1987-12-01_PERMIT FILE - C1981017 (187)

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COLORADO DEPARTMENT OF HEALTH Water Quality Control Division Rationale - Page 2 Permit No. CO-0000396 APPLICABLE RULES AND REGULATIONS: State effluent standards (SES) apply to the gray water while federal best available technology economically achievable (BAT), SES and state water quality standards (WQS) apply to surface runoff. A comparison of all appropriate limitations is shown below. TABLE 1 Parameter BAT SES WQS pH, s.u. 6.0 - 9.0 6.0 - 9.0 6.5 - 9.0 Oil and Grease, mg/l N/A 10 N/A BOD5, mg/l N/A 30/45 N/A Total Suspended Solids, mg/l 35/70 30/45 N/A Total Iron, mg/l 3.5/7.0 N/A N/A 1/ Fecal Coliform, No/100 ml N/A 6,000/12,000 N/A Settleable Solids, ml/1 2/ 0.5 N/A N/A Salinity 3/ N/A N/A N/A 1/ Neither iron nor other metals limitations apply to the gray water discharge. WQS-based metals limitations are not appropriate for surface runoff discharges because discharge normally occurs intermittently and in response to precipitation events during periods when receiving water flows are elevated. 2/ Settleable solids limitations apply only to precipitation caused discharges where volumes are less than or equal to the 10-year, 24-hour event. 3/ In compliance with the "Regulations for Implementation of the Colorado River Salinity Standards Through the NPDES Permit Program", the permittee shall sample for salinity in the wastewater effluent on a monthly basis until six samples have been analyzed. Thereafter monitoring shall continue on a quarterly basis. The Division will review the first six months of data and determine if a waiver of numeric limitations can be granted based on the salt-load to the river being less than one ton/day (or 350 tons/ year). If a waiver is not granted, then the permittee has an additional six months to submit a report in accordance with the Salinity Regulations, addressing economic feasability of salt-removal.