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.
Image 1. Illicit discharge at sample location 2. |
Image 2. Illicit discharge at sample location 4. |
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.
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