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City of San Mateo Municipal Code.


(a) The Director of Public Works may approve the discharge of ground waters to the sanitary sewer only when such source is deemed unacceptable by State and Federal authorities for discharge to surface waters of the United States, whether pretreated or untreated, and for which no reasonable alternative method of disposal is available. No discharge of such waters will occur except as specifically authorized in a waste discharge permit or other written authorization.

(b) Groundwater containing petroleum products may be authorized for disposal to the sanitary sewer and shall comply with the following limits at point of discharge, in addition to any other discharge standards imposed: 0.5 mg/L benzene, 1 mg/L BTEX (benzene, toluene, ethylbenzene, xylene), and 10 mg/L TPH (total petroleum hydrocarbons) as gasoline or diesel. Groundwater containing organic compounds other than gasoline or diesel shall not exceed 1 mg/L total priority organic toxic pollutants at point of discharge.

(c) Groundwater sources may include, but are not limited to: (1) construction site dewatering where soil or groundwater contamination is present; (2) groundwater contaminated with organic solvents generated as a result of pump tests in preparation for a groundwater cleanup or water generated during sampling events; (3) aqueous wastes generated by either permanent or mobile hazardous waste treatment units used to treat hazardous waste at the generator's site; (4) and aqueous wastes generated as a result of site cleanup activities. A permit must be obtained prior to commencement of discharge, and request for such permits shall be submitted not less than 30 working days prior to intended discharge.

(d) The Director limits groundwater discharges to a cumulative total hydraulic allocation of 0.5 million gallons per day (mgd) for the protection of the hydraulic capacity of the POTW. Real properties of the City or District shall have priority to said allocation. Allocations for other permit holders may be reduced, but not eliminated, to equitably accommodate the needs of the agencies to discharge treated groundwater to the sanitary sewer. Should such a permit holder discontinue discharging for more than 90 days, the permit holder shall be notified in writing of the Director's intention to cancel the permit.

(e) The Director may impose upon the user a hydraulic loading charge for discharge of groundwater or other waters in cases where conventional sewer service charges applied by the City or District do not account for said flows or uses. User discharges which exceed 10,000 gallons per batch discharge or users undertaking long term discharges of groundwater to the sanitary sewer shall be metered and levied a hydraulic loading charge based upon the basic sewer service charge rate established by the City or District, as applicable.