS‑MW11A-LGR and CS‑MW11B-LGR overlapped with initial operations at CS‑MW16‑CC.
3.3.3 CS-MW16-CC
Well CS-MW16-CC was installed 29 feet west-northwest of upgraded CS‑MW16‑LGR. Existing utilities, streambeds, and future infrastructure work limited the specific locations available for another MW in the MW16‑LGR vicinity. Since groundwater contamination is well documented in the MW16 area, CS‑MW16‑CC was designed as a triple-cased MW. All ejected drilling fluids were contained and filtered at the CS‑MW16-CC site and treated at the adjacent GAC system.
The drill rig mobilized to CS‑MW16-CC on April 10, 2003. Coring of the LGR at MW16 began the next day. Geo Cam performed gamma, resistivity, and caliper logging and COLOG initiated HpL of the 343‑foot deep LGR corehole on April 16, 2003. As a demonstration of capabilities, COLOG conducted ambient logging on the first day, and logged under pumping conditions the second day. COLOG would be logging and analyzing data at the four WB wells scheduled for later construction. Based on COLOG data two DIGW sampling zones were selected. Samples were collected from intervals 190�202 feet and 315�327 feet bgs on April 21, 2003. These zones were identified by COLOG as contributing zones during their 6 gpm pumping log in open corehole.
Reaming of the 4.25‑inch corehole to 16 inches started on April 22, 2003. A final 16‑inch reamed depth of 336 feet bgs was achieved on May 20, 2003. To carefully monitor vertical drift while drilling from 4 to 16 inches diameter, TOTCO shots were taken every 20 feet to 260 feet bgs.
Unusual algal growth and odor were observed in the contained drilling fluids at this time. A groundwater sample was collected by bailer from the CS‑MW16-CC borehole to analyze for evidence of aerobic and anaerobic bacteria. Laboratory results showed no excessive amounts of either.
The 12-inch casing through the LGR portion of CS‑MW16-CC was set at 335.5 feet bgs and grouted in place on May 22, 2003. Grout was pumped via tremie pipe down the inside of the casing to the hole in the shoe. Grout filled both the casing and outside annular space from the bottom up, to 320 feet bgs.
Before coring could resume the 15.5‑foot grout filling inside the casing was drilled out. Drilling out the grout plug down to where coring stopped at 343 feet bgs was completed on May 27, 2003. The BS was cored to 393 feet bgs, about 9 feet into the CC that same day. The large amount of cement grout cuttings appeared to raise the pH of the used drilling fluids considerably. To meet GAC treatment compliance limits, muriatic acid was added to the filtered water in proportion to reduce the pH to a 6�9 range.
The BS at CS‑MW16-CC was geophysically logged, reamed to 12 inches diameter, and had 8‑inch casing set at 393 feet bgs. Coring of the CC to 473 feet bgs and geophysical logging was completed on June 3, 2003. The following day two DIGW samples were collected and the corehole was backplugged to 425 feet bgs with bentonite chips. The CC at CS‑MW16-CC was reamed at 8 inches to 431 feet bgs. The stainless steel screen and Certa‑Lok� PVC riser installation was finished on June 16, 2003. At CS‑MW16-CC a 4‑inch ID screen and casing were needed to accommodate a standard 4‑inch well pump. The well was designed for the purpose of possibly conducting a future short-term pump and treat pilot study. The usual schedule 80 PVC casing used in CSSA MWs did not meet the necessary requirements to accommodate anything larger than a 3‑inch pump.
Surface completion work and grouting of the annuli in the triple-cased CS-MW16-CC occurred periodically through mid-October. An interim 1.5 hp submersible pump was emplaced and plumbed in July 2003, to function on an interim basis for possible pumping to the GAC system.
3.4 - Multi-Port Well Installation
There were four WB multi-port wells constructed for CSSA as part of the TO42 Well Installation fieldwork. The three on-post WB wells, CS‑WB01 through CS‑WB03, were completed in the LGR portion of the Aquifer. The fourth WB well, CS‑WB04, was completed with sampling ports in all three members of the Aquifer. Installation was carried out in a phased approach to minimize subcontractor mobilization and standby costs. The wells were first cored and developed by GPI and Parsons geologists in the standard manner. Coring at the on-post holes was terminated in an impermeable layer, at a depth several feet above the first major water-bearing zone near the bottom of the LGR. Off‑post CS-WB04 was cored through the three Middle Trinity Aquifer members.
Each hole was geophysically logged by Geo Cam. Flexible FLUTe liners were emplaced in the coreholes to seal them and prevent any potential vertical migration of groundwater contaminants. Work on the first liner used was performed by a trained FLUTe technician. Parsons, GPI, and CSSA (Portage) personnel assisted under direction of FLUTe. Thereafter, Parsons and CSSA worked the liner insertions and extractions.
