[Work Plan Index] [Next Section]
AFCEE Contract No. F41624-94-D-8136/0023 - Data Item No. A001a
This addendum provides additional information for the Work Plan for the SWMU Closure Activities at the Camp Stanley Storage Activity (Parsons ES, 1996a), and also the Work Plan for Lower Glen Rose Monitoring Well Installation (Parsons ES, 1996b). Sites B-3 and O-1 are believed to be sources of tetrachloroethene (PCE) and lead contamination found in CSSA well 16. Specific tasks necessary to obtain closure of the sites include the installation of three new 275-foot monitoring wells, the upgrading of two existing wells (well 1 and well 11), and the implementation of a quarterly waste stream sampling and analysis program of fourteen existing wells. Specific guidelines for performing these tasks are presented in this addendum.
Introduction and Background
No changes made.
8.1.1 Installation Description and History
No changes made.
8.1.2 Description of Current Study
8.1.2.1 Project Objectives
No changes made.
8.1.2.2 Scope of Work
Parsons ES will complete the following tasks in order to obtain the necessary data for closure of Sites B-3 and O-1:
Installation of three new 275-foot monitoring wells
The upgrading of two existing wells
The implementation of a quarterly waste stream sampling and analysis program of CSSA water supply and monitoring wells
Environmental Setting
8.2.1 Soils and geology
8.2.1.1 Soils
No changes made.
8.2.1.2 Physiography
No changes made.
8.2.1.3 Geology
No changes made.
8.2.2 Groundwater resources
8.2.2.1 Groundwater Hydrology
No changes made.
8.2.2.2 Groundwater Quality
No changes made.
8.2.3 Surface Water Resources
8.2.3.1 Surface Water Hydrology
No changes made.
8.2.3.2 Surface Water Quality
No changes made.
8.2.4 Meteorology and Climate
No changes made.
8.2.5 Air Quality
No changes made.
8.2.6 Biological Resources
No changes made.
8.2.6.1 Native Vegetation
No changes made.
8.2.6.2 Wildlife and Livestock
No changes made.
8.2.6.3 Endangered, Threatened, and Rare Species
No changes made.
8.2.7 Land Use and demography
No changes made.
8.2.7.1 On Site
No changes made.
8.2.7.2 Off Site
No changes made.
8.2.8 Summary of Previous Investigations at CSSA
No changes made.
SWMU Closure Tasks
No changes made.
8.3.1 Closure Methodology
No changes made.
8.3.1.1 Regulatory Background
No changes made.
8.3.2 Closure Procedures
No changes made.
8.3.3 Field Investigation
8.3.3.1 Background Constituent Levels
No changes made.
8.3.3.2 Field Efforts
Field efforts for this investigations will include the installation of three new 275-foot monitoring wells, the upgrading of two existing wells, and the implementation of a quarterly waste stream sampling and analysis program of CSSA wells.
8.3.3.3 Locating Solid Waste Management Units
No changes made.
8.3.3.4 Geophysical Investigation
No changes made.
8.3.3.5 Field Sampling
No changes made.
8.3.3.6 Sampling Analysis Plan
No changes made.
8.3.3.7 Soil/Rock Borings
No changes made.
8.3.3.8 Groundwater Sampling
No changes made.
8.3.3.9 Data Quality Objectives
No changes made.
8.3.3.10 Soil Gas Survey
No changes made.
8.3.3.11 Quarterly Waste Stream Sampling and Analysis
The groundwater characterization shall be for six quarterly sampling rounds of sampling. Fourteen wells will be sampled during the first two to three quarters. Three new monitoring wells are scheduled to be installed and a total of seventeen wells will be sampled during the final three to four quarters. A summary of the analyses to be performed on the wells is provided in Table 8.3.1.
Wells 2, 3, 4, 16, and D will be sampled by bladder pump following low flow purging. These are the only wells to indicate contamination since quarterly monitoring began.
Wells 1, 9, 10, 11, G, H, and I will be sampled via their existing water production pump. Well 11 has been sampled by a Teflon® bailer since pump removal in December 1995. Well 11 will be sampled by a bladder pump under this addendum.
Wells MW1 and MW2 were installed on April 15, 1996, and will be sampled by a bladder pump.
Groundwater sampling will follow guidelines provided in Section 2.1.5 in the FSP, with the exception of well purging and method of sample collection.
Table 8.3.1 Analyses to be Performed on CSSA Monitor Wells
|
Description |
Analytical Method |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
1 Method to be used is pending regulatory confirmation |
|
Water production wells that are available for groundwater monitoring are purged only to remove water from the pump rods. Aeration resulting from the well pump may drive off VOCs. Samples taken from production wells are intended to identify the presence of contaminants and do not necessarily represent groundwater VOC values. Wells sampled by bailer are not purged prior to sampling. Previously, this action was based upon the assumption that these wells are not cased to depth and thus experience continuous, rapid, open hole lateral flow negating the advantages of purging. Wells with pumps are purged ten minutes prior to sampling. Information used in the decision to not purge the wells in a conventional manner is summarized below:
The CSSA water wells are open borehole from the bottom of the surface casing to total depth. The wells are completed within stable rock formations (limestone or shale) and do not require slotted casing.
