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Section 15 - TO42 Work Plan Addendum for Installation of Monitoring Wells, Upgrades, and Groundwater Sampling

15.1 - Statement of Objective

This addendum to the work plan describes activities in support of the installation of 17 monitoring wells to be installed in three units of the Middle Trinity aquifer underlying CSSA. Ancillary tasks also addressed with this addendum are the upgrade of five existing wells, waste management, and installation of sampling pumps and pressure transducers. The field investigation will be documented in a field report, and data obtained from the investigation will be incorporated into the CSSA Conceptual Site Model (CSM). Quarterly groundwater monitoring will also be performed under this delivery order starting March 2002. A total of seven rounds of groundwater will be collected in conjunction with other existing delivery orders. This delivery order will eventually handle the sampling and analysis of all on-post and off-post wells through September 2003.

15.2 - General Well Installation/Upgrade Requirements

The following paragraphs describe the planned field activities and procedures. More detailed discussions on the procedures are in the Scoping Documents of this Encyclopedia, Volume 1-4, "Sampling and Analysis Plan" (SAP), behind tab "TO42 Addendum."

The current drilling program includes four wells to complement three existing well locations. Five other wells will be arranged in clusters of two or three each at two locations. Four non-clustered wells to monitor the Lower Glen Rose portion of the aquifer exclusively, and four Westbay multi-port monitoring devices within the upper 300 feet of the Glen Rose member at Plume 2. Figure 15.1 illustrates the proposed drilling locations within CSSA.

Upon completion of the task order, CSSA will have the following monitoring network of 40 wells that include well casing and screen and nine open borehole completions (51 total):

Actual drilling depth will be a function of each well’s location and land surface elevation and/or proximity to structural features (e.g., faults). Depending on the drilling location at CSSA, up to 100 feet of Upper Glen Rose (UGR) limestone may also be penetrated. During the actual fieldwork, drilling depths will extend to the appropriate formational contacts. If necessary, total drilling footage greater than that in the statement of work (SOW) will be addressed with a scope modification as field conditions warrant. The estimated drilling depths are as follows:

As specified in Table 15.1, selected well locations will be cored and sampled continuously from ground surface to the total depth, unless that location has been previously cored. In those cases, coring will resume at the approximate depth attained during prior investigations. Within clusters, different hydrologic zones may be cored between wells to avoid significant velocity losses between large surface casings and the small diameter coring string (e.g., cutting removal from a 4.5-inch coring bit within a 12-inch ID surface casing).

When necessary, the corehole will be cased with temporary or permanent surface casing to minimize the downward migration of contaminants. Each corehole will be geophysically logged. Video surveys will be conducted at select locations. Discrete groundwater samples will be collected from each boring using an inflatable isolation packer system. As many as five discrete samples will be collected from each hydrogeologic zone at select monitoring well locations.

Table 15.1 - Estimated Quantities of Drilling Requirements

Depending on the risk of cross-contamination, the drilling subcontractor shall install protective surface casing in each borehole before proceeding to the next hydrologic unit as directed. All surface casing will be composed of welded steel pipe. The annular seals (grout) will be placed via tremie pipe.

The interior 4-inch ID PVC casing and 304 stainless steel casing and screen will be installed in each well (13 wells plus two upgrades) to limit the amount of open borehole to less than 25 feet. The well riser will consist of Schedule 80 PVC with a nominal 4-inch ID with flush-threaded joints. The well screen will be constructed of 304 stainless steel wire-wrapped screen with a slot size of 0.050-inches (50-slot), with no more than a 25-foot intake. Two other well upgrades will follow a similar design, but will utilize nominal 3-inch ID casing and screen.

The annular space will be filled with an 8/16-mesh filter pack from the base of the borehole to height of 2 feet above the top of the screened interval. A 100 percent sodium bentonite seal with a maximum thickness of 5 feet will be emplaced within the borehole above the filter pack. The bentonite seal will be allowed to fully hydrate per the manufacturer’s specifications before grouting activities commence. Beginning with small lifts, a Portland/bentonite grout mixture will be slowly pumped into the annular space using a side-discharge tremie pipe. The grout will be allowed to cure for at least 48 hours prior to well development.