Emplacement of the liners immediately followed DIGW sampling operations and development at each corehole. The liners were later removed to allow COLOG to proceeded from well to well with HpL. The FLUTe liners were reinstalled after COLOG finished logging at each well. The four coreholes remained sealed until Westbay personnel arrived in mid-August to complete the final phase of WB well construction.
Each WB system installation consisted of several steps. First, the various geologic logs were reviewed with the Westbay crew chief and some of the sampling zone intervals were refined. The sampling and pumping ports string assembly was done in sections according to the intervals selected. Westbay assembled the sections into transportable lengths in the CSSA firehouse (since demolished). The sections were wrapped in clean plastic then transported to the well site for emplacement. Each coupling with a sampling port was vacuum tested during installation. Work proceeded through the weekend to limit standby time. On August 28 and 29, 2003, Westbay conducted system operations training for CSSA and Parsons personnel. WB well sampling was first conducted in mid-September 2003. Surface completions at the four WB wells were built by GPI in October 2003.
The site for this well was selected for its apparent location on the south side of a local fault block in the AOC‑65 area. The well is 58 feet east of CS-MW8-CC on level ground, south of AOC‑65. Coring to 314 feet bgs was accomplished June 9-11, 2003. Elevated PID readings from the core sample were recorded from approximately 10 to 25 feet bgs. A rock sample from the 14�14.5-foot depth interval was collected and sent to Severn-Trent Laboratories, Arvada, Colorado for VOC analysis. Excess drilling fluids were contained in a rolloff box stationed adjacent to the coring site. Immediately after coring the drill rig was decontaminated and mobilized to WB02.
Geophysical logging and DIGW sample collection took place the day after coring was completed. On June 12, 2003 one DIGW sample was successfully collected out of four attempts. Intervals above 237 feet bgs turned out to be either dry or too low-yielding to obtain a water sample. The next day three more discrete interval sample collections were attempted with one success. This sampled zone was at the bottom of the hole, 297 to 309 feet bgs. After interval sampling, the WB01 corehole was developed. A video log of CS‑WB01 was made on June 16 after the corehole water had cleared over the weekend.
Hydrophysical logging was not scheduled until mid-July. To prevent downward migration of contaminants in the meantime, a FLUTe flexible nylon liner was installed into CS‑WB01 on June 17, 2003. As this was the first in a series of FLUTe liner installations, FLUTe personnel assisted Parsons field team members and CSSA personnel with the emplacement.
Hydrophysical logging by COLOG was conducted at CS‑WB01 from July 16 - 18, 2003. Parsons and CSSA had removed the nylon liner the previous day and returned it to FLUTe for repair of a tear. After COLOG was finished, the liner removed from CS‑WB02 was washed and inserted into CS‑WB01. Installation of the WB system was scheduled for late August. The flexible liner was reinstalled during the interim.
The CS‑WB01 FLUTe liner was again extracted on August 19, 2003. The corehole was further developed after GPI tagged bottom at 314 feet bgs to insure that no infilling had occurred. A possible collapse of some portion of the cored hole was considered possible, as liner removal had been slow and difficult. Westbay and GPI personnel installed the multi-port system on August 22, 2003. The system comprises 10 isolated monitoring intervals. Integrity of the system was tested the following day by profiling each interval with a MOSDAX pressure probe. The test indicated all zones were properly sealed and the ports functioned properly.
The CS‑WB02 location sits atop a backfilled area where a former underground storage tank (UST) was located, 73 feet southwest of Building 89. An 8‑inch hole was first drilled through asphalt and backfilled to hard bedrock at 27 feet bgs. Surface casing consisting of 4‑inch diameter PVC was grouted in place to close off the former UST backfill from the WB hole. Coring of WB02 began on June 17, 2003 starting at 27 feet bgs, and was completed to 313 feet bgs on June 19, 2003.
While tripping in pump and pipe for development, the drillers found the corehole blocked at about 30 feet bgs. A 4‑inch bit drill string was run up and down the hole several times because some zones continued to collapse slightly, causing bridging and infilling. The drillers eventually cleaned out the hole. The next day, June 20, CS‑WB02 was geophysically logged and three DIGW samples were attempted resulting in one sample obtained. Logging indicated that approximately 4 feet of infilling had accumulated at the bottom of the hole. Finally, a fourth DIGW sample was acquired by single packer and pump from the bottom 12 feet of the corehole, 297-309 feet bgs. Development of the corehole proceeded after that. Video logging was conducted the next day on June 24, 2003.
First attempts to emplace a FLUTe liner into CS‑WB02 failed. The leading edge of the everting liner caught on void space ledges preventing it from deploying into the well. Finally a Grundfos pump on a flexible hose line was lowered into the liner and used as a guide to help the leading edge of the liner push by the ledges in the well wall. The FLUTe liner was fully set in CS‑WB02 on June 25, 2003.
