NCD980602163_19920625_Warren County PCB Landfill_SERB C_Alternatives and Procedures for Evacuating Rainfall from PCB Landfill-OCR

James G. Martin, Governor
William W. Cobey, Jr., Secretary
June 25, 1992
RE: Alternatives and Procedures for Evacuating Rainfall from
the Warren County PCB Waste Disposal Facility Located in
Warren County, N.C.
Project Number
Gentlemen:
William L. Meyer
Director
On June 15, 1991 the N.C. Department of Administration informed the DEHNR that the
responsibility of technical assistance for management of the landfill was transferred to the
Division of Solid Waste Management. On June 25, 1991 the PCB landfill was inspected and
water level monitoring within the 6" PVC Leachate Collection Pipe, located within the landfill
was performed by the Division of Solid Waste Management Personnel. It was noted that a water
level of 14.17' existed within the landfill at this time. Monitoring of the water level within the
landfill continued for approximately 1 year with fluctuation in the water level ranging from
14.17 to 12.92 feet (l '-3") from the top of the leachate collection pipe.
Pumping of the existing leachate collection system was performed by Division of Solid Waste
Management personnel in August of 1991. It was determined that the current generator powered
pumping system (Bladder pump) will evacuate 120 gallons of water per cycle with a recharge
rate of 2 hours 45 minutes. The effluent water from the landfill was sampled and tested for PCB
concentration and resulted in no detectable levels at this time.
Based on the pumping and recovery rate of the landfill water it was estimated that it would take
10 to 12 weeks to pump down 1 foot of head on the landfill water.
The existing landfill design, construction, groundwater and landfill water level history was
evaluated to help determine the source of the existing landfill water. The results of this
evaluation is included in the appendix to this report for your reference.
In summary, the presence of the water within the landfill appears to be the remaining rainwater
and dust retardant water that existed at the close-out of the landfill in 1983. Pumping of the
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leachate collection system began shortly after close-out of the landfill on March 7, 1983. This
pumping process was performed as a final condition to the contract in order to remove the
remaining rainwater that accumulated during the operational phase of the project. Pumping of
the leachate collection system was completed on June 1, 1983. It is expected that the slow
recovery rate of the water level in the leachate collection system indicated to the contractor that
the evacuation was complete. However, based on the site evaluation and analysis performed by
the Division of Solid Waste Management, it appears that approximately 1 to 1.5 million gallons
of additional rainwater remains within the landfill. Based on the slow recovery rate previously
encountered in the landfill leachate collection system, it appears that an additional evacuation
and treatment system may take 1 to greater than 5 years to complete at a recovery rate of 1 to
3 GPM. This time frame may be more precisely determined after the Evacuation System is
installed and in operation for several months .
The following alternatives are recommended for the evacuation of the remaining groundwater
from the landfill;
1. Use existing (1 V : 3H) sloped leachate collection pipe system with a special
submersible pump system designed or modified to operate in the sloped pipe system to
remove the water from the landfill. A sample-storage parallel tank system must be
constructed in order to meet the Regulatory requirements for testing and disposal of the
water
2. Design a boring through the top layer of the landfill and the PCB contaminated soils
to a depth just above the upper liner and construct a vertical extraction well with a
sample-storage parallel tank system to remove the water from the landfill
3. Seek EPA approval to leave the water in landfill as long as the lower leachate
collection system remains dry
Alternative #1 is the most economical and practicable alternative if evacuation of the landfill is
imperative. Therefore, it is recommended that Alternative #1 be initially utilized to remove the
water from the landfill. Alternative #1 will also eliminate penetration of the top liner membrane,
minimizing exposure to PCB' s.
If alternative #3 is not a viable alternative and uncertainties about rainwater infiltration and
leakage of the landfill liner systems exists after completing alternative #1 or if alternative #1 is
not effective for evacuation of the landfill water, then alternative #2 should be reconsidered and
initiated. Alternative #2 will include soil classification and delineation and water level data
within the landfill during the well installation process. Testing of the recovered soil samples
may also be performed at this time in order to evaluate the stability or half life progress of the
PCB' s over time.
Alternatives #1 & 2 will require a minimum of 3 holding tanks and a activated carbon filter
system in order to test and treat any effluent having PCB concentrations greater than 1.0 part
per trillion (or detection limits 1.0 ppb) which meets the EPA drinking water standards at this
time.