Wells will be completed with 4-foot square concrete pads with a locking well protector and protector posts in accordance with state regulations. A rounded brass monument will be placed on each monitoring well concrete pad to serve as a permanent benchmark. Each well will be surveyed by a registered land surveyor. All wells will be secured as soon as possible after drilling with corrosion-resistant locks.

Decontamination will take place between drilling of hydrologic zones and relocating to different well clusters. A minimum of 24 hours will pass after the emplacement of casing grout before proceeding to the next hydrologic unit.

Depending on location, various hydrostratigraphic units will be cored as shown in Table 15.1. The corehole will be continuously sampled using a core barrel with air rotary drilling methods. Marked rock cores shall be stored in standard core boxes, and missing sections of the core shall be replaced with spacers. Up to six samples for analyses of VOCs and inorganics will be obtained from each corehole. Sample depths will be based on field measurement of volatiles (using a photoionization detector), visible contamination or staining, zones of fracturing or secondary porosity features, or intervals of saturation.

The drilling subcontractor shall perform geophysical logging at all new well clusters and video logging in selected boreholes indicated on Table 15.1. Resistivity, spontaneous potential (SP), and caliper logging shall be conducted. As appropriate, gross-count natural gamma ray logging shall also be conducted with both short (8-inch and 16-inch) and long (32-inch and 64-inch) resistivity and SP methods to augment identification and correlation of strata or soil/rock types between boreholes.

At the discretion of CSSA, a total of 51 discrete interval groundwater samples will be collected from up to 13 well locations listed in Table 15.1. As many as five samples per hydrogeologic zone will be obtained using an inflatable packer system. When the formation freely yields groundwater, a pump and/or bailer will be used to purge and collect discrete groundwater samples. When the formation does not freely yield groundwater, the test zone will be purged via air lifting, followed by sample collection with a ¾-inch diameter bailer. The minimum purge volume will be 1.5 pore volumes. Ideally, three to five volumes will be removed before sampling.

Upon completion of well development, dedicated pumps will be purchased and installed within 15 wells. The pumps will be pneumatically-operated bladder pumps consistent with the monitoring system already existing at CSSA. Each pump system will consist of a Teflon™ and stainless steel bladder pump, Teflon-lined tubing, and a lockable wellhead apparatus. As specified in the SOW, low-flow pumps will be installed in all wells listed in Table 15.1.

New dataloggers and transducers will be installed and monitored quarterly at 14 well locations. Each datalogger continuously collects and stores information regarding static water level, water temperature, and conductivity. Telemetry systems are being evaluated for potential implementation at CSSA.

A total of five existing wells will be upgraded or retrofitted to conform to the CSSA groundwater monitoring strategy. The existing wells include two monitoring wells (CS-MW-1-LGR and CS-MW-2-LGR) with an open borehole completion and surface casing. The remaining three wells are older agricultural wells (CS-16, CS-G and CS-H) that require rehabilitation.

Table 15.2 lists the specific tasks for the well upgrades. Specifically, the drilling subcontractor will retrofit existing wells CS-MW-1-LGR and CS-MW-2-LGR with 3-inch ID PVC casing and 25 feet of stainless steel, 0.050-inch wire-wrapped well screen. With exception of the 3-inch well diameter, installation will follow the requirements of the other wells. Well CS-16 will be upgraded with 4-inch ID PVC casing and 25 feet of stainless steel, 0.050-inch wire-wrapped well screen. CS-MW-1-LGR AND CS-MW-2-LGR will be plugged back with bentonite. Well CS-MW-16-LGR will be plugged with 110 feet of grout, and topped off with 11 feet of bentonite to 310 feet bgl.

The existing low-flow bladder pumps will be temporarily removed during the upgrade. If the existing well pads are cracked or otherwise compromised, the pad will be removed and replaced. Well development will follow completion of the upgrade to develop the filter pack and formation. Existing low-flow pumps will require replacement upon completion of the upgrade activities.

