Rule 3745-5-09 | Determining water quality baselines.
(A) For permittees in an area where there is an approved TMDL, the water quality baseline shall be the lower of the following:
(1) The wasteload allocation established by the approved TMDL.
(2) The current discharge level.
(B) For permittees in an area where there is not an approved TMDL or where water quality fully supports designated uses assigned in Chapter 3745-1 of the Administrative Code, the water quality baseline shall be the lower of the following:
(1) The existing NPDES permit limit.
(2) A technology-based performance standard.
(3) The current discharge level.
(C) For nonpoint sources, the water quality baseline shall be the pollutant load associated with existing land uses and management practices. Existing management practices shall comply with any applicable federal, state or local requirements and shall be established as follows:
(1) By using the following:
(a) Accurate, representative, and reliable process and operational information.
(b) Available flow and monitoring data.
(c) Pollutant loading data.
(d) Available records that are deemed acceptable by the director.
(2) Unless otherwise specified in this chapter, by using information and data representative of the three year period before the date that a change is made to generate a pollutant load reduction. A different time period, such as the previous full crop rotation history, that is representative of historical operations and provides accurate and reliable data on existing pollutant loads may be used if certified by a qualified soil and water conservation professional or deemed acceptable by the director.
(D) For storm water sources regulated under an NPDES permit, the water quality baseline shall be either of the following:
(1) The numeric effluent limit, if one is established in the NPDES permit.
(2) The pollutant-specific loading achieved after implementation of management practices specified in or approved under the NPDES permit.
(E) The director may consider data and information submitted as part of a water quality trading management plan application that supports the use of alternate methods of setting baselines, provided that the data is established as follows:
(1) By using information representative of a three year period.
(2) By using the following:
(a) Accurate, representative, and reliable process and operational information.
(b) Available flow and monitoring data.
(c) Pollutant loading data.
(d) Available records that are deemed acceptable by the director.
Supplemental Information