Geologic And Hydrologic Factors Governing ... - Gunnison County

Geologic And Hydrologic Factors Governing Impacts Of Development
On The Crystal River Near Marble, Colorado
Gunnison County, Colorado
5.4 million pounds x
7
1, 000, 000
= 37.8 pounds of N/day
3. With 1 EQR contributing 0.10 lbs of N per day, the allowable pollution load for leaching
fields inflow would be 378 EQR. In the event the creek flow was at 2 cfs, the allowable
number of EQR contributing pollutants to Carbonate Creek would be 756, twice that for a 1
cfs flow.
Taking into consideration the effluent from leaching fields, the cumulative pollutant impact
of NO3-N would impact Carbonate Creek surface flows at a relatively high level of leaching
field density in the Carbonate Creek basin. Direct discharge of effluent to Carbonate Creek
would have a numerically somewhat lower, but similar impact on the quality of Carbonate
Creek. However, with a surface discharge, the impact would also relate to questions of
harmful organisms, such as fecal coliform bacteria and viruses, during times that the sewage
treatment plant malfunctioned.
This example provides a simplified approximate procedure for computing the carrying ca-
pacity of a basin under steady-state future conditions after pollutant inflow become equal to
pollutant outflow.
5.10.4 Impact on the Shale Bedrock
Shale bedrock is characterized as having secondary permeability created by cracks and joints ex-
tending downward with varying distances, but generally no more than about 50 feet. The following
approximate procedure provides a method of estimating the pollutional impact on a bedrock aquifer.
Assuming one such crack or fissure per 10 feet on the average and each crack or joint having a rate
of flow capability of 0.5 gpm, a 209-foot-wide section of the aquifer would have a groundwater flow
capability of approximately 10 gpm, or 14,400 gpd.
951-110.000 Wright Water Engineers, Inc. Page 54