Ex-Situ Groundwater Treatment System, Dave’s Party Store

Hart, MI

 

Background

The City of Hart and their contracted engineering firm began street and utility infrastructure improvements within the Hart Street right of way (ROW) adjacent to Dave’s Party Store. The store property has been an active gas station since 1991 with underground storage tanks (USTs). The site has had two gasoline releases (2017 & 2020) into the subsurface which occurred under separate owner/operators and funded by Michigan Underground Storage Tank Authority (MUSTA) reimbursement claims.

The Challenge

The City of Hart needed to safely dewater the work area within the City of Hart ROW for Hart Street and properly treat the recovered groundwater before discharge into the city’s sanitary sewer system. The city also needed support with waste approval for the impacted soil that would be removed during the work.

ERG’s Solution

In late 2023, ERG was retained by both responsible parties to act as their Qualified UST Consultant and design necessary treatment options related to the releases.

In March 2024, ERG oversaw the installation of the dewatering system and groundwater treatment system. The following tasks were performed before and during the road and infrastructure improvements.

  • Design, installation and operation of a mobile groundwater treatment system capable of interconnecting with the city contractor’s dewatering system at a designed flow rate of 300 gallons per minute.

    • The system consisted of a 20,000-gallon frac tank, sediment prefilters, liquid granular activated carbon treatment vessels and a discharge pumping system.

  • Dewatering effluent treatment and discharge of treatment effluent to the City of Hart sanitary sewer system.

  • Discharge monitoring and sampling/

  • Impacted soil screening and tracking of any waste disposal.

  • Field screening of the dewatered soils indicated no residual impacts to the clean sands and no soils were excavated or transported off-site for disposal.

Client Results

  • 175,400 gallons of gasoline impacted groundwater treated and discharged.

  • Approximate project value: $425,000

  • Ex-situ treatment costs approximately $145,000

  • Post treatment, groundwater sampling results indicate the extent of shallow groundwater impact had been contained on site with significant reductions within the for Hart Street ROW to the northeast of the release area.

 
 

 SERVICES PROVIDED

Site Investigation

Groundwater Treatment system operation, monitoring and reporting

Dewatering effluent sampling

Soil excavation oversight