5.0 CONCLUSIONS

STS Consultants, Ltd. (STS) has completed a Phase II Environmental Site Assessment (ESA) for the Anwatin Woods Dump located in Minneapolis, Minnesota. Filling of the dump occurred in the 1950s through 1960s. Materials were placed in a depressional area which included a pond. Disposed materials included primarily concrete and bituminous asphalt, soil and minor amounts of apparent demolition debris. The dump is located at the south end of Vincent Avenue South approximately 1/4 mile south of its intersection with Chestnut Avenue. The dump covers approximately two acres. The site is located in the NW 1/4 of Section 26, Township 29 North, Range 24 West in Hennepin County, Minnesota. The dump is on privately and publicly owned land.

Five test pits were excavated and three monitoring wells installed for the Phase II ESA. Observations were made of the types of fill materials encountered in the test pits. Samples of fill materials, samples of native soil underlying the fill, surface soil samples, sediment samples and groundwater samples were collected for laboratory analysis.

The conclusions based on this Phase II ESA are as follows:

Conditions in the dump area consist of silty sand cover soils and exposed concrete over silty sand to medium sand mixed with primarily concrete and bituminous asphalt with minor amounts of apparent demolition debris over silty clay native soils.

Hydrogeologic conditions in the area generally consist of silty sand and fine to medium sand water bearing layers below silty clay glacial till. Water bearing layers in glacial till are typically discontinuous. As such, direction of groundwater flow may not be an accurate representation, but appeared to be to the south at the site.

Fill materials encountered in the dump area were 10 to greater than 16 feet in thickness. Fill materials included concrete, brick, soil and bituminous asphalt. Minor amounts of apparent demolition materials were also observed. The dump covers approximately two acres. The volume of fill materials was estimated to be approximately 60,000 cubic yards.

Asbestos was identified in a piece of buried demolition material in the dump fill section.

No significant methane impacts were identified in the test pits or monitoring wells completed at the site

Metals were identified in some of the surface soil samples. Arsenic was detected at a concentration slightly above its MPCA established Tier 1 Soil Leaching Value (SLV) and Soil Reference Value (SRV) in a single surface soil sample

Antimony was reported at a concentration slightly above its SLV in one surface soil sample. Iron was present above the Tier 1 Soil Reference Value (SRV) in all of the five surface soil samples taken. á Antimony and chromium were detected in individual samples of fill materials at concentrations slightly above their respective SLVs.

Iron exceeded its SRV in four of the five fill material samples taken. Copper exceeded its SRV and SLV in one sample of fill materia

Iron exceeded its SRV in the one soil sample obtained from native soils below the fill materials.

Lead and manganese concentrations exceeded their lowest effect level in sediment samples taken from low lying areas at the east end of the dump

The Minnesota Department of Health, Health Risk Limit (HRL) for manganese was exceeded in groundwater at all three monitoring wells for both sampling rounds. The HRL for antimony was exceeded at monitoring well MW-2 for one sampling round only. The EPA Maximum Contaminant Level action level for lead was exceeded at Monitoring Well MW-2 for one sampling round. No other exceedances of established drinking water standards reviewed for this Phase II ESA were exceeded. The shallow groundwater in the area is not used for drinking water.

Physical hazards associated with exposed concrete and debris exists on the surface and eastern slope of the dump.

The primary concerns associated with fill materials in the Anwatin Woods Dump appear to be ACMs of demolition materials and the possibility that unknown contaminants may exist.

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. It should be noted that iron was detected in many of the samples collected from the site. Iron concentrations were generally below 15,000 mg/kg. The MPCA has previously determined, based on discussions with Minnesota Department of Health Toxicologists, that soil with iron concentrations less than 15,000 mg/kg present on a residential development site can be handled and reused as clean fill. Consequently, this Phase II ESA assumes that elevated iron concentrations in existing media at the site do not represent an environmental concern and need not be specifically addressed. In addition, concentrations of other metals identified were not at levels of concern.