Remnants of the old windmill structure and foundation will be removed at Well G. The existing flush-mounted surface casing will require upgrading to a 3-foot stick-up. A new surface completion that includes a 4-foot square pad, locking stick-up protector, and bollard posts will be installed. The well will be re-developed to remove stagnated water, scale, and sediment accumulation. A low flow pump will be purchased and installed in this well.

Table 15.2 - Tasks for Well Upgrades

Re-completion of Well H includes removing the pump from the top of the well and attempting removal of the tubing from the well. If the sucker rods can be removed, the subcontractor shall determine the total depth of the well, install a high capacity submersible pump, and complete the electrical hook-up already present at the well. The submersible pump performance will discharge 20 gallons per minute at a total dynamic head of 350 feet.

If the sucker rods cannot be removed, Well H may be plugged and abandoned and a replacement LGR well drilled at that approximate location when the delivery order is modified to fund such an action.

A total of 22 wells (17 new wells and five upgraded wells) will be developed by the drilling subcontractor using surging, bailing, and pumping techniques. Well development requirements follow the Model Field Sampling Plan (MFSP) AFCEE document.

To prevent sample contamination from the onsite sampling equipment and machinery, decontamination will be conducted using the following procedures outlined in the MFSP. A decontamination pad, large enough to fully contain the equipment to be cleaned, will be set up. One or more layers of heavy plastic sheeting will be used to cover the ground surface. Sampling equipment that comes into direct contact with samples will not be allowed to come into contact with the plastic.

Drill rigs, drill pipe, and other equipment that does not come into contact with the sample medium will be decontaminated with a steam cleaner before initial use and after each borehole is completed. Drill bits will be decontaminated with a steam cleaner prior to use at each boring or monitoring well location. If hot water cleaning alone is found to be ineffective, the equipment may be scrubbed with laboratory-grade detergent, then rinsed with high-pressure steam. All visible dirt, grime, grease, oil, loose paint, etc., will be scrubbed until it has been removed. When possible, drilling will proceed from the "least" to the "most" contaminated sites.

Casing pipe and centralizers will either be certified clean by the manufacturers or if necessary, decontaminated by steam cleaning. Prior to well development, equipment such as pumps or surge blocks will be decontaminated by flushing or pumping laboratory-grade detergent solution, potable water, then ASTM Type II reagent water through the internal components. The exterior of the development pump outlet hose will be steam cleaned.

Sampling equipment includes augers, continuous-core samplers, hand trowels, bailers, pH meters, conductivity meters, shovels, knifes, spatulas, and composition bowls that directly contact samples. This equipment will be cleaned in accordance with the SAP (Volume 1-4: Sampling and Analysis Plan and Quality Assurance Project Plan of the Environmental Encyclopedia).

Investigation-derived waste (IDW) may include soil cuttings, drilling fluids, purged groundwater, well development water, decontamination fluids (water and other fluids), and disposable PPE.

Waste management will include the handling of both drill cuttings and groundwater. The air rotary method will produce a significant volume of drill cuttings and groundwater. It is estimated this effort will produce in excess of 250 cubic yards of drill cuttings, and more than 450,000 gallons of groundwater. Past experience shows that waste management of such large quantities of groundwater with a high solids content to be a significant and costly effort. The solids content and quantity of drilling mud generated has proven to be overwhelming for the low capacity design of the granulated activated carbon (GAC) system. The main problem is the extraordinary storage capacity needed to allow the silt and chalk-sized particles to settle so the water can be decanted. A high yielding borehole can overwhelm 14 storage containers (approximately 60,000 gallons) within 2 days. While the GAC can handle relatively low solids-contaminated purge and development water, Parsons no longer considers the current approach feasible for this long-term project. This includes the significant costs associated with portable storage containers, transportation costs to the GAC, and full-time labor required to treat and dispose of the drilling mud.