The boreholes are open to the Glen Rose Formation (limestone), and in some cases, to the Bexar Shale and the underlying Cow Creek Limestone. These formations are considered to form the middle Trinity aquifer. The average coefficient of transmissivity in the middle Trinity aquifer is 1,700 gallons per day per foot (gpd/ft). Groundwater flow is to the south and southeast estimated at 13.6 to 15.9 feet per year.
Downhole camera surveys have shown that the limestone formations are permeable and fractured in some areas of each surveyed borehole. Water therefore moves freely through the limestone and is most probably not stagnant as found in screened portions of wells completed in shallow, unconsolidated aquifers.
Because the fractured and vuggy limestone should allow fairly free groundwater flow, it has not been necessary to remove stagnant water from the open boreholes.
Total well depths range from 252 to 451 feet bgl.
Footage of total water columns has ranged from 168 to 407 feet in the deepest well (no. 10) and from 1.16 to 116 feet in the shallowest well (no. 4).
Conventional purging would require removal of 3 well bore volumes from each well, resulting in removal of 1 gallon from the shallowest well during a drought, and up to 3,187 gallons from the deepest well during rainy seasons (Summary of Purge Volumes). Removal, characterization, and disposal of any waters containing PCE from open borehole wells that do not appear to contain any stagnant water would cause a significant increase in quarterly groundwater monitoring costs.
Summary of Purge Volumes
|
Well ID |
Casing Dia. (in) |
Total Depth (ft) |
Lowest Water Level (ft-BTOC) |
Highest Water Level (ft-BTOC) |
Lowest Purge Vol. - 3 well bores (gal) |
Highest Purge Vol. - 3 well bores (gal) |
|
1 |
8 |
451 |
201.99 |
105.44 |
1,950 |
2,706 |
|
4 |
2 |
252 |
250.84 |
135.90 |
1 |
56 |
|
10 |
8 |
559 |
390.64 |
152.00 |
1,318 |
3,187 |
|
16 |
6 |
431 |
263.72 |
152.35 |
738 |
1,229 |
Parsons ES, AFCEE, and CSSA have agreed to pursue slow purge and sampling in the attempt to obtain more representative groundwater samples. This technique substantially reduces the volume of purge water produced during sampling, associated costs, and sample turbidity. Slow purge rates typically range from 0.1 to 0.5 l/min, and allow purging of the water in the immediate vicinity to be sampled.
Water level, temperature, pH, and conductivity will be taken prior to and during purging. Well purging will be performed using a low flow bladder pump until temperature, pH, and conductivity values stabilize. Stabilization is defined for pH, as ± 0.1 unit, temperature ± 1°F, and conductivity as ± 5 percent. Successive measurements will be taken at 10 minute intervals. All purge information will be recorded in the field logbook. The pH of the groundwater from each well will be measured using a portable pH meter that is calibrated daily using buffer solutions of the appropriate range for expected values of pH. A pH 7 buffer and either a pH 4 or a pH 10 buffer will be used. The portable field conductivity meter will be calibrated daily using a standard potassium chloride solution. Samples will be taken from the discharge tube of the bladder pump following groundwater parameter stabilization.
8.3.3.12 Upgrades of Two Existing Wells
Well upgrades shall be performed on wells 1 and 11. An upgrade on well 9 may also be performed if field inspections show that it is necessary. Each well upgrade will consist of the installation of new pipe and wiring, installation of an electric line tube and sampling port, and treatment of the well using hydrochloric acid or carbon dioxide (CO2) treatment.
8.3.3.12.1 Installation of New Piping and Wiring
Prior to installing the new piping in wells 1 and 11, the existing piping, pump wiring, and submersible pumps will be removed and placed on 4x4 landscape timbers or equivalent to prevent direct contact with the ground. Piping shall be placed on and covered with impermeable plastic sheeting to prevent excessive weathering. Pump wiring will be wound neatly and placed on and covered with plastic sheeting. Exposed wiring will be wrapped with electrical tape. Submersible pumps will be wrapped in plastic and stored in an upright position.
Approximately 400 feet of flush-threaded steel pipe in 20-foot sections will be installed in the wells. Length of pipe will be determined by the measured water levels and the geophysical logging. The pump wiring will also be replaced if necessary, and rewired to the electrical supply. Items to be replaced will meet specifications provided by CSSA.
8.3.3.12.2 Installation of E-line Tube
A water level measurement tube will be installed in each of the wells as part of the upgrade. The water level measurement tube shall consist of 1-inch, flush threaded PVC pipe advanced from the well seal to 50 feet below top of casing. Water level measurement tubes will be open-ended in the borehole to allow water to enter and have a threaded cap on the other end to allow access for water level measurements. Water level measurement tubes shall be physically attached to the well casing, well seal, or other suitable immobile part to prohibit movement that could result in a change in elevation.
