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Image 1. Illicit discharge at sample location 2.

Image 2. Illicit discharge at sample location 4.

Chester Creek Illicit Discharge Inspection

Water quality conditions were surveyed by sampling thirteen locations along Chester Creek on July 25, 2001. Four illicit discharges to Chester Creek were identified and sampled during the survey. The locations of the discharge sites are indicated the map below at sample locations 2, 4, 8, and 18.

The first discharge (water quality sample location #2) is from an 8 inch PVC pipe that outlets into the storm sewer under I-35. The discharge is shown in the Image 1 (right).

The discharge was measured at 2.5 gallons/minute. The discharge may be associated with the drainage system for the freeway and/or Lief Erickson Park. Both photos reveal substantial periphyton (attached algae) growth on the concrete. Water quality data for the discharge also provides some indication of elevated potential contaminants. Specific conductivity and chloride concentrations (3,288 microSiemens/cm and 3,133+ mg/L) . Conductivity is reflection of the amount of dissolved solids in the aqueous solution.

The device used for this field test indicates the relative concentration of dissolved solids rather that the actual concentration; in this case the value indicates very high dissolved solids and could be indicating an illicit discharge. However, there did appear to be some interference with nitrate nitrogen in the water samples that may have been affecting the chloride probe, therefore the concentrations listed here should be used for comparative purposes only.

The qualitative appearance of the biological growth and the conductivity value indicates fairly conclusively that this is an illicit discharge to Chester Creek that needs further investigation and correction.

The second discharge (water quality sample location #4) is upstream of East 4th Street approximately even with East 5th Street. This discharge shown in Image 2 (above, right) is from an 18 inch CMP pipe at a measured flow of 10.5 gallons per minute or approximately 15,000 gallons per day. There are two pipes in this location with only one discharging.

The discharge water quality is some 20 degrees colder than the Creek along with a 2 mg/L higher dissolved oxygen concentration. None of the water quality characteristics of the discharge appeared to be deleterious to the Creek. In fact, the colder water temperature improves the Creek's ambient temperature.

The third discharge (water quality sample location #8) is from a 12-inch pipe on the NW corner of the East 8th Street Bridge crossing of the Creek. This was very small discharge at a measured flow 0.7 gallons/minute. The discharge has a relatively high specific conductivity at 972 microSiemens/cm that may indicate groundwater seepage into what appears to be a storm sewer or drainage system.

The final discharge (water quality sample location #18) is a storm sewer discharge entering a manhole at the Rice Lake Road crossing of the Chester Creek main branch south of Arrowhead Road. The manhole is located on the west side of Rice Lake Road. The discharge was measured at 2.5 gallons/minute. Water quality characteristics of lower temperature and relatively high specific conductivity may indicate the source to be cooling water. Similar to site 2, further investigation of this discharge is warranted.