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
high water table season of the year. It does little good to measure a water table at 10 feet in the dry
season of the year and then have the water table rise during the spring to where it is within 1 to 2 feet
of the base of the leach field.
Improper Usage and Maintenance. Septic tank leach field systems will fail if they are improp-
erly used or maintained. Depending upon the use of the leach field, the septic tank needs to be
pumped out at regular intervals. If the septic tank becomes overloaded, solids will be forced out of
the tank into the leach field. Suspended material in the waste will then clog the soil pores and cause
effluent to rise to the surface of the leach field. Overloading can be caused by an inadequately sized
septic tank or supplying more waste to the tank than it was designed for. Many types of household
chemicals may also destroy the bacteria in the septic tank and prevent the proper functioning of the
system. Also, as part of the normal operation, septic tanks, even when functioning properly, will
accumulate sludge. This sludge needs to be pumped out on a periodic basis or it will fill the tank
and flow into the leach field causing damage. Regrettably, most septic tank users do not realize that
they have a problem until the septic effluent backs up into their home, comes to the surface of the
ground or is detected in their water well (Hofstra and Hall 1975, and Hall et al. 1980).
5.3 Regulatory Aspects
Discharge of pollutants to groundwater is regulated by the Colorado Water Quality Control Com-
mission (CWQCC) under Basic Standards for Groundwater, 3.11, 5 CCR 1002-8. In the case of
septic systems, the primary mechanism for administering these regulations is through wastewater
discharge permits for individual systems discharging greater than 2,000 gallons per day (gpd). For
those septic systems that discharge less than 2,000 gpd, counties are responsible for issuing permits.
The CWQCC assumes that, if the septic system meets either the county’s regulations or state ISDS
guidelines which are even more stringent, then adverse impacts to groundwater are not likely to oc-
cur. Thus, the primary regulations pertinent to the Marble study area are the “Gunnison County In-
dividual Sewage Disposal System Regulations” which were adopted on June 20, 1995.
951-110.000 Wright Water Engineers, Inc. Page 43