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. |