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PRELlMINARY INSTALLATION REQUIREMENTS
The following 2 steps are required prior to initiation of Alternatives 1 & 2;
-Set-up pennanent electricity on site
-Establish Known USGS bench mark elevations on site
WELL INSTALLATION PROCEDURES
Altematve # 2
The soil boring for the well installation should be perfonned with a truck or A TV mounted
auger drilling rig, which utilizes continuous flight augers to advance the borehole. Drilling fluid
should not be used in this process.
Split-spoon samples should be obtained by means of the split-barrel sampling procedure in
general accordance with ASTM specification D-1586 at 5 foot intervals starting at 25' below the
landfill surface and on a continuous basis from 33.5 feet to 39.0 feet or to the tennination depth
below the existing landfill surface. The soil boring should extend into the N.C. DOT 2s sand
filter blanket approximately nine (9) inches and should not penetrate the underlying lower clay
liner more than three (3) inches. This is a critical aspect of the work.
WELL CONSTRUCTION
The vertical well should be placed near the bottom of the nine (9) inch sand blanket. Extreme
Care should be taken during drilling and well installation not to penetrate the impenneable clay
liner. A sand pack must then be placed around the well to a minimum of 12 inches above the
screened section of the well. The sand pack should be graded to match the 0.010 inch screen
slot. the remaining annular space around the well standpipe may be back-filled with the
containerized PCB contaminated soils or an approved borrow material to a depth of
approximately 6 feet below the landfill surface. The remaining 6 feet of annular space should
be grouted to the 10 mil top liner. For details of well construction see the well installation
diagram in the appendix. All well construction materials should be on site at the beginning of
drilling operations and well construction should be perfonned in a timely manner with no delays
between drilling and well installation other than overnight if required.
LINER REPLACEMENT
After the grout hardens the topsoil and cover layer should be removed to expose approximately
6 feet square of the 10 mil PVC liner surface (approx. 2 feet deep). The liner surface should
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be thoroughly cleaned and dried prior to patching with a similar 10 mil liner material having an
overlap of 16 inches in all directions. The liner patch should be certified by a representative of
the liner supplier prior to back-filling with 1 foot of bridging material and 1 foot of topsoil.
After the 10 mil liner patch is approved the bridging or cover material and topsoil may be placed
in 6 inch lifts to the top of the landfill surface. Each six (6) inch lift should be compacted with
a small vibratory compactor or whacker in general accordance with AS1M D-698 standard
proctor method. A flush mounted protective metal cover should then be installed at the surface
and set in concrete. For details of the liner replacement and the flush mounted protective cover,
see the liner repair detail and well construction diagrams included in the appendix.
PCB CONTAMINATED SOIL CUTIINGS
All soil cuttings should be stored in 50 gallon drums with markings in accordance with 40 CFR
761.45 for transport to an EPA approved chemical waste landfill or incineration facility or
replaced as back-fill in the annular space around the well at the subject PCB landfill. Storage
of PCB contaminated cuttings in covered fifty (50) gallon drums will also eliminate transport of
PCB contaminated soil particles by rain and airborne dust. These containers should be on site
prior to the start of drilling operations.
QUALITY CONTROL
A quality control (QC) professional familiar with well construction procedures and the
Hazardous and Solid Waste Management laws shall be provided by the state or a consulting firm
on-site during all operations to provide and assure conformance with the details of the plans and
specifications. Such assurance shall be furnished to the Regional Administrator at the
completion of the project with associated well construction records and affidavits for the PVC
liner patch certification and the transport and disposal facilities for the PCB contaminated soil
cuttings.
HEALTH AND SAFETY CONSIDERATIONS
Due to the uncertainties of long term effects of human exposure to low levels of PCB's, all
drilling and QC personnel present during drilling operations, are required to wear protective
clothing (TYVEK coveralls, rubber gloves and rubber boots) and respirators. All work
involving exposure to PCB contaminated soil must be performed in general conformance with
OSHA 3021 and 1910.34 and 29 CFR 1910.120 and 1910.34.
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EVACUATION PROCEDURES
PUMPS AND HOLDING TANKS
Alternatives 1 and 2 will utilize pumping of the landfill leachate collection system to remove
rainwater and dust suppression water that accumulated or was utilized during the operational
phase of excavation, transport and back-filling of the landfill with the PCB contaminated soils.
If alternative #1 is used the submersible pump for the project should be placed in a sand screen
filter with rubber torque arresters around the screen to buffer start-up oscillation. The pump will
then be lowered initially to a depth of approximately six (6) feet from the bottom (lower at 2
foot intervals to the bottom or as required) of the six (6) inch diameter PVC leachate collection
pipe (3 HORIZ. to 1 VERT. slope).
