1.0 Introduction

Remedial activities were completed at the Neal's Landfill site in October 1999. Interim groundwater monitoring was initiated before the remediation and has continued on a quarterly basis to the present per the requirements of the Statement of Work (SOW) (Reference 1).

The results from the interim monitoring program along with all previous hydrologic and groundwater data were comprehensively analyzed. This analysis is reported in the Long-term Groundwater Monitoring Plan (LTMP) for Neal's Landfill (Reference 5). The analysis indicates that various hydrogeologic conditions may have changed from pre-remedial conditions. Peak storm flow rates have apparently been attenuated and PCB levels in Groundwater appeared to have risen during the remedy and immediately thereafter and now appear to have decreased to values lower than or typical of pre-remedy levels.

Viacom has volunteered to undertake an investigation, in addition to those proposed in the Long-term Groundwater Monitoring Plan, to increase understanding of the present Neal's Landfill site hydrogeology and to detect further changes from the pre- remedial conditions.

This document describes the plan for that investigation.

1.1 Long-term Groundwater Monitoring Plan

• Sampling of the Northwest Spring System will continue to evaluate trends in PCB levels under normal and storm flow conditions. Monthly low flow monitoring and storm monitoring (a total of five through mid-2004) will be done.
• Groundwater elevations under the consolidated waste will be continuously monitored to determine the effectiveness of the cap system to prevent wetting of the consolidated waste. The five shallow piezometers and one phreatic well (5A) will be monitored.
• The phreatic well levels will be monitored periodically by hand to determine if Groundwater flow patterns change.
• Fish and sediment sampling of Conard's Branch and Richland, Creek will be done to determine how PCB content is changing. Viacom proposed a single sampling of the fish and sediments late in the review period.
• Sampling of the Southwest Spring system will be done on a semi-annual sampling schedule. The LTMP contains the data and analysis that is the basis for the additional studies detailed below.

2.0 Investigation Plan Objectives

The specific individual objectives of this investigation are to:

1. Evaluate the causes of the apparent drop in peak storm flows at the Northwest Spring System and determine if there are other cost effective manners to further reduce storm flows.
2. Monitor additional storm flows and PCBs at the Northwest Spring System at higher frequencies than specified in the LTMP to build a more robust database to determine the impact of the remedy on storm flow PCB transport.
3. Determine if lateral flow of perched water under the landfill significantly wets the capped consolidated waste. If so, determine the sources and flow paths.

3.0 Investigation Plan Details

3.1 Investigation of Peak Storm Flows

The final cap and surface water control remedy was designed to route some water from swallets to surface streams and reduce storm flows. It was expected that as much as 100 acres of drainage would be diverted from the swallets of the old Cattail Pond area to the Southwest Seep Branch and that this would reduce storm flows. However, the magnitude of the reduction in storm flows is larger than expected.

To evaluate the causes of the apparent flow drop at the Northwest Spring System the following steps will be conducted.

• Previous basin studies will be identified. The estimates of the basin size from the previous studies will be assimilated and reviewed.
• Changes over time in the drainage basin will be identified and their impact on storm flows estimated.
• Viacom will also be monitoring flow and rain on an hourly basis throughout the initial five year monitoring period covered in the LTMP. Annually, the regressions for flow and rain will be updated. Storms monitored during the next year will be compared with storm events that were monitored during 1983-1985 and 1993-1994 to identify storm events from those periods that re comparable to present day storm events.
• EPA will supply Viacom with post remedy USGS storm flow data for certain agreed to periods of time that are of interest from June 2000 through November 2001. This data will be combined with Viacom's spring treatment facility flow data to determine post remedy NW spring system (Conard's Branch) peak and receding limb storm flow data that can be compared to the pre-remedy storm flow data from 1983-1985 and 1993- 1994.

As part of this evaluation, aerial photos from the early 1990s will be compared with aerial photos from the late 1990s and post remedy photos. Available 2000 aerial photos will be used from the Monroe County website. Viacom will also complete an over-flight taking new aerial photos of the area during the spring of 2002. Large changes in land use and drainage will be noted. This aerial photo analysis will be completed by the middle of 2002.

Landowners, other persons knowledgeable about drainage issues and changes in the area and storm water operators will be consulted. Field surveys of potential impact areas will be performed to identify specific features that have changed.