CSSA is considering construction of a high-capacity settling/retention basin for the temporary containment of drilling mud produced during the investigation. The basin will be centrally located to serve all drilling locations. The proposed capacity of the pond will be 2,800 cubic yards of drilling mud and water. The pond will be located and constructed where it will not be impacted by runoff. A bermed area will be engineered to mitigate the possibility of runoff to or from the basin. The basin will be lined with a welded plastic liner that seamlessly lines the entire basin area. The area will be fenced to keep livestock and visitors from entering the sites. Drilling mud will be transported to the basin via vacuum truck, where the mud will have ample time to separate and decant. Upon completion of the project, the remaining solids fraction will be characterized for waste determination by VOC and metals analyses. Results of the characterization will determine whether solids will require offsite disposal or remain on-post. Based on previous experience and to reduce costs, it has been assumed for this delivery order that no drilling mud or groundwater will require offsite disposal.

In lieu of a settling basin, another alternative is to utilize multiple transportable 20-yard roll-off boxes placed at each well cluster to contain soil cuttings as necessary. Additional roll-off boxes (covered, lined, and leak-proof) will be placed near the water treatment plant for processing through a GAC unit. Sediment-free groundwater produced during drilling activities and well development, as well as decontamination water, will be transported to this roll-off container via vacuum truck for treatment in the GAC unit. The remaining solids and drill cuttings will be profiled and transported to a permitted landfill. For those solids deemed non-hazardous, CSSA may opt for an alternative recycling or disposal method at CSSA.

15.3 - Quarterly Groundwater Sampling Requirements

Under this task order, a total of seven rounds of quarterly groundwater sampling will occur between March 2002 and September 2003. For the first two events (March 2002 and June 2002), the samples will be collected in conjunction with groundwater sampling already funded under AETC contract task order 5084. Beginning June 2002, this task order will solely fund all quarterly groundwater monitoring and reporting for the CSSA program. As the drilling of new wells progresses and the existing quarterly monitoring under TO 5084 expires, the amount of wells to be sampled increases under this order. By the end of the TO 42 period of performance, a total of 89 wells will have been incorporated into the quarterly monitoring program. The table below indicates the number of wells and sampling parameters to be funded under this contract.

Sampling of the wells will be based on AFCEE Handbook procedures with exceptions as appropriate for the hydrogeology at the site. The wells will be purged in accordance with low-flow sampling techniques. The staff will follow the methods approved in the project’s QAPP and the SAP. QA/QC sampling and analysis will be performed to meet the requirements in the QAPP. The purge water will be containerized and transported for treatment by a GAC treatment system (set up under RL74) prior to discharge at CSSA’s Outfall 002.

15.4 - Analytical Validation and Verification

The analytical validation and verification task includes issues related to analytical data, including audit of the laboratory, oversight of sample collection and submittal efforts, interaction with the selected laboratory, data verification, data validation, and management of electronic analytical data.

The laboratory audit will review the specific analytical methods associated with this project, as well as the overall quality systems utilized by the laboratory. The ability of the laboratory to comply with requirements specified in the AFCEE QAPP and project DQOs will be emphasized. All major and minor audit findings will be documented in an audit report. The laboratory will be required to submit its response and proposed corrective actions for review and approval by AFCEE, CSSA, and Parsons.

Table 15.3 - Sample Quantities and Analytical Parameters

Parsons will oversee each sampling event, including reviewing each Chain-of-Custody (COC) for accuracy and completeness, verifying that the laboratory sample log-in sheets match the COC forms, addressing any sample receipt issues (such as broken sample containers), and maintaining continuous contact with the laboratory regarding scheduling.

Laboratory data packages as specified by percentage in the SOW will be reviewed by Parsons for completeness and adherence to the AFCEE QAPP and the approved laboratory variances. All associated analytical QC data will be examined, and all exceptions will be noted in both the case narrative and data verification report (DVR). The sample results associated with noncompliant QC performance will be qualified in accordance with the AFCEE QAPP Version 3.0. The deliverable will be submitted in accordance with CDRL A041.

