Remediation Status: Site closed

Final remediation design:
Based upon the present development of the site, its present zoning for a shopping center, and the nature of the surrounding developments, it was assumed that the property would remain commercial or non-residential in the future. Nevertheless, the concentration of the contaminants present were compared to applicable residential cleanup target values, in order to close the site without restrictions as to future use or activity.

Results to date:
The maximum levels of contamination in the groundwater were above the Tier 1 residential levels for the indoor inhalation pathway and the domestic water use pathway. For the indoor inhalation pathway, the representative concentration for PCE was calculated and determined to be below the residential levels. The groundwater was monitored for four quarters beginning in 2004. The source of the contamination was no longer present (i.e., drycleaning facility) and the groundwater plume was stable with decreasing contaminant levels and a risk assessment was subsequently conducted. The domestic water-use pathway was determined to be incomplete based on a "weight of evidence" evaluation that included the following: · The Public Water Supply District No. 1 serves the site and surrounding area. · The City of Arnold's City Code effectively limits the installation of private water supply wells by requiring water distribution systems to be connected to a public water supply if available. · There are no known public water supply wells within one mile of the site or known private water supply wells within one-quarter mile of the site. However, there may be isolated instances of continued use of private water supply wells in the Arnold urban area. · Missouri's Well Construction Code requires domestic wells in Area 1 (which encompasses all of Jefferson County) to have at least 80 ft of casing extending not less than 30 ft into un-weathered bedrock. This would prevent use of the shallow strata most likely to be impacted by the contamination from being used a source of domestic water supply. A Certification of Completion was subsequently issued.

Next Steps:
Site is closed.