Several weeks later the CS‑WB02 liner was pulled to make the corehole accessible to COLOG for HpL, which took place between July 20 and 22, 2003. COLOG experienced the same difficulty inserting its equipment into the hole as Parsons did inserting the FLUTe liner. Despite the accessibility difficulties, COLOG successfully completed logging on schedule. The FLUTe liner previously sent for repair (originally used at CS‑WB01) returned and was inserted into CS‑WB02.
In mid-August the liner was pulled out again after a 2‑day effort. The liner was torn in the process. Following additional development, Westbay and GPI personnel installed the CS‑WB02 multi-port system on August 25, 2003. There are 10 isolated monitoring intervals contained in the CS‑WB02 system. Integrity of the system was tested 2 days later by profiling each interval with a MOSDAX pressure probe. The test indicated all zones were properly sealed and the ports functioned properly.
The well is situated 64 feet west of Building 90 amidst several AOC‑65 vapor extraction and vapor MWs. This location is in a fault block situated slightly above the blocks to the south. Coring of CS‑WB03 occurred June 24-26, 2003 to a depth of 312 feet. Geo Cam logged the hole the next day. Discrete interval sampling followed with four successful sample collections out of five attempts. The well was then developed. Parsons installed the FLUTe liner for CS‑WB03 on July 2, 2003.
Parsons took 2 days, July 21 and 22, to completely extract the flexible liner from CS‑WB03. COLOG performed HpL on July 23 and 24, 2003, and the liner was reinserted on the 25th.
On August 25, 2003 the FLUTe liner was pulled from CS‑WB03. An additional 2,250 gallons of groundwater was extracted during supplementary borehole development on the following day. The Westbay personnel installed the multi-port sampling system the same day (August 26, 2003). The system comprises 10 isolated monitoring intervals. Profiling of the CS‑WB03 intervals on August 27 showed the system to be operating properly.
The CS‑WB04 well is located off-post, approximately 1,200 feet southwest of Building 90 and 160 feet east of private water well RFR-10. It is aligned with the strike of the faults that pass through AOC‑65 and in line with VOC Plume 2 advancement. Prior to drilling, RFR-10 was taken off-line to avoid potential water quality problems, and an alternative water source for the RFR-10 residence was established.
Mobilization to CS-WB04 and overdrilling to 8 feet took place on July 2, 2003. The hole was reamed to 21 feet at a 6‑inch diameter and surface casing consisting of 4.5‑inch ID PVC was inserted. The hole was cored at 4.5-inch diameter with GPI�s Gardner-Denver 1,500 drilling rig to 442 feet bgs from July 7-9, 2003.
A very hard layer was encountered at a depth of 442 feet. Attempts at coring through this layer rendered GPI�s coring bit useless. At one point the drilling rig was operating at 14,000 psi while taking over an hour to advance just 2 feet. Later analysis showed the zone, which is immediately below the BS-CC contact, to be highly quartzose. Coring operations paused while a new bit was ordered. The new, second bit was also worn down while advancing only 0.5 foot. Coring operations were again temporarily halted. On July 14 GPI drilled 2 feet through the quartzose zone, from 442 to 444 feet bgs with a modified 4‑inch diameter diamond drill bit. Coring then proceeded at a 4‑inch diameter. The well was cored 0.5‑feet into the HS, for a total depth of 513 feet bgs. Coring ended on July 16, 2003.
Geo Cam performed geophysical and video logging at CS‑WB04 on July 17, 2003. It was not necessary to insert a FLUTe liner into the corehole, since COLOG immediately mobilized to CS‑WB04. HpL by COLOG was accomplished July 18 and 19, 2003. Collection of DIGW samples took place July 21-24, 2003. Six DIGW samples were obtained after seven attempts. Of the zones tested, the interval 242�254 feet bgs did not yield sufficient groundwater for sampling. The corehole was developed on July 25, 2003. The FLUTe liner was installed August 1, 2003. The leading front of the liner could not be advanced past about 441 feet bgs, where the caliper log showed minor washout and ledges at the BS/CC contact. The hole was effectively sealed above 441 feet.
Liner removal at CS‑WB04 occurred August 18, 2003. GPI conducted some additional development while the hole was open. The WB system was installed August 19-20, 2003 by WB and GPI personnel, and supervised by Parsons. The system at CS‑WB04 comprises 16 isolated zones with sampling and pumping ports. Each interval was examined for integrity after packers were inflated. A string of demonstration pressure probes was then inserted and set into the CS‑WB04 system. The probes monitored 11 of the deeper intervals recording hydrostatic pressure fluctuations caused by natural conditions and pumping in nearby well RFR‑10. Parsons removed the MOSDAX string from CS‑WB04 on September 17, 2003 and shipped the equipment back to Westbay Instruments.