Discussions will be held with the following parties:

• Monroe County Drainage Board members
• Field Stone Reservoir operators
• Rogers Quarry operations personnel

There has been substantial enlargement in the nearby Rogers Quarry operations. Quarry dewatering activities could impact flows at the site. Historical information related to the operations, geology and hydrogeology of the area will be obtained and analyzed. Additional investigations, if necessary, will be undertaken.

Initial investigations of the drainage basin indicate that a large retention basin (Field Stone Reservoir) was installed in the Cave Creek watershed. A walk of the Cave Creek Stream area was done in April 2001 with the government parties. No obvious swallow holes were identified except at the terminus of the stream where the water was known to sink.

There are three indications that this reservoir is not responsible for the reductions in peak flows. First, this reservoir was not placed into operation until the fall of 1998. Yet analysis of the April 1998 event showed a drop in peak flow had already occurred. Second, there was one dye trace conducted from the Cave Creek swallets during a storm that did not show these waters resurging at Neal's Landfill. However, there is some question about this trace since the dye was injected on the receding limb of the storm. Third, Viacom's storm flow analysis shows peak flow attenuation for all storm flows. The reservoir only closes during major rain events.

Because of the size of the Cave Creek system, additional investigations will be conducted. These will entail the following:

• Establish contact with the Smith Neubecker field engineer responsible for operation of Fieldstone Dam (FSD) and be put on the call list.
• Establish contact with landowner at Cave Creek terminal swallets and secure access.
• Obtain elevations of major stage milestones at Cave Creek.
  • Low flow swallet elevations
  • Consecutive overflow swallet elevations
  • Floats 1, 2, and 3 of telemetric dam switches
• Install a stage recorder at Cave Creek.
• Monitor storm event(s).
• Evaluate data.

recorded and correlated with flows at Conard's Branch and operation of the Field Stone Reservoir. A review of this information will be conducted as a prelude to making a decision concerning a new dye trace of the Cave Creek swallets.

If a dye trace is done at the Cave Creek swallets, the tracer would be injected on the rising limb of a significant storm event. Monitoring will be done at a minimum at the Northwest Spring system on a frequent basis and possibly at other likely resurgences on a less frequent basis.

In addition to a potential dye test of the Cave Creek swallets, other sinkholes/swallets in the area may be dye injected to further delineate the basin. Decisions on additional basin delineation dye testing will be made after reviewing the new air photos, gathering initial data at Cave Creek, gathering additional data concerning the Rogers Quarry operations and field reconnaissance. It is anticipated that these decisions will be made in the summer or fall of 2002.

As part of this work any other subbasin areas that may be a significant contributor to the spring system storm flows will be identified. The impact of any identified subbasin areas on further reducing storm flows will be estimated based on drainage area. If there are significant areas identified, an initial feasibility estimate to divert additional Groundwater from the Northwest Spring System may be made based on conceptual level cost and property issues.

3.2 Storm Event Monitoring in Conard's Branch

3.3 Investigation of Lateral Flow under the RCRA Cap

To determine if lateral inflow would be significant after the final cap was placed, five piezometers were installed within the waste consolidation area under the RCRA subtitle C cap after the 1999 remedial action. These piezometers were located in areas that were found to contain saturated waste and/or low spots that may be more susceptible to backflooding. Figure 1 shows the location of the piezometers and contains a table showing the elevations of the surface and bottoms of the wells. As part of the LTMP these piezometers will be monitored to determine if Groundwater is reaching the consolidated waste.

After the piezometers were installed, only PZ-01 collected an appreciable amount of water, up to almost five feet. PZ-01 was placed near the locations of the old PZs 60 and 61. PZ-03 was reported to have two to three inches of water in the bottom. This water level is currently being observed and evaluated for its significance. The other piezometers were dry. Consequently, investigation centered on PZ-01 to determine whether this water had previously infiltrated and was trapped, or if there was active Groundwater flowing through this location.

Table 1 summarizes the history of PZ-01 measurements and observations. In late November of 1999, 4.92 feet of water was measured in the piezometer. Datalogging equipment was installed and in early March 2000 was operating. The logger ran from March 7 to October 26, 2000, but water levels were not hand checked during this period. Figure 2 shows the logger data for this period. On October 26, 2000, the logger was stopped and the hole was observed to be dry by use of a hand water level probe. The data logger never indicated a dry hole. The data logger was pulled and mud was found to be coating the instrument. This may have clogged the sensor preventing accurate measurements or the faulty indication may have been caused by a calibration problem.

