A. The applicant shall comply with the following water quality requirements of this section.
B. No regulated earth disturbance activities within the municipality shall commence until approval by the municipality of a plan which demonstrates compliance with state water quality requirements postconstruction is complete.
(1) The BMPs shall be designed, implemented and maintained to meet state water quality requirements, and any other more stringent requirements as determined by the municipality.
(2) To control postconstruction stormwater impacts from regulated earth disturbance activities, state water quality requirements can be met by BMPs, including site design, which provide for replication of preconstruction stormwater infiltration and runoff conditions, so that postconstruction stormwater discharges do not degrade the physical, chemical or biological characteristics of the receiving waters. As described in the DEP Comprehensive Stormwater Management Policy (#392-0300-002, September 28, 2002), this may be achieved by the following:
(a) Infiltration: replication of preconstruction stormwater infiltration conditions.
(b) Treatment: use of water quality treatment BMPs to ensure filtering out of the chemical and physical pollutants from the stormwater runoff.
(c) Stream bank and streambed protection: management of volume and rate of postconstruction stormwater discharges to prevent physical degradation of receiving waters (e.g., from scouring).
(3) Developed areas shall provide adequate storage and treatment facilities necessary to capture and treat stormwater runoff. The infiltration volume computed under § 505-125 may be a component of the water quality volume if the applicant chooses to manage both components in a single facility. If the infiltration volume is less than the water quality volume, the remaining water quality volume may be captured and treated by methods other than infiltration BMPs. The required water quality volume (WQv) is the storage capacity needed to capture and treat a portion of stormwater runoff from the developed areas of the site. To achieve this goal, the following criterion is established:
(a) The following calculation formula is to be used to determine the water quality storage volume, (WQv), in acre-feet of storage for the watershed:
WQv = [(P)(Rv)(A)]/12 Eqn: 505-126.1
WQv = Water quality volume (acre-feet)
P = 1 inch
A = Total contributing drainage area to the water quality BMP (acres)
Rv = 0.05 + 0.009(I), where I is the percent of the area that is impervious surface [(impervious area/A)*100]
(b) This volume requirement can be accomplished by the permanent volume of a wet basin or the detained volume from other BMPs.
(c) Release of water can begin at the start of the storm (i.e., the invert of the water quality orifice is at the invert of the facility). The design of the facility shall provide for protection from clogging and unwanted sedimentation.
(4) For areas within defined special protection subwatersheds which include exceptional value (EV) and high-quality (HQ) waters, the temperature and quality of water and streams shall be maintained through the use of temperature-sensitive BMPs and stormwater conveyance systems.
(5) To accomplish the above, the applicant shall submit original and innovative designs to the Municipal Engineer for review and approval. Such designs may achieve the water quality objectives through a combination of BMPs (best management practices).
(6) If a perennial or intermittent stream passes through the site, the applicant shall create a stream buffer extending a minimum of 50 feet to either side of the top-of-bank of the channel. The buffer area shall be maintained with and encouraged to use appropriate native vegetation (refer to Appendix H of Pennsylvania Handbook of Best Management Practices for Developing Area for plant lists). If the applicable rear or side yard setback is less than 50 feet, the buffer width may be reduced to 25% of the setback, to a minimum of 10 feet. If an existing buffer is legally prescribed (i.e., deed, covenant, easement, etc.) and it exceeds the requirements of this Part, the existing buffer shall be maintained. (The municipality may select a smaller or larger buffer width if desired, but the selected buffer may not be less than 10 feet). This does not include lakes or wetlands.
(7) Evidence of any necessary permit(s) for regulated earth disturbance activities from the appropriate DEP regional office must be provided to the municipality. The issuance of an NPDES construction permit [or permit coverage under the statewide general permit (PAG-2) satisfies the requirements of Subsection B(1)].