[Table of Contents]

Introduction

This document is an amendment to the existing SAP for the installation of monitoring wells. The purpose of this addendum is to identify the field activities for RL83 and verify that the activities are explained in either the SAP or addenda.

This addendum to the SAP has been prepared in accordance with applicable state regulations for installation, completion and development of monitoring wells.

Field Activities

Field activities to be completed under RL83 include:

1. Installation of four sets of cluster wells containing three wells each.

2. Continuously core and sample the deepest borehole in each cluster.

3. Ensure boreholes are plumb (e.g., perpendicular and vertical) to ground surface using a TOTCO drift indicator tool after every 50 feet of advancement.

4. Perform geophysical logging of the deepest borehole in each cluster.

5. Perform an injection packer hydrologic test in each stratigraphic formation at two intervals per corehole. A total of six tests will be performed at each of the four coreholes.

6. Develop completed monitor wells using surging, bailing, and pumping techniques.

7. Collect and dispose of both liquid and solid investigation derived waste (IDW).

Installation of Cluster Wells

The cluster wells will be installed in each of three units of the Middle Trinity aquifer underlying CSSA. Each well cluster shall consist of a shallow well in the Lower Glen Rose (LGR), a mid-depth well in the Bexar Shale (BS), and a deep well in the Cow Creek (CC) Limestone. All wells will be set with surface casing.

Actual drilling depth will be a function of each well�s location and land surface elevation. Depending on the drilling location at CSSA, up to 40 feet of Upper Glen Rose limestone may also be penetrated. It is estimated that the total drilling depth for the Lower Glen Rose wells are 310 feet; up to 380 feet to completely penetrate the Bexar Shale (70 feet thick), and 450 feet to the base of the Cow Creek Limestone (70 feet thick). The Cow Creek well will be advanced an additional 20 feet into the Hammett Shale (470 feet) for geophysical logging prior to being plugged back to 450 feet for well installation.

Each cluster will be drilled in its entirety before proceeding to the next cluster. The identified procedure for installing each well cluster will follow a phased approach. Protective surface casing will be installed in each borehole prior to proceeding to the next hydrologic unit. Only one wellbore at each cluster will be continuously cored and sampled, which ultimately will become a double triple-cased well monitoring the Cow Creek Limestone. All surface casing will be composed of welded low-carbon steel pipe. The annular seals (grout) will be emplaced via tremie pipe. Wells will be completed with 4-foot square concrete pads with locking well protectors and protector posts in accordance with state regulations. At drilling locations that may be prone to flooding, wells will be flush-mounted surface completions without the use of protector posts. The interior cap in each flush-mounted well will be outfitted with a pressure relief valve. This will prevent the intrusion of surface water into the well, while allowing atmospheric and wellbore pressures to be equilibrated to facilitate easy cap removal.

Before proceeding to the next hydrologic unit, a full decontamination of equipment will take place. A minimum of 24 hours will pass after the emplacement of casing grout before proceeding to the next hydrologic unit. Decontamination will take place between drilling of hydrologic zones or relocating to different well clusters.

The drilling effort will result with single-cased wells in the Lower Glen Rose (310 feet), double-cased wells in the Bexar Shale (380 feet), and triple-cased wells in the Cow Creek Limestone (450 feet). Figure 1 illustrates the well completions for each zone. Welded low-carbon steel protective casing will be installed no more than 5 feet into the underlying formational member. The actual casing depth will be dependent on the nature of the geologic contact. Geophysical data will be key information in identifying the optimum depth to install the casing.

The second string of casing in the Cow Creek well and the primary protective casing in the Lower Glen Rose and Bexar Shale wells will be no larger then 8-inch ID (8-5/8 inch OD) low-carbon steel casing completed within a borehole with a nominal diameter of 12-1/4. This casing completion will result with an annular space of 1-13/16 inches. A minimum of 24 hours will pass after the emplacement of casing grout before proceeding to the next lower hydrologic unit.

The primary protective surface casing on each Cow Creek monitoring well will be no larger than 12-inch ID steel casing completed within a borehole with a nominal diameter of 16-1/4 inches. This casing completion will result with an annular space of 2-1/2 inches. A minimum of 24 hours will pass after the emplacement of casing grout before proceeding to the next lower hydrologic unit.

The actual monitoring well will be constructed as a 4-inch ID well completed within an open borehole no larger than 7-7/8 inches in diameter. The diameter of the wells will allow for the installation of a standard 3.5-inch groundwater pump, which will be sufficiently sized to pump groundwater at that depth.

