Project Highlights

ACEC/GA Engineering Excellence Award

S&ME expedited environmental corrective action services at the Georgia Department of Transportation’s (DOT) maintenance headquarters in Summerville. The project, for the Georgia Environmental Facilities Authority (GEFA), met site remediation goals required by the Georgia Environmental Protection Division’s Underground Storage Tank Management Program (EPD/USTMP).

Contamination at the site resulted from a gasoline release from an underground storage tank once located there. S&ME removed free-phase product and reduced the levels of petroleum hydrocarbon constituents (chemicals of concern, or CoC) in the site’s groundwater. Quick action was required to keep the free-phased product plume from migrating off site. A significant obstacle for S&ME, considering the significantly limited working space (about a ¼-acre crowded corner area of the site, occupied by two headquarters buildings), was to complete the remedial corrective action while protecting the structural integrity of the buildings.

S&ME was faced with finding an efficient yet cost-effective method for cleaning up the site. A typical solution to remediate a free-phase product plume would be a vapor-extraction, enhanced pump and treatment system. However, such a system here would have been costly to install and remediation would take up to five years of expensive operations. Further, the site is not eligible for reimbursement under the Georgia UST Trust Fu

A second option would have been to excavate the contaminated soils. However, our working space was confined to about a ¼-acre area dominated by DOT Maintenance Headquarters buildings that had to remain in operation. And to reach such a depth would require bringing in excavation equipment, stepping down (benching) the excavations, likely shoring up of the walls, and creating an extensive footprint that could threaten the foundations of the DOT’s structures. Thinking outside-the-box was needed. S&ME’s design avoided these issues, by using a caisson drilling rig with over sized augers to drill to the 30’ depth and extract the contaminated soils through the drill holes.

Our design called for a barrier wall of eleven 2’ diameter borings about a foot apart, positioned to create an interceptor-type trench barrier and maximize the removal of about 90 tons of contaminated soils. After removing soil from each boring, we installed recovery wells with 4-inch slotted PVC screens and risers to grade in each boring. S&ME could then monitor the groundwater conditions and use the wells to recover any contamination missed during drilling.

Specific S&ME services included preparation of a site-specific corrective action plan and engineering report for the EPD/USTMP’s approval. After negotiations with the regulatory agencies, our plan and report were accepted. S&ME then successfully executed a unique plan to “excavate” 90 tons of contaminated soils (from depths down to more than 30 feet) by an over-drilling approach. As verified by extensive monitoring, our methodology eradicated free-phased product from the site and produced a satisfactory reduction of the dissolved CoC. The project was completed in a much more cost-effective and timely manner than had S&ME used conventional dig and haul or vapor extraction pump and treat approaches.

The American Council of Engineering Companies of Georgia and the Georgia Engineering Alliance awarded S&ME the Honor Award for Engineering Excellence for this site in 2006.