Following verification of the laboratory data, the data usability as related to the project DQOs will be assessed. Validation will include examination of historical data (if available), laboratory data trends, and the reasons for data collection. Based on the overall assessment of the data, flags may be removed or changed to reflect usability of the data. The basis for such changes will be detailed in the project summary report.

Electronic data submitted by the laboratories will be loaded into the CSSA GIS database, verified for accuracy, and updated to reflect all data qualifier changes incurred through the data verification and validation process. The data are to be supplied in ERPIMS.

15.5 - Reporting Procedures

A well installation report shall be prepared to document activities associated with installation of the cluster wells. The report shall include boring logs, well completion and development logs, and well design diagrams. The hydrogeologic CSM will be updated with cross sections and associated hydrogeologic diagrams will utilize existing and new data generated from the TO 42 well installations. In addition, five quarterly groundwater reports will be prepared and submitted to document the findings of contaminant concentration and delineation.

The deliverables package will consist of draft and final versions of a field report containing validated analytical data, well construction data, testing results (geophysical and packer), and supporting data appendices produced on a quarterly basis. One well installation report is anticipated (CDRL A024A) rather than several quarterly reports. The appendices will provide the geophysical borehole logs, lithologic logs and construction diagrams, and analytical documentation. Interpretive geology/hydrology discussions and cross sections will be prepared for the CSM update report rather than for the WBS 04 field report. Following a comment/response period after the draft issue of the report, the final document will be incorporated into the CSSA Environmental Encyclopedia (CDRL B020). Data obtained from this task will also be incorporated into the hydrogeologic CSM, and will be submitted in the items of interest report as required by ERPIMS (CDRL B024).

Under another delivery order (Air Mobility Command contract order RL83) Parsons will evaluate available hydrogeologic data concerning the aquifer system under CSSA and prepare a CSM. The CSM will be used to prepare the framework for future basewide numeric groundwater modeling. For this analysis, the specific study area boundaries (a watershed boundary for example) will be established relative to CSSA property, offsite boundary conditions (pumping wells), areas of recharge/discharge (creeks and springs), and major fault and fracture systems. The CSM will be developed to assist in describing groundwater flow patterns and contaminant migration. Funds from this delivery order will be used to update the CSM already in progress.

Specifically, the CSM update will involve the following work elements:

The updated CSM will provide the basic framework and assumptions for future numerical modeling efforts. The deliverables package will consist of updates to the draft and final versions of the CSM report currently under contract (CDRL A039). Following a comment/response period after the draft issue of the report, the final document will be incorporated into the CSSA Environmental Encyclopedia.

All results from these rounds of groundwater sampling will be included in the quarterly groundwater reports (CDRL A024B). Data entered into ERP Tools will be submitted in the items of interest report as required by ERPIMS (CDRL B024). All reports will be prepared as both draft and final versions, with one round of government comments before issuance of the final reports.

From the field efforts covered in this work plan, seven reports will be submitted in draft and final versions. The reports include a technical report detailing well installation and upgrade tasks, as well as an update to the existing CSM, and five quarterly groundwater reports. In addition, all analytical reports will be submitted in accordance with CDRL A041. The project deliverables will be prepared and submitted to the following entities as given in Table 15.5.

It is anticipated that one drilling rig will install the majority of the wells. If available, a second subcontractor drilling rig appropriately sized to competently perform the assigned tasks will also be mobilized. Additionally, a well development crew will begin once the drilling program is well under way. Quarterly groundwater events will be performed in conjunction with other ongoing groundwater sampling events through June 2002. From that point forward, TO42 will fund the quarterly sampling events.

Table 15.5 - Project Deliverables and Distribution List for Well Installation and Quarterly Groundwater Technical Reports

Figure 15.2 provides a tentative timeline for the progression of work. With the current scope of work, it is expected that the drilling and well upgrade efforts will require a minimum of a 14-month field effort. An additional 4 months of report preparation will be needed to complete the well installation and upgrade phase of TO42 through July 2002. Quarterly groundwater reporting will also be completed by July 2003. The schedule will be maintained and updated, and routine submittals will be included in the monthly man-hours and expenditure reports.

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