A Minnesota County retained Braun Intertec to provide environmental services for the expansion of a county highway corridor in an urban area.

We began by completing a Phase I environmental site assessment (ESA) over the mile-long corridor (site). The Phase I ESA identified several car dealerships, numerous current and former gas stations (including one with an active soil and groundwater remediation system), a small engine repair shop and a dry cleaner with a known tetrachloroethene (PCE) release.

Challenges

The County intended to acquire, in their entirety, the dry cleaner property, the gas station with the remediation system and a property previously occupied by a gas station. Several other properties with known or suspected former underground storage tanks (USTs) were to be partially acquired. At other locations along the corridor, excavation was to take place in areas identified as having the potential for contamination.

Solutions

The site was entered into the VIC* and VPIC** Programs in order to obtain appropriate liability assurances for the Phase II investigation, property acquisition and construction work. We prepared the Phase II ESA work plan and a Site Health and Safety Plan in accordance with OSHA regulations.

Following Minnesota Pollution Control Agency (MPCA) approval of the work plan, the Phase II ESA was carried out on nine properties within the corridor. It consisted of sampling and analyzing soil and groundwater from 19 direct push probes. Soil samples were analyzed for some or all of the following:

• Gasoline range organics (GRO)
• Diesel range organics (DRO)
• Benzene ethyl toluene, xylenes (BETX)
• Methyl-tert-Butyl ether (MTBE)
• Volatile organic compounds (VOC)
• Polyaromatic hydrocarbons (PAH)
• Resource Conservation and Recovery Act (RCRA) metals

Groundwater samples were analyzed for DRO, GRO, VOCs, RCRA metals and SVOCs, including PAHs. Pre-demolition surveys were performed on four buildings to evaluate them for the presence of asbestos, lead paint, mercury and PCB-containing building fixtures and other potentially hazardous building materials. In addition, the contents of an unused UST located on the dry-cleaner property was sampled and analyzed for VOCs.

The Phase II ESA results were used to prepare a Construction Contingency Plan for the expansion corridor to guide the evaluation and management of potentially contaminated soil. At the request of the VIC Program, a Demolition Response Action Plan was prepared for the dry cleaner property. Demolition of the dry-cleaner building and removal of two USTs on the property will be coordinated with the MPCA, who will be carrying out additional characterization and cleanup of the PCE contamination.

An environmental technician from our team will be present during demolition of the dry-cleaning facility. The technician will assist in segregating and properly handling contaminated building materials and soils disturbed during the demolition and UST removal. We will also provide UST removal sampling and observation at an adjacent gas station property.

When road construction began in 2001, an environmental technician was present to screen soils in accordance with the contingency plan during excavation for road construction in the areas determined by the Phase II ESA to have contamination. We were on standby in the event that contamination was encountered at other locations in the corridor.

* Voluntary Investigation and Cleanup Program (VICP) ** Voluntary Petroleum Investigation and Cleanup Program (VPICP)