Braun Intertec performed a remedial investigation, a feasibility study and remedial action work for the extension of Interstate 394 in Minneapolis.

The investigation included seven individual parcels, all of which have been contaminated with petroleum derivatives from past land uses. Parcels include present and former gasoline stations and light industrial areas.

We performed a site reconnaissance, reviewed historical documents and aerial photographs, and performed drilling and chemical analysis of soil from 44 borings on four parcels within a one-month period and 30 borings at three parcels in a two-month period.

Challenges

Sixteen monitoring wells were installed at the seven parcels. Groundwater samples were collected for analysis of benzene, ethylbenzene, toluene, xylenes, and total hydrocarbons as gasoline and fuel oil, as well as other volatile organic compounds. The results of these investigations indicated petroleum and solvent contamination.

Solutions

In order to determine the impact of temporary and permanent dewatering, our team of hydrogeologists conducted an aquifer-pumping test. Results of this test were used in a groundwater computer model to predict the radius of influence of the dewatering system on the surrounding region. They also helped to determine subsequent impact upon contaminated areas and possible settlement of soils in the vicinity of the site. Information obtained from these activities was used to design groundwater recovery systems and soil remediation strategies.

In recognition of our efforts on this project, the Minnesota Consulting Engineers Council presented us with an Engineering Excellence Grand Award in January 1990.