The interior 4-inch ID 304 stainless steel casing and screen will be installed in each well to limit the amount of open borehole to less than 25 feet. The casing and screen will be centered within the borehole using centralizers at 50-foot intervals. All well casings, screens, and end caps will be flush-threaded, and will not require the use of any glues or solvents. All well material will be certified "clean" by the manufacturer, and will remain within their original packaging until the time of their downhole installation.

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. The annular space will be filled with a 4/10 or 6/9-mesh filter pack from the base of the borehole to height of 2 feet above the top of the screened interval. The filter pack will be emplaced via tremie pipe from the base of the borehole to the top of the designated screened zone. The height of the filter pack will be monitored continuously during emplacement using a weighted measuring tape. Prior to the emplacement of the filter pack, the amount of required filter material will be calculated. Given the well construction parameters (7-7/8 inch borehole and 4-1/2 inch OD screen), approximately 24.5 pounds of sand will be required for each foot of the filter pack height. As an example, a filter pack height of 27 feet will require approximately 660 pounds of 4/10-mesh silica sand.

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 will be dropped into the borehole from the surface, and will settle through the water column by gravity. The bentonite pellets will have a maximum diameter of 3/8-inch, and may be coated "time-release" (TR-30) pellets to prevent their hydration and bridging before settling to their intended depth. 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 mixture will be mixed in the following proportions: 94 pounds of neat Type I Portland or American Petroleum Institute (API) Class A cement, not more than 3 to 5 pounds of 100 percent sodium bentonite powder, and not more than 7 gallons of potable water. A properly mixed batch of grout should yield 10.8 gallons per 94-pound sack of Portland at a density of 14.5 pounds per gallon. This proportion of grout yields approximately 1.45 ft³ per sack of Portland cement. The volume of grout will be calculated prior to its emplacement. The slurry will be injected until grout flows freely at the surface. The annular space will be checked periodically for settlement, and will be topped off as needed. The grout will be allowed to cure for at least 48 hours prior to well development.

Overview of Well Installations

1. Drill/core and sample the corehole using air rotary method until the hole has advanced 20 feet into the Bexar Shale.

2. Log the hole with the geophysical tool.

3. Perform hydrogeologic packer tests at two intervals defined by the geophysical log.

4. Ream the bore hole to 16-1/4 inch diameter and install 12-inch casing from 3 to 5 feet below the Lower Glen Rose Formation / Bexar Shale contact to the surface.

5. Grout the casing and wait at least 24 hours before advancing the boring.

6. Drill/core and sample the corehole until it has advanced 20 feet into the Cow Creek Limestone.

7. Log the hole with the geophysical tool.

8. Perform hydrogeologic packer tests at two intervals defined by the geophysical log.

9. Ream the bore hole to 12-1/4 inch diameter and install 8-5/8 inch casing from 3 to 5 feet below the Bexar Shale / Cow Creek Limestone contact to the surface.

10. Grout the casing and wait at least 24 hours before advancing the boring.

11. Drill/core and sample the borehole until it has advanced 20 feet into the Hammett Shale.

12. Log the hole with the geophysical tool.

13. Perform hydrogeologic packer tests at two intervals defined by the geophysical log.

14. Determine the interval within the Cow Creek Limestone to be monitored by the screened well completion. The production interval will be determined by the results of lithologic and geophysical logging, and will be up to 25 feet long. All the appropriate entities will be consulted (AFCEE, CSSA, and WPI) prior to initiating the well completion.

15. Plug the Hammett Shale portion (or any portion of the Lower Cow Creek as determined by the intended production interval) of the borehole by back filling with coated bentonite pellets. The coating on the pellets provides enough time for the bentonite to settle at the bottom of the borehole before completely hydrating. The depth of the emplaced bentonite will be checked with a weighted tape prior to proceeding with the well installation.

16. Ream the borehole using a 7-7/8-inch bit until the hole has advanced to the predetermined depth of the Cow Creek/Hammett Shale contact, or to the total depth of the intended zone of monitoring (to the top of the bentonite plug).

17. Install 4-inch stainless steel casing and screen to monitor a maximum of 25 feet of the hydrologic interval. Well construction will be in accordance with the design and specifications previously described.

