Gelman Sciences Dioxane Project;
Ann Arbor, MI

Evergreen System

HISTORY
Initial discovery of contamination in the evergreen system was in 1989. It was originally specified by the consent judgment that the discharge of treated groundwater could be accomplished by reinjection, discharge to the city of Ann Arbor sanitary sewer, or surface water discharge to the Allen drain. Implementation of the proposed work began following the approval of the work plan by the RRD in June 1993. Contaminated groundwater was extracted at the leading edge of the contamination plume, on Evergreen Street. The contaminated water was piped to a treatment system and discharged into the Ann Arbor sanitary sewer. In December 1993 GSI began injecting water treated to non-dectable limits (less than 1 ppb) into the clean Unit E Aquifer. Discharge to the Ann Arbor sanitary sewer ceased at this time. Problems with the reinjection began as soon as 1994. The reinjection well became plugged with bacteria and minerals. Frequent shutdowns of the extraction well took place and in November of 1996 monitoring determined that the plume had escaped the capture zone. At this time the sanitary sewer was again permitted to be used as a discharge area so that continuous extraction, treatment and discharge could occur.

An additional extraction well and reinjection well were installed to capture the escaped contamination on Allison Street. It appears at this time that the extraction wells are preventing further migration to the east. Groundwater extracted from the area is piped back to the PLS Site where it is treated and released to the Honey Creek Tributary.

LOCATION
The Core Area is defined as the area of the Unit C3 aquifer that is contaminated with 1,4-dioxane exceeding 500 ppb. A portion of the PLS property is situated above the Core Area. The Unit C3 Aquifer is connected to the deeper channelized D2 aquifer which flows northeast to the Evergreen System. The Core Area is also the source of contamination in the Unit E aquifer.

CURRENT STATUS
There are three extraction wells in the Evergreen subdivision and four upgradient extraction wells closer to the source of higher contamination. These wells remove 540 gallons per minute of contaminated groundwater. These wells will continue to operate until the generic residential cleanup criteria is achieved. Continued monitoring will occur at the site for ten years following the achievement of the remediation criterion.

Unit C3 (Core Area)
Unit D0 (Western System)
Unit D2 (Evergreen System)
Unit E Aquifer