It was decided to place an insert in the piezometer so a new In-situ Mini-Troll continuous water level monitor could be installed and the calibration maintained within a sump. On February 20, 2001, measurements were taken for the sump and at 15:35 hours the piezometer was dry. When personnel returned the next day, 3.28 feet of water was discovered in the piezometer and no rain had occurred for a week. Viacom has no explanation for the discrepancy of the piezometer being dry one day and having water the next with no intervening precipitation.

The Mini-Troll was installed in PZ-01 and began logging at 11:00 hours on February 2, 2001 Figure 3 shows the level data from February 21, 2001, to July 3, 2001, along with the cumulative rain plot. Based on the PZ-01 response as shown on Figure 3, Viacom does not believe there is lateral infiltration at levels of concern under the landfill. The piezometer level declined from February to early May, as would be expected since only about four inches of rain fell during that period. However, from early May through the heavy storms of early June an additional eight inches of rain fell and yet PZ-01 levels still continued their decline. If laterally infiltrating epikarstic water were feeding the PZ-01 area, a closer correlation to rainfall and level would be expected. Note that prior to the remedy the old PZ-60 and PZ-61, which were both near the location of the present PZ-01, both showed level increases after storm events. Evidently the new cap has been effective in eliminating this response.

Crest gage indicators were installed in the other four piezometers on April 12, 2001 and checked on June 14, 2001. PZ-03 had a depth to bottom of 18.79 feet and a depth to water of 18.52 feet. There was a movement of 0.75 inch on the PZ-03 crest gage, while the crest gauges in the other three piezometers showed no movement. Viacom will continue to record the level in PZ-01 through one complete hydrologic cycle (through the end of spring 2003). The other piezometers will also have their crest gauges checked during this time. If any piezometer is observed to show a significant upward response during this time period, then the potential impact of lateral infiltration must be evaluated. Manual measurements of water level in the piezometer will be made twice a month, when the datalogger data is downloaded, to verify the calibration of the piezometer.

The evaluation of the impact of any indicated lateral infiltration will be conducted by observing for any subsidence near the responding piezometer or any unexplained increase in PCB levels at the Northwest Spring System. If there is a small increase in the water level of a piezometer but no noticeable subsidence or unexplained increases in PCB levels in the spring discharges, then no further investigation of the potential lateral inflow may be warranted.

If lateral inflow is occurring as evidenced by an increase in a piezometer water level and this increase is large and/or appears to be causing either subsidence or an increase in PCB discharges to the springs, then Viacom will formulate and submit a plan to investigate the source, extent and rate of the inflow. Some of the following actions will be considered as means to determine the source and flow path of the influent water:

• Evaluate aerial photos and perform field reconnaissance for fracture trace locations.
• Perform shallow geophysics with electrical resistivity in areas of likely lateral flow.
• Drill shallow piezometers to identify flow paths and water levels.
• Review data and determine if fresh water can be re-routed.

The parties will be consulted on the evaluation of lateral inflow and/or any investigation planning.

Well EPA-5A will also be continuously monitored for water level as part of the LTMP. This well has been shown to closely match the response of the Overflow Springs at the site. This indicates it may be an accurate indication of the water potential of the main conduit under the site. Its level will also indicate any potential for backflooding. In the four inch storm of October 4, 2000, EPA-5A reached a peak elevation of 760.62 feet, which is still well below the drilling refusal (assumed bedrock) elevation of 769.95 feet at PZ-01. This indicates that no Groundwater backflooding to above the top of rock where the waste is consolidated has occurred under the cap.

4.0 Reporting

References

1. Statement of Work (SOW) for the Source Control Remedial Design and Remedial Action at Neal's Landfill, Monroe County, Indiana, March 5, 1999

2. Consent Decree, Civil Action No. IP 83-9-C, USA and the State of Indiana v. Westinghouse Electric Corporation and Monsanto Company, and Civil Action No. IP 81-448-C, The City of Bloomington and Monroe County, Indiana v. Westinghouse Electric Corporation and Monsanto Co., entered August 1985

3. Remedial Design / Remedial Action Work Plan, Neal's Landfill, Monroe County, Indiana, CBS Corp., April 23, 1999

4. Final Report- Remediation of Neal's Landfill, Bloomington, Indiana, CBS Corp, December 2000

5. Long-term Groundwater Monitoring Plan for Neal's Landfill, QAPjP Volume XXXI, Bloomington Project, Viacom Inc., April 2002