327 IAC 5-10-3 Controlled discharges

Sec. 3. (a) For all new and existing municipal-type wastewater treatment plants (including POTWs, state owned facilities, and semipublic facilities) with multiple cell waste stabilization ponds operating as controlled discharges (facilities which provide treatment by use of constructed wetlands may be included with this group, so long as other requirements are met), a discharge may occur at any time, provided a minimum dilution ratio with the receiving stream of 10:1 (ten (10) parts stream water to one (1) part effluent) is maintained. Dilution ratio is to be determined by measuring actual flow of the receiving stream upstream of the treatment plant discharge and then regulating the plant's discharge flow such that the discharge rate does not exceed one-tenth (1/10) of the measured stream flow. Plants operated in this manner are subject to the alternative effluent limitations contained in 327 IAC 5-5-3(b). In addition, water quality-based limitations for ammonia or any other toxic substance may be included in the permit if ammonia or the toxic substance is or may be discharged at a level that will cause, have the reasonable potential to cause, or contribute to an excursion above any applicable narrative or numeric water quality criteria or value promulgated under 327 IAC 2-1 or 327 IAC 2-1.5. (b) Upstream flow is to be measured using a gauging station which is calibrated at least annually. If a USGS gauging station is not available, the permittee is required to install and maintain a gauging station which is calibrated by a temporary or permanent flow measuring device. (c) Treatment facilities which are designed and operated as controlled discharge plants (multicelled) and which are not either hydraulically or organically overloaded are not required to provide disinfection of their effluent due to the natural attrition of fecal-type bacteria resulting from the long retention time. (d) The construction of any new controlled discharge waste stabilization pond-type treatment plant with a discharge either directly to a lake or reservoir (either natural or manmade impoundments) or within two (2) miles upstream of such generally will not be approved. (e) It is understood, however, that there may be cases in which there is no other treatment alternative within the financial capability of the prospective discharger and a controlled discharge must be considered. In these cases an in-depth review by the office of water management will be necessary to determine which conditions are applicable and what effects the discharge will have in each individual case.