School Bus Garage

Lapeer County, Michigan

                                                                                                                                                                      

This project involved several releases of petroleum products from historical underground storage tanks (USTs) at a bus garage in Lapeer County, Michigan. Several other consultants had worked on this project for the school district over the course of years. Numerous soil borings had been completed and over 40 groundwater monitoring wells had been installed. Soil and groundwater contamination were widespread and free product was present. In addition, a large scale groundwater remediation system had been installed, however it was only operated for a short period of time with no measureable effect.

 

The district was in a very unfortunate position as they had expended over $250,000 with no apparent progress and the Michigan Department of Environmental Quality was beginning to send violation notices because the district had not lived up to their obligations under the Leaking Underground Storage Tank (LUST) rules.

 

Mr. Foerg performed an extensive file review and proposed a limited subsurface investigation to confirm existing conditions, locate and evaluate the condition of existing groundwater monitoring wells, locate residual remediation system components and confirm groundwater flow direction. This work resulted in a clear understanding of existing conditions (which had been poorly characterized by the previous consultants) and facilitated the continued use of a number of the existing groundwater monitoring wells, saving the district the cost of recreating the previous studies. In addition, a program was developed to properly remove/abandon non-useable monitoring wells and remediation system components.

 

A corrective action plan (CAP) was developed to address the releases. Extensive negotiation with MDEQ was conducted to ensure that the CAP would be approvable. Elements of the CAP included:

 

  • Periodic free product monitoring to demonstrate that free product was no longer present

  • Installing interior lining in the storm sewer that transected the areas of impact and discharged to a nearby stream. This prevented the infiltration of contaminated groundwater into the storm sewer.

  • Installation of a Sub-slab Depressurization (SSD) system to mitigate the intrusion of petroleum vapors into the music room that adjoined the bus garage. Prior to installation of the SSD system, a pilot study was conducted to confirm its effectiveness.

  • Use of the paved parking lot as an exposure barrier from impacted soils. This required a survey of the parking lot and development of an operation and maintenance plan to ensure the future integrity of the exposure barrier.

  • Periodic groundwater monitoring to demonstrate that contaminated groundwater was not migrating onto adjacent properties.  

  • Development of a restrictive covenant to prevent any structures from being built over the areas where impacts exceeded MDEQ volatilization to indoor air cleanup criteria. 

 

The CAP was approved by the MDEQ resulting in the district meeting their obligations. The costs to implement the CAP were within the districts budget.