1. Drill borehole using air rotary method until the hole has advanced 3 to 5 feet below the predetermined depth of the Lower Glen Rose Formation / Bexar Shale contact.

2. Ream the borehole to 12-1/4 inch diameter and install 8-inch casing from 3 to 5 feet below the Lower Glen Rose Formation / Bexar Shale contact to the surface.

3. Grout the casing and wait at least 24 hours before advancing the boring.

4. Drill borehole until it has advanced to the predetermined depth of the Bexar Shale / Cow Creek Limestone contact using a 7-7/8 inch drill bit, or to the total depth of the intended zone of monitoring.

5. Install 4-inch stainless steel casing and screen to monitor a maximum of 25 feet of the hydrologic interval. Well construction will be in accordance with the design and specifications previously described.

1. Drill borehole until it has advanced to the predetermined depth of the Lower Glen Rose Formation / Bexar Shale contact or other intended zone of monitoring using a 7-7/8 inch drill bit.

2. Install 4-inch stainless steel casing and screen to monitor a maximum of 25 feet of the hydrologic interval.  Well construction will be in accordance with the design and specifications previously described.

Contingency Planning

Inevitably, unforeseen contingencies will arise which will require deviations or modifications to the SAP. Some events may require immediate action, while others may be less severe and can be handled in a roundtable fashion with CSSA, AFCEE, WPI, EPA, and the TNRCC. While it is not possible to predict all unexpected field conditions, two scenarios are worthy of discussion: contaminated perched groundwater and encountering dense non-aqueous phase liquids (DNAPLs).

As a daily procedure, the borehole will be monitored before commencing drilling activities for the accumulation of groundwater or DNAPLs. Groundwater accumulation will be measured using either an electric level measuring device, a weighted surveying tape, or a Teflon� bailer. If perched groundwater is encountered or accumulated, an attempt will be made to obtain a representative grab sample of the groundwater. When perched water is encountered and a sample obtained, CSSA will be notified. CSSA may opt to have the sample screened by a local laboratory (contracted independently by CSSA) before drilling resumes. Any decisions based upon contaminant screening would require immediate analyses to avoid excessive drilling standby time. Factors that may affect the decision to analyze perched water may include evidence of contamination in the retrieved core, or proximity to potential source areas.

Past experience in the South Pasture area (installation of wells MW1 and MW2) indicated that perched groundwater was not present in that locality. However, this may not be consistent for all the drilling locations, and will likely be related to the amount of recent precipitation. Not withstanding the primary surface casing, no provisions are provided in the basic SOW and cost estimate for additional or temporary casings. During the coring of the pilot holes, temporary casing may be prudent to seal off perched zones since borehole advancement is significantly slower than the remainder of the drilling. Temporary casings could be installed by those methods described in the Work Plan for Lower Glen Rose Monitoring Well Installation (Parsons ES, 1996), which utilizes a small diameter surface casing temporarily emplaced with a bentonite seal. The temporary casing would be removed prior to the installation of the larger diameter permanent steel casing. Such actions will require a field modification to the SOW.

Additional permanent surface casings for the Lower Glen Rose and Bexar Shale wells could be completed with the same rig planned for the drilling project at an increased cost. Any additional surface casing on those wells would result in a well with similar construction to the Cow Creek well shown in Figure 1. To install an additional string of surface casing on the Cow Creek well, a foundation drilling rig may be needed to drill the required diameter hole in excess of 20 inches. The additional costs and overall practicality would need to be seriously considered by all parties involved before attempting such an endeavor.

A clear Teflon bailer will also be used to check the bottom of the borehole for the accumulation of DNAPLs. If the daily borehole monitoring indicates the presence of DNAPLs, all drilling activities will be immediately suspended, and CSSA and AFCEE notified. CSSA will be responsible for the notification of both the EPA and TNRCC of the presence of DNAPLs. At that time the decision will be made whether to abandon the borehole, or complete the well at that depth.

Core Sample Collection

The deepest hole in each cluster will be drilled first and referred to as the "corehole". The corehole will be continuously sampled using a core barrel with air rotary drilling methods. Every reasonable attempt will be made to recover the correct orientation of the core samples. This will be accomplished by the following:

1. Stake a spot on the ground near the corehole and note the bearing from the corehole to the stake.

2. Mark the inner barrel (split spoon) along the bearing between the corehole and the stake.

3. After drilling, note orientation of mark on inner core barrel.

4. Mark the core sample with chalk or by scoring so that it corresponds with the mark on the outside of the inner core barrel. Marked rock cores shall be stored in standard core boxes, and missing sections of the core shall be replaced with spacers.

