(a) (1) The applicant shall comply with the following water quality requirements of this subchapter.
(2) A. To control post-construction stormwater impacts from regulated activities and conform to state water quality requirements, BMPs which replicate pre-development stormwater infiltration and runoff conditions must be provided in the site design such that post-construction stormwater discharges do not degrade the physical, chemical or biological characteristics of the receiving waters.
B. This may be achieved by the following:
1. Infiltration: replication of pre-construction stormwater infiltration conditions;
2. Treatment: use of water quality treatment BMPs to provide filtering of chemical and physical pollutants from the stormwater runoff; and
3. Stream bank and stream bed protection: management of volume and rate of post-construction stormwater discharges to prevent physical degradation of receiving waters (e.g., from scouring).
(3) A. Developed areas shall provide adequate storage and treatment facilities necessary to capture and treat stormwater runoff. The infiltration volume computed under § 1043.16 may be a component of the water quality volume if the applicant chooses to manage both components in a single facility. If the calculated water quality volume (WQv) is greater than the volume required to be infiltrated as described in § 1043.16(c)(2), then the difference between the two volumes shall be treated for water quality by an acceptable stormwater management practice(s). 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.
B. To achieve this requirement, the following criterion is established:
1. From Control Guideline (CG-I) in the PA BMP Manual, the water quality volume shall be the net two-year 24-hour volume. The net volume is the difference between the post-development runoff volume and the pre-development runoff volume. The post-development total runoff volume for all storms equal to or less than the two-year 24-hour duration precipitation shall not be increased. For modeling purposes, existing (pre-development) non-forested pervious areas must be considered meadow in good condition or its equivalent, and 20% of existing impervious area, when present, shall be considered meadow in good condition.
2. This volume requirement can be managed by the permanent volume of a wet basin or the detained volume from other BMPs. Where appropriate, wet basins shall be utilized for water quality control and shall follow the guidelines of the PA BMP manual referenced in Appendix H.
3. 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.
(b) The temperature of receiving waters shall be protected through the use of BMPs that moderate temperature.
(c) If a perennial or intermittent stream passes through, or a waterbody (i.e., lake, pond, wetland) is present on the site, the applicant shall create a riparian buffer extending a minimum of 50 feet, subject to federal and state buffer policies and regulation, to either side of the top-of-bank of the channel, lake or wetland. The buffer area shall be planted with native vegetation and maintained in a vegetated state (Refer to Appendix B, Pennsylvania Native Plant List, contained in the PA BMP Manual.)
(1) The following provisions also apply to riparian buffers on lots in existence at the time of adoption of this chapter:
A. If the applicable rear or side yard setback is less than 50 feet, the buffer width may be reduced to 25% of the setback or ten feet, whichever is greater.
B. If a stream traverses a site in a manner that significantly reduces the use of the site, the buffer may be either:
1. Reduced to 25 feet on either side, with municipal approval; or
2. Reduced to ten feet with municipal waiver.
(2) Permitted uses within the buffer include the following, subject to municipal approval and provided that they comply with all federal, state and local regulations:
A. Recreational trails; (See Appendix G Riparian Buffer Trail Guidelines.)
B. Utility rights-of-way;
C. Bridges; and
D. Other uses subject to municipal approval.
(3) If an existing buffer is legally prescribed (i.e., deed, covenant, easement and the like) and it exceeds the requirements of this chapter, the existing buffer shall be maintained.
(Ord. 928, passed 6-18-2014)