Phase II ESA
Anwatin Woods
STS Project 97511-YK
June 30, 2003EXECUTIVE SUMMARY
Filling activities at the Anwatin Woods Dump appear to have started in the 1950s and continued into the late 1960s. The dump site is located near the western boundary of the City of Minneapolis adjacent to Theodore Wirth Park and is in a residential area. Fill materials in the dump, composed primarily of concrete, bituminous asphalt and apparent demolition debris, were observed to be from 10 feet thick to over 16 feet thick. Assuming a 20 foot thick fill layer over an approximately two acre area, the total volume of fill materials is estimated to be approximately 60,000 cubic yards.
Conditions in the dump area can be characterized as a sequence of fill soil mixed with concrete and apparent demolition debris overlying glacial till. Water bearing sandy layers occur below the till profile.
The primary concerns with fill materials in the Anwatin Woods Dump are asbestos containing materials (ACMs) and unknown contaminants which could exist. Asbestos was identified in one sample of demolition material. Additional ACMs could exist in the fill materials.
No significant exceedances of Minnesota Pollution Control Agency (MPCA) Tier I Soil Reference Values (SRVs) for human contact or Tier I Soil Leaching Values (SLVs) for leaching of contaminants to groundwater were identified in samples obtained in the dump. However, due to uncontrolled filling which occurred, unknown materials of environmental concern could exist in the dump.
No significant methane impacts were identified in the monitoring wells or test pits installed at the site.
Physical hazards from exposed concrete and debris exists on the surface and eastern slope of the dump.
1.0 General Information
The MPCA requested that STS conduct a Phase I ESA of the Anwatin Woods Dump. The Phase I ESA of the Anwatin Woods Dump indicated the potential for the dump to impact surface water and groundwater. Potential was also noted for the existence of asbestos containing materials (ACM) from demolition debris and potential physical hazards from exposed concrete on the surface. STS recommended further site investigation activities of the Anwatin Woods Dump site based on historical information obtained during the Phase I ESA.
The MPCA subsequently requested that STS conduct a Phase II ESA for the Anwatin Woods Dump. STS prepared a Phase II Investigation Work Plan dated April 1, 2003 that included the proposed locations, number and types of samples to be taken and analyses to be performed. The scope of work for the Phase II Work Plan was based on the results of the Phase I ESA.
A Site Health and Safety Plan was prepared as a companion document to the Work Plan.
1.1 Purpose and Scope
The primary objective of the Phase II ESA was to obtain and report data to determine impacts and resulting potential threats to public health and the environment. The results of the Phase II ESA were to be used to prepare a Response Action Plan (RAP) for possible reconfiguration of fill materials as part of a proposed educational park. The RAP was submitted separately.
The sampling strategy used for the Phase II ESA focused on sampling of areas thought to have the greatest potential for contamination to exist. Media considered as likely exposure pathways for potential contaminants were investigated in light of the proposed future use of the property.
Included in this report are boring and test pit logs of materials encountered during the subsurface exploration, and laboratory analysis results for surface soil, fill materials, native soil below the fill material, sediment and groundwater samples. STS has also included conclusions based on the data collected for this Phase II ESA.
1.2 Involved Parties
The Friends of the Birch Pond Watershed (FBPW/Save Anwatin Woods Neighborhood Organization) is interested in restoring a portion of the Anwatin Woods Dump property to conditions similar to those that existed prior to filling activities. The restoration project would serve as part of an environmental learning center. Draft proposed plans were prepared by the Design Center for American Urban Landscape at the University of Minnesota. The FBPW/Save Anwatin Woods organization has yet to obtain ownership of the properties associated with the Anwatin Woods Dump. Fund raising activities for property purchase and construction costs were underway at the time of preparation of this report.
1.3 Site Description
The Anwatin Woods Dump is located south of Chestnut Avenue between Xerxes Avenue South and Upton Avenue South and north of the Anwatin School, see Figures 1 and 2. The eastern approximately one-half of the 4.5 acre site contains the fill materials. The project site is located in part of the NW 1/4 of Section 26, Township 29 North, Range 24 West in Hennepin County, Minnesota.
The Anwatin Woods Dump is bordered on the north and east by residential areas, on the south by schools and on the west by Theodore Wirth Park. Walking paths crisscross the dump surface. Most of the dump is wooded. The site lies at an elevation of about 860 feet above mean sea level. Originally the site contained a depression which was approximately 20 feet (estimated) lower than the existing topography. The depression contained a pond at one time.
Large slabs of exposed concrete are exposed along the east slope of the dump area. Concrete is also exposed at numerous locations on the surface.