CSSA will supply core boxes, and Parsons ES will label them appropriately with date, time, depth, and drilling information relevant to the retained sample. Each section of core will be marked with a corresponding depth, and electronically recorded using the CSSA digital camera. The retained core will be prepared for storage and archival at the University of Texas-San Antonio core library.

Sample Analysis

Up to 20 feet of core will be submitted from each corehole for fracture analysis at an offsite laboratory. The intervals will be determined after review of downhole geophysical interpretations to determine the zones of interest. The remaining core samples will be placed in sturdy core containers for archival and future re-evaluation as necessary.

A total of six samples (one surface sample and five subsurface samples) for volatile organic compounds (VOCs) and inorganic analyses will be obtained from each of the four coreholes (Table 1). Sample depths will be based on field measurement of volatiles (using a photoionization detector), visible contamination or staining, zones of fracturing, secondary porosity features, or intervals of saturation. One groundwater grab sample will be obtained from each hydrologic zone for background metals and aqueous cations/anions prior to casing the corehole (Table 2). All environmental samples will be collected in accordance with those procedures defined in Section 2, Section 3, and Section 4 of the Sampling and Analysis Plan.

Table 1 - Sampling Parameters from Soil/Rock Samples

Table 2. Sampling Parameters for Groundwater Grab Samples

TOTCO Vertical Drift Indicator

A single shot declination tool will be used to check the plumbness and straightness of the boreholes and monitoring wells. The declination tool will be run in the borehole after every 50 feet of advancement. All monitor wells shall be plumb within two degrees of vertical where the water level is greater than 30 feet below land surface unless otherwise approved by AFCEE. Monitor wells not meeting straightness or plumbness specifications shall be redrilled and/or reconstructed.

The device is lowered into the borehole through the drill pipe on a cable line. A mechanical timer within the device controls a punch, which perforates a small circular chart. The chart consists of concentric circles in a "bulls eye" pattern radiating from the center. The chart is perforated near the center if the hole is true vertical or off-center in the concentric circle that indicates the degree of deviation from true vertical. A second perforation is made a few seconds after the first one. If the two perforations indicate the same deviation, the record is accurate. If they vary, another set of readings should be taken because they are not correct. Different charts indicating different degree values are available for the device.

Borehole geophysical techniques employed for this project include resistivity (both short [16-inch] and long [64-inch]), spontaneous potential (SP), natural gamma ray, and caliper logging. Some of the theory and general procedures for borehole geophysical techniques are described in Groundwater and Wells, Fletcher G. Driscoll, 1986; others can be found in any borehole geophysical text.

Geophysical logging will be performed in boreholes to identify soil/rock types before surface casing is installed and injection packer tests are performed. Resistivity, SP, and caliper logging are typically conducted in pilot boreholes drilled with mud, air, or water. Gross-count natural gamma ray logging may also be conducted with resistivity and SP methods to augment identification and correlation of strata or soil/rock types between boreholes.

The borehole geophysical logging shall be conducted by a qualified individual and supervised by the onsite Parsons ES geologist. Downhole geophysical tools, cables, probes, and other equipment will be decontaminated before and after being lowered into a borehole. For each geophysical tool, calibration data and scale parameters will be verified before logging begins and will be documented for each borehole. Geophysical data are stored in hard-copy and electronic formats. After logging, a reproducible copy of the field strip-chart log with a heading specifying project, borehole number, location and depth, geophysical equipment types, and equipment settings shall be maintained in the project file.

General requirements for borehole geophysical surveys are: (1) all downhole equipment shall be decontaminated according to the specification of this SAP; (2) borehole measurements shall be recorded both going into the hole and coming out of the hole; (3) paper copies of curves generated from each logging run shall show all the curves at the scale of 1 inch equals 20 feet; and each paper log shall indicate the location of the well, date of log acquisition, type of survey instrument, and a list of other instruments used in that borehole; and interpretations shall be annotated on the margins of paper log records; (4) all logs shall be referenced to a measuring point notched in the surface casing or to ground level if the well is not cased; (5) radioactive sources or devices shall not be used unless they are explicitly called for in the statement of work (SOW) and; (6) adverse borehole conditions shall be reported in the field log.

Electrical resistivity logging is conducted in conjunction with SP logging. When used together, these methods are commonly referred to as electric or "E" logs.

