The purpose of monitoring wells is to obtain representative groundwater quality samples and hydrogeologic information. They are generally located between a known or suspected source of groundwater contamination and a water supply well so contaminant plumes are detected before they reach the water supply.

Sentinel Well 29

A monitoring well was installed in 2009 to monitor any migration of contaminants from the Sycamore landfill toward Unit Well 29.

Semi-annual monitoring of both inorganic and volatile organic compounds is conducted at the sentinel well. There have been some minor detects, but most can be attributed to the coating on the well liner. Benzene has been detected in the shallow ports at levels ranging between 0.12 - 0.32 ppb (MCL = 5). Trichlorofluoromethane has also been detected in the shallow ports at levels ranging from 0.13 - 1.6 ppb (no MCL). Toluene has been detected at concentrations between 0.13 – 2.8 ppb (MCL = 1000) in all of the ports.

Sampling indicates that the migration of contaminants from the Sycamore landfill is not a significant threat to water quality at Unit Well 29 at this time.

University Crossing Monitoring Wells

A set of three shallow monitoring wells were installed at the University Crossing Development (near Unit Well 14) to observe groundwater quality during site redevelopment. The wells were installed in March of 2012 with MWU paying 50% of the installation costs. The wells will be sampled and analyzed on a quarterly basis for a period of two years. All sampling costs are paid 100% by MWU.

No Volatile Organic Compounds (VOCs) have been detected in any of the three monitoring wells. Elevated levels of several inorganic compounds exist in the wells (chloride, sodium, and nitrates). These levels, however, do not appear to be increasing as the development progresses.

Summary of test results (November 14, 2012)