Phase 1 Environmental Site Assessment

E. Trafficway at National Avenue (former Ash Grove Quarry)

Date of Report: May 2, 2008
Assessment Funding:
Acres: 9.44

Site Background

The subject site includes the former Ash Grove Quarry located at the northwest corner of East Trafficway and National Avenue, directly east of Hammonds Field. The site occupies approximately 9.44 acres of land currently used as a clean fill and demolition landfill to address excavation voids from the quarry.

The property was previously investigated and closed under the Missouri Brownfields / Voluntary Cleanup Program. The southwest portion of the site (“Tract 1”) is currently subject to a restrictive covenant primarily based on elevated methane levels in soil gas. The remaining portions of the site (“Tract 2”) have been closed without restrictions.

Findings

Terracon Consultants Inc. completed a Phase I Environmental Site Assessment (ESA) of the property in May 2008. The Phase I identified six (6) soil gas observation wells within the southwest portion of the former quarry (i.e. Tract 1). Reported methane levels in excess of 17 percent by volume represent a Recognized Environmental Condition (REC) in connection with the site. The Phase I report also noted potential geotechnical implications related to unclassified fill and buried debris.

Methane impacts and other Phase I findings suggest some degree of historical fill inconsistent with the intended “clean fill” use of the property. Documented environmental conditions, however, do not suggest hazardous materials or petroleum releases to the site. Methane generation is likely attributable to degradation of buried organic debris. Continued soil gas monitoring and associated risk management evaluations are ongoing.