The normal resistivity tool uses two electrodes to aid in the correlation of stratigraphic layers. A 16-inch separation of the electrodes is used during the logging of the coreholes for the short normal log, and a 64-inch separation is used for the long normal. The larger spacing delivers deeper penetration but lower bed resolution. Silt, clay and shale typically have low resistivity while sandstone and limestone saturated with fresh water have the highest resistivity values.

The spontaneous potential tool records the electrical potential produced by the interaction of formation water, conductive drilling fluids, and certain ion-selective sediments. Although the spontaneous potential curve is not a measurement of permeability, a deflection is generated when permeable formations come in contact with the drilling fluids, and a baseline curve (no response) is formed when a nonpermeable formation (shale or clay) is encountered. Individual bed boundaries and thickness can be differentiated on the curve, making stratigraphic correlation more accurate and representative.

Resistivity and SP are simultaneously measured from the bottom of the hole upward. The measuring instruments shall be raised toward the surface at a rate no greater than 10 feet per minute. Monitor well screen depths are selected in the field based on interpretation of the strip-chart log. Equivalent measurement scales increase the accuracy of geologic interpretation in the field and, therefore, screen interval selection.

The scales selected for portraying resistivity or SP readings shall be the same at all boreholes. The appropriate scale is determined in the field by conducting offset logs prior to the final survey. Offset logs are a quality assurance and calibration step that involves logging an upper or lower portion of the borehole and adjusting the log response to obtain the optimum scale. Scales to be adjusted are the horizontal (millivolts for SP and ohm-meters for resistivity) and vertical (feet). The resistivity logs shall consist of the short-normal (16-inch) and long-normal (64-inch) configurations.

Natural gamma ray logging is used to estimate lithologic characteristics of geologic formations by recording gamma radiation emissions. The gamma ray logging tool contains one or more scintillation detectors which measure the natural radioactivity in soil layers adjacent to the borehole. Gamma logging may be used in conjunction with SP, resistivity, and caliper logs in fluid-filled boreholes. This technique allows logging through the casing or the well pipe after well construction; however, the radiation measurements are attenuated by well casing. Because radioactive elements tend to concentrate in clays and shales, the log normally reflects the shale content of the formations. Clean formations such as sands, usually have a very low level of radioactivity.

Caliper logs measure the variations in the borehole diameter. A caliper, a spring-loaded mechanical device with one to four adjustable arms that press against the borehole wall, measures the diameter in cased and uncased boreholes. Variations in the borehole diameter, factors such as borehole erosion (washout), the presence of swelling clays or resistant strata, and the volume of filter pack or grout needed for well completion, are determined. Caliper logs are conducted by lowering the device to the bottom of the borehole and recording the measurements as the caliper is raised.

Packer Test Procedures

Injection packer testing will be performed in each hydrologic zone at two intervals for a total of 6 tests per corehole. The zones will be determined from the lithologic core and down hole geophysical results. A packer consists of a rubber sleeve, which expands against the wall of the borehole when pressure is applied to it. The testing of isolated sections of a borehole requires the use of 2 pneumatic isolation packers separated by a length of perforated pipe. The double-packer assembly and inflating line are then lowered into the borehole on a string of pipe so that the perforated section is opposite the interval to be tested. Figure 2 illustrates a typical packer test design.

Prior to each packer test a check should be made to insure that the injection tubing is completely filled with water. The packers should be inflated initially with the valves open. The line valve should then be closed, and the pump started with the recirculation valve open. To initiate the test the line valve is opened and the recirculation valve closed simultaneously.

At the rates of fluid injection anticipated in the tests, it may be difficult to maintain either a constant rate of injection or a constant injection pressure during field operations. It is therefore imperative that both pressure and injection rate be measured and recorded versus time throughout the test. Measurements should be made as frequently as possible during the early moments of the test.

If injection rates are very small, injection volume should be monitored using a manometer connected to the top of the storage tank. As necessary, water may be added at intervals to the tank to keep the water level above the top of the tank. When water is added, the time and the resulting increase in water level in the manometer should be noted. If injection rates are somewhat higher, it may not be practical to keep the water level above the top of the tank; in this case, water level can be allowed to lower in the tank, and the injection rate may be monitored using a manometer connected to the base of the tank. In either of these cases, flow meter readings should also be taken to supplement manometer readings. Finally, if high injection rates are encountered so that water must be admitted continuously to the tank, during the test the injection rate should be monitored using the flow meter alone. As with the pressure readings, as high a frequency of measurement as possible should be used during the early minutes of the test.