8.3.3.12.3 Carbon Dioxide Treatment
A carbon dioxide treatment will also be performed on wells 1 and 11 to dissolve carbonate minerals and open fractures and voids, increasing the overall hydraulic conductivity of the aquifer, thus increasing well yield.
The Aqua Freed process, developed by ECO2 Solutions, Inc., uses carbonic anhyride gas and carbon dioxide for cleaning wells and increasing yield. A packer is placed in the well above the area of the well that needs rehabilitation. The packer creates a pressure seal to direct carbon dioxide into the well and surrounding formation. Carbon dioxide is then injected through the packer into the well, penetrating the surrounding aquifer. The carbon dioxide reacts with the water, and expands, creates carbonic acid, and freezes water within the aquifer. Minerals encrustation is dissolved and removed from the side of the borehole. The resulting sediment is then removed when the well is redeveloped using air-lift pumping operations.
8.3.4 Solid Waste Management Unit Closure Activities
No changes made.
8.3.4.1 Overview of CSSA Solid Waste Management Units
No changes made.
8.3.4.1.1 General Discussion of Field Activities
No changes made.
8.3.4.1.2 Deep Monitoring Well Installation
Three new 275-foot monitoring wells are scheduled to be installed to provide additional monitoring locations for delineating the contaminant plume and to provide data on the following subjects:
 |
Attitudes and extent of faulting around well 16 |
|
|
Determination if faults act as barriers or conduits |
|
|
Determination of how fault zone affects groundwater gradient and flow direction |
|
|
Direction and rate of migration of contaminant plume |
Installation will follow procedures provided in the Work Plan for Lower Glen Rose Monitoring Well Installation (Parsons ES, 1996b), with the following exceptions:
|
|
Temporary casing will not be installed unless otherwise agreed between CSSA, AFCEE and Parsons ES. Previous well installations indicate that perched water is not typically present. |
|
|
Pilot holes will not be drilled unless otherwise agreed between CSSA, AFCEE, and Parsons ES. |
|
|
Wells will be logged at each change of lithology, not at 0.5 foot intervals. |
|
|
The wells will not be geophysically logged unless otherwise agreed between CSSA, AFCEE, and Parsons ES. |
|
|
No wells will be cored through the saturated zone unless otherwise agreed between CSSA, AFCEE, and Parsons ES. |
Decontamination of drill rigs, drill pipe, casing, centralizers, screen, pumps, surge blocks, and sampling equipment will follow procedures provided in section 1.5 (Parsons ES, 1996b). Handling of investigation-derived wastes (IDW) will follow procedures described in section 1.7 (Parsons ES, 1996c).
8.3.4.2 Low Priority Solid Waste Management Units
8.3.4.2.1 Solid Waste Management Unit B-5
No changes made.
8.3.4.2.2 Solid Waste Management Unit B-6
No changes made.
8.3.4.2.3 Solid Waste Management Unit B-7
No changes made.
8.3.4.2.4 Solid Waste Management Unit B-14
No changes made.
8.3.4.2.5 Solid Waste Management Unit B-22
No changes made.
8.3.4.2.6 Solid Waste Management Unit B-25
No changes made.
8.3.4.2.7 Solid Waste Management Unit B-26
No changes made.
8.3.4.2.8 Coal Bins
No changes made.
8.3.4.3 Medium Priority Solid Waste Management Units
No changes made.
8.3.4.3.1 Solid Waste Management Unit B-1
No changes made.
8.3.4.3.2 Solid Waste Management Unit B-8
No changes made.
8.3.4.3.3 Solid Waste Management Unit B-9
No changes made.
8.3.4.3.4 Solid Waste Management Unit B-12
No changes made.
8.3.4.3.5 Solid Waste Management Unit B-13
No changes made.
8.3.4.3.6 Solid Waste Management Unit B-19
No changes made.
8.3.4.3.7 Solid Waste Management Unit B-27
No changes made.
8.3.4.3.8 Solid Waste Management Unit B-29
No changes made.
8.3.4.3.9 Solid Waste Management Unit B-30
No changes made.
8.3.4.3.10 Solid Waste Management Unit B-31
No changes made.
8.3.4.3.11 Solid Waste Management Unit B-32
No changes made.
8.3.4.3.12 Solid Waste Management Unit B-33
No changes made.
8.3.4.3.13 Solid Waste Management Unit B-34
No changes made.
8.3.4.4 High Priority Solid Waste Management Units
No changes made.
8.3.4.4.1 Solid Waste Management Unit B-10
No changes made.
8.3.4.4.2 Solid Waste Management Unit B-15/16
No changes made.
8.3.4.4.3 Solid Waste Management Unit B-23
No changes made.
8.3.4.4.4 Solid Waste Management Unit B-23A
No changes made.
8.3.4.4.5 Solid Waste Management Unit Building 43
No changes made.
8.3.4.4.6 Solid Waste Management Unit I-1
No changes made.
8.3.4.4.7 Solid Waste Management Unit O-1
No changes made.
8.3.5 Closure Reports and Certifications
No changes made.
Reporting Requirements
No changes made.
Project Schedule
No changes made.