Welcome to TASC Two previous presentations to the CAG explained that TASC is a national EPA program that provides technical assistance services to communities. The programâ€™s goal is to help people understand complex environmental issues and ensure meaningful community involvement in environmental decision-making. The TASC program provides services through a national EPA contract. Under the contract, independent contractor Skeo Solutions provides scientists, engineers and other professionals to review and explain information to communities throughout the United States and U.S. territories.
Fact Sheet #2 Contents
Fact Sheet â€“ Page 1: Background The fact sheet provides a brief summary of the site, its geology and current ground water status. For more detailed site information, EPA and MDNR websites are great resources.
Fact Sheet â€“ Page 2: Site Geology
Areas 1 & 2 Cross-Section In Areas 1 and 2, landfill debris has been placed on top of natural soils. The soil or overburden at Areas 1 and 2 is an alluvium, consisting of layers of fine-grained clay and silt over course-grained sand and gravel. Under this soil layer is limestone bedrock. The soil or alluvium thickness varies in Area 1. It is thinner in the southwest and thicker in the northwest. The soil or alluvium thickness is about the same in Area 2. [See Figures 5-3 and 5-4 and first paragraph under Groundwater Occurrence (Section 184.108.40.206) on page 78 of the Remedial Investigation Report .]
Karst This map from the East-West Gateway Council of Governments website, as well as the West Lake Landfill Site Investigation report, indicates that the area where the West Lake Landfill Superfund site is located is not known to contain significant karst topography or sinkholes.
Fact Sheet â€“ Page 3: Ground Water
Fact Sheet â€“ Page 3: Ground Water The siteâ€™s remedial investigation indicated that the ground water flow under the site is relatively slow, less than 150 feet per year. Ground water, like surface water, flows from high areas to low areas, following the path of least resistance. Water table contour maps are made from measuring the height of ground water in monitoring wells. Ground water flows perpendicular to the contour lines.
October 2013 Figure 2 This map is from the October 2013 Ground Water Monitoring Report. The water table or top of the ground water is in the limestone bedrock south of the edge of the alluvium because the soil or alluvium is thinner in this area. The water table is in the alluvium toward the north because the soil or alluvium is thicker in this area. The measured height of the water table in monitoring wells compared to sea level are shown by the numbers in parentheses on the map. The ground water flows from areas of higher water level to areas of lower water level, perpendicular to the water table contour lines.
July 2012 Figure 2 This map is from the July 2012 Ground Water Monitoring Report.
July 1996 Figure 5-8 This map is from Figure 5-8 of the siteâ€™s Remedial Investigation Report. It shows the alluvial aquifer water table from July 1996 ground water sampling. The water table height above sea level measurements on the map show the water table is relatively flat at the West Lake Landfill site.
Fact Sheet – Pages 4-6
Fact Sheet – Pages 4-6 μg/L = micrograms per liter pCi/L = picocurie per liter
2012-2013 Ground Water Results Seventy-three (73) monitoring wells were sampled in 2012, 75 wells were sampled in April and July 2013, and 84 wells were sampled in October 2013. Additional wells were added to ground water sampling events to gain a better understanding of the impact of the site on ground water.
Dissolved Radium Above MCL (2012-2013 Sampling) This map shows monitoring well ground water samples (filtered samples) with more than 5 pCi/L of dissolved radium-226 plus radium-228 in the sample. The colors/symbols indicate how many of the four ground water samples from each well had more than 5 pCi/L of dissolved radium. The samples were taken in August 2012, April 2013, July 2013 and October 2013. The highest concentrations of dissolved radium were found in PZ-101 for each ground water sampling event (12.52 pCi/L estimate in August 2012 to 24.23 pCi/L in October 2013). In reviewing recent ground water monitoring reports and data from 1996, no patterns indicating increasing or decreasing concentrations or contaminant flow in a specific direction were obvious.
VOCs Above MCL (October 2013 Sampling) This map shows some results where VOCs exceeded their applicable MCL in October 2013. High concentrations of vinyl chloride (VC) were consistently found in Well D-93. High concentrations of chlorobenzene (ClB) were consistently found in Well PZ-112-AS. High concentrations of benzene (B) were consistently found in Wells PZ-104-SS and PZ-104SD. In Well PZ-205-AS, concentrations were 5.6 μg/L, 200 μg/L and estimated at 1,300 μg/L for August 2012, April 2013 and July 2013, respectively. For Well I-73, concentrations were less than 5 μg/L, 12 μg/L and 57 μg/L for August 2012, April 2013 and July 2013, respectively. Other results for benzene are less than 100 μg/L and are not shown on the map for simplicity. The results are reported in the site’s ground water monitoring reports.
Arsenic Arsenic was detected above its MCL in about a third of the monitoring wells. Conditions in the landfill may be mobilizing (causing it to dissolve into the ground water) arsenic in landfill debris or in naturally occurring rocks and soil beneath the landfill debris. A review of the Record of Decision (ROD) for North St. Louis County sites being cleaned up under the Formerly Utilized Sites Remedial Action Program (FUSRAP) indicates that arsenic is also a contaminant of concern for shallow ground water. High concentrations in deeper ground water are attributed to ground water natural conditions. High concentrations in Coldwater Creek sediment are attributed to historical industrial activity in the area, not to site activities covered in the ROD. There does not appear to be any evidence in the ROD that material moved from the Latty Avenue Property to West Lake Landfill may have contained high concentrations of arsenic.
Arsenic in Ground Water (Background) Background levels of arsenic in ground water in the St. Louis County region were low in this United States Geological Survey (USGS) report.
TASC Contact Information