The landfill water will then be pumped into the primary holding tank. When the primary storage
tank is full, the system must be designed to automatically switch over to the secondary tank in
order to maintain 24 hour continuous pumping operations. However, a back-up system designed
to shut off all electrical power to the pump should be installed. This shutdown of the system
should be initiated in the case where both tanks are full or for pumping system blockage or
failure.
Use (Myres) 2 inch submersible pump with variable pumping capacity of 1 to 9 gallons per
minute (GPM) or an equivalent pump with similar variable pumping capacity. The pump must
also be resistant to scour from sand and sediment in the ground water. The Pump may need to
be submerged in sediment as the landfill is evacuated and the pump is required to be lowered
to the bottom of the collection pipe and sump pit.
SYSTEM START-UP
A private contractor should be hired to initially set-up the most efficient pumping rate and
disposal-storage sequence for the landfill water evacuation system. This work should be
monitored and assisted on site by a quality control professional with the state Division of Solid
Waste Management, who is familiar with the requirements of the system. This quality control
professional will also be responsible for setting-up the sampling and testing of the water in the
appropriate standby tank with a private laboratory on a weekly or bi-weekly basis or as often
as the pumping and recovery rate will allow. Proper disposal of the water after testing should
also be controlled or performed at this level. The private contractor responsible for system start-
up will also be required to be on call for periodic maintenance and adjustment of the system as
required.
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HOLDING TANKS
Three (3) 10000 gallon water storage tanks will be utilized to store, sample and filter water
pumped from the leachate collection system prior to disposal.
The tank system will consist of three (3) 10000 gallon carbon steel above ground storage tanks
with a minimum of two (2) bottom drain fittings (2 ti or larger) and 2 top fill connections (2 ti or
larger). A small bottom nozzle with a control valve for obtaining laboratory test samples should
also be installed on each tank. The primary and secondary tanks will operate in parallel so that
pumping operations may be performed on a continuous basis and testing of water in alternate
tanks may be performed systematically (weekly or bi-weekly) depending on the landfill water
recovery rate (3 gallons per minute max.).
Carbon filter units may be utilized to remove PCB contaminants from the landfill water after
extraction and testing if required. A third 10000 gallon tank may be utilized as required to store
filtrate from the activated carbon filters for retesting prior to disposal. The third tank is optional
based on the NPDES Permitting requirements for the prefilter and carbon filter treatment and
release process.
CONTAINMENT AREA
The three (3) 10000 gallon above ground storage tanks are to be installed on tank piers and
saddles within a 30 ft. X 45 ft. concrete slab with rebar on 12 inch centers. A Four (4) feet
high concrete block wall with rebar and cored with 2000 PSI concrete will be used around the
perimeter of the slab with water tight caulking for containment. A six (6) foot high 9 gauge
chain link fence with three (3) strand barb wire top and three (3) foot personnel gate is required
for security. Nine (9) cast-in-place concrete above ground tank piers for tank saddles must also
be installed. Fine grading of the site, forming and placement of the base stone will be included
in this phase of the work.
ACTIVATED CARBON FILTER
Temporary Carbon Filter Diaphragms must be available on site at the start of pumping and
storage of the landfill water. The carbon filter units should be capable of filtering low level
PCB contaminated water at a sufficient rate to allow the most efficient testing and disposal
schedule for contaminated landfill water (10 to 50 gallons per minute). Due to the turbidity of
the landfill water during pumping, a prefilter system should also be utilized to remove silt and
sand prior to the carbon filter cycle. Filtering units must be sent to a chemical landfill or
incineration facility for disposal and replaced with new systems after approx. 3 to 12 months of
filtering time ( l 00 000 to l 000 000 gallons filtering).
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DISPOSAL SEQUENCE
Pump landfill water into primary holding tank . The primary holding tank must be designed to
automatically switch over to a secondary tank in parallel with the primary tank when the primary
tank is full. A schedule for testing of PCB concentration in the extracted landfill water will be
predetermined and initiated. After testing the water, it will either be released to the existing on
site sediment pond and natural water course, or treated by gravity flow or pumping into a sand
and carbon filter system and then stored in a third carbon steel holding tank for retesting or
released into the on site sediment pond and natural water course, depending on the NPDES
permit requirements. If retesting is required the water will be released or refiltered depending
on the final test results.
An alternative to utilizing a third storage tank would be to filter a small volume of the
contaminated water which may be easily contained for sampling and retesting purposes. For
details see the disposal sequence flow chart in the appendix.