The period of injection should continue for one hour. As the time of injection continues, changes in pressure and in injection rate will occur more slowly and frequency of measurement may be decreased. However, measurement should be taken at least every five minutes until the end of the injection period.

Pumping times and pressures depend on the depth and requirements of the test and the nature of the materials being tested. As far as the length of time to run the test is concerned, the general rule is to run the test until an equilibrium condition is established. This is considered to have been reached when four or five readings of pressure and flow taken at approximately 5-minute intervals are essentially constant.

The hole must be cleaned of all cuttings and drilling mud (if used) prior to testing. Appendix A provides worksheet for monitoring the injection system and calculating the results of the packer tests.

The spacing of packers (which governs the length of the test section) is generally between five and 10 feet apart, depending on the diameter of the hole. The minimum spacing of packers should be governed by the following guideline:

S_p/D > 5

Where:

S_p = the spacing, or length between packers, and

D = the diameter of the borehole.

Permeability is calculated from the following formulas:

For the unsaturated zone (Zone 1) above the water table: K = Q/C_u*r*H

For the saturated zone (Zone 2) above the water table: K = 2Q/(C_s*r)(T_u+H-A)

For the saturated zone (Zone 3) below the water table: K = Q/C_s*r*H

Where:

K = Permeability (ft/sec)

Q = Flow (cubic ft/sec)

A = Length of test section (ft)

r = Radius of the test hole (ft)

C_u = Conductivity coefficient for unsaturated materials with partially penetrating cylindrical test wells (obtained from Chart A in Appendix A).

C_s = Conductivity coefficient for semi-spherical flow in saturated materials with partially penetrating cylindrical test wells (obtained from Chart B from Appendix A).

T_u = Distance in feet from the water surface in the well to the water table;

(T_u = b_u-D+H) where:

b_u = Thickness of unsaturated material (ft)

D = Distance from the ground surface to the bottom of the test section (ft)

H = Effective head in feet (h₁ + h₂ � L) where:

h₁ = (above the water table) distance between the Bourdon gauge and the upper-surface of the lower packer (ft)

h₁ = (below water table) distance between the gauge and the water table (ft)

h₂ = Applied pressure at the gauge (1 psi = 2.307 ft of head)

L = Head loss in feet due to friction: L = 10.44*P_L*Q^1.85/c^1.85*d^4.865)

P_L = Length of drill pipe (feet)

Q = Flow (gal/min)

c = 140 (Pipe surface roughness coefficient)

d = Diameter of pipe (in)

For these equations to be valid, the thickness of each packer must be > 10 times the radius of the test hole.

Monitoring Well Development

Each well will be developed by the drilling contractors using surging, bailing, and pumping techniques. The well development requirements follow the MFSP AFCEE document. The monitor well development requirements are: (1) all newly installed monitor wells shall be developed no sooner than 48 hours after installation to allow for grout curing, (2) all drilling fluids used during well construction shall be removed during development, (3) wells shall be developed using surge blocks and bailers or pumps (prior approval for any alternate method shall be obtained, in writing, from AFCEE before well construction begins), and wells shall be developed until: (a) the suspended sediment content of the water is less than 0.75 mL/L, as measured in an Imhoff cone according to method E160.5; (b) the turbidity remains within a 10 nephelometric turbidity unit range for at least 30 minutes; and (c) the stabilization criteria are met: temperature � 1oC, pH � 0.1 units, and electrical conductivity � 5 percent, (4) discharge water color and volume shall be documented, (5) no sediment shall remain in the bottom of the well, (6) no detergents, soaps, acids, bleaches, or other additives shall be used to develop a well, and (7) all development equipment shall be decontaminated according to the specifications of the following section.

Decontamination Procedures

All equipment that may directly or indirectly contact samples shall be decontaminated in a designated decontamination area. This includes casing, drill bits, drilling rods, auger flights, the portions of drill rigs that stand above boreholes, sampling devices, and instruments, such as slugs and sounders. In addition, the contractor shall take care to prevent the sample from coming into contact with potentially contaminating substances, such as tape, oil, engine exhaust, corroded surfaces, and dirt.

The following procedure shall be used to decontaminate large pieces of equipment, such as casings, drill bits, pipe and rods, and those portions of the drill rig that may stand directly over a boring or well location or that come into contact with casing, auger flights, pipe, or rods. The external surfaces of equipment shall be washed with high-pressure hot water, and if necessary, scrubbed until all visible dirt, grime, grease, oil, loose paint, rust flakes, etc., have been removed. The equipment shall then be rinsed with potable water. The inside surfaces of casing, drill rod, and auger flights shall also be washed as described.

The following procedure shall be used to decontaminate sampling and drilling devices, such as split spoons, core barrels, and bailers that can be hand-manipulated. For sampling and smaller drilling devices, scrub the equipment with a solution of potable water and Alconox, or equivalent laboratory-grade detergent. Then rinse the equipment with copious quantities of potable water followed by a ASTM Type II Reagent Water. (If equipment has come in contact with oil or grease, rinse the equipment with pesticide-grade methanol followed by with pesticide-grade hexane.) Air dry the equipment on a clean surface or rack, such as Teflon, stainless steel, or oil-free aluminum elevated at least two feet above ground. If the sampling device shall not be used immediately after being decontaminated, it shall be wrapped in oil-free aluminum foil, or placed it in a closed stainless steel, glass, or Teflon container.

Reagent-Grade II Water, methanol, and hexane shall be purchased, stored, and dispensed only in glass, stainless steel, or Teflon containers. These containers shall have Teflon caps or cap liners. It is the contractor's responsibility to assure these materials remain free of contaminants. If any question of purity exists, new materials shall be used.

A full decontamination of equipment will take place between hydrologic zones and relocating to different well clusters. To prevent sample contamination from the onsite sampling equipment and machinery, decontamination will be conducted using the following procedures. 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 will come into direct contact with samples will not be allowed to come in 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 the 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, grim, 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.

The casing, centralizers, and screen will either be certified clean by the manufacturers or will be decontaminated by steam cleaning.

Prior to well development, equipment such as pumps on surge blocks will be decontaminated by flushing or pumping laboratory-grade detergent solution, potable water, then ASTM Type II Reagent water (Reagent Grade II water) through the internal components in the order listed below. The exterior of the pump inlet 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. The following steps must be followed when decontaminating this equipment:

1. Set up a decontamination area at the site. The decontamination are should progress from "dirty" to "clean" and end with an area for drying decontaminated equipment. At a minimum, clean plastic sheeting must be used to cover the ground, tables, or other surfaces on which decontaminated equipment is to be placed. However, sampling equipment to be used for organic sample collection shall not come in contact with plastic after the final rinse; oil-free aluminum foil must be used. Plastic sheeting must also be placed to capture Reagent-Grade II water, hexane, and methanol used for rinsing equipment.

2. Wash the item thoroughly with soapy, laboratory-grade detergent solution. Do not submerge pH meters or conductivity meters. Use a stiff-bristle brush to dislodge any clinging dirt. Disassemble any items that might trap contaminants internally before washing. Do not reassemble until decontamination is complete, and items are dry.

3. Rinse the item in clear potable water. Rinse water should be replaced as needed, generally when cloudy.

4. Rinse the item with ASTM Type II Reagent water.

5. Rinse equipment with pesticide grade methanol.

6. Rinse equipment with pesticide grade hexane.

7. After drying, wrap the cleaned item in oil-free aluminum foil for storage at least 2 feet above the ground.

8. After decontamination activities are completed, collect disposable gloves, boots, and clothing. Place contaminated items in proper containers for disposal.

Investigation-Derived Waste Handling

Waste management will include the handling of both drill cuttings and groundwater. Air rotary method will produce a significant volume of drill cuttings and groundwater. One transportable 20-yard rolloff box will be placed at each well cluster to contain soil cuttings. An additional rolloff box (covered, lined, and leak-proof) will be placed near the water treatment plant for processing through a granular activated carbon (GAC) unit. Groundwater produced during the drilling activities and well development, as well as decontamination water will be transported to this rolloff container via suction truck for the settlement of suspended solids. The resulting supernatant fluids will be pumped off the top for treatment in the GAC unit. It is assumed that TNRCC approval of discharge from the GAC unit will be obtained by the time the wells are developed. The remaining solids and drill cuttings will be profiled using TCLP analyses, and transported to a permitted landfill (Class 1 or Class 2 depending on analytical results). For those solids that are deemed non-hazardous, CSSA may opt for an alternative recycling or disposal method at CSSA.