(A) No regulated earth disturbance activities within the borough shall commence until approval by the borough of a drainage plan which demonstrates compliance with this chapter. This chapter provides standards to meet NPDES permit requirements associated with construction activities and MS4 permit requirements.
(B) (1) The water quality volume (WQv) shall be captured and treated. The WQv shall be calculated two ways. First, WQv shall be calculated using the following formula:
WQv = (c)(P)(A)
12
Where WQv = water quality volume in acre-feet |
c = Rational Method post-development runoff coefficient for the 2-year storm |
P = 1.25 inches |
A = area in acres of proposed regulated activity |
(2) Second, the WQv shall be calculated as the difference in runoff volume from pre-development to post-development for the two-year return period storm. The effect of closed depressions on the site shall be considered in this calculation. The larger of these two calculated volumes shall be used as the WQv to be captured and treated, except that in no case shall the WQv be permitted to exceed one and one-fourth inches of runoff over the site area. This standard does not limit the volume of infiltration an applicant may propose for purposes of water quantity/peak rate control.
(C) (1) The WQv shall be calculated for each post-development drainage direction on a site for sizing BMPs.
(2) Site areas having no impervious cover and no proposed disturbance during development may be excluded from the WQv calculations and do not require treatment.
(D) If an applicant is proposing to use a dry extended detention basin, wet pond, constructed wetland or other BMP that ponds water on the land surface and may receive direct sunlight, the discharge from that BMP must be treated by infiltration, a vegetated buffer, filter strip, bioretention, vegetated swale or other BMP that provides a thermal benefit to protect the high quality waters of the Bushkill Creek from thermal impacts.
(E) The WQv for a site as a result of the regulated activities must either be treated with infiltration or two acceptable BMPs such as those listed in division (O) below, except for minor areas on the periphery of the site that cannot reasonably be drained to an infiltration facility or other BMP.
(F) Infiltration BMPs shall not be constructed on fill unless the applicant demonstrates that the fill is stable and otherwise meets the infiltration BMP standards of this chapter.
(G) The applicant shall document the bedrock type(s) present on the site from published sources. Any apparent boundaries between carbonate and non-carbonate bedrock shall be verified through more detailed site evaluations by a qualified geotechnical professional.
(H) For each proposed regulated activity in the watershed where an applicant intends to use infiltration BMPs, the applicant shall conduct a preliminary site investigation, including gathering data from published sources, a field inspection of the site, a minimum of one test pit and a minimum of two percolation tests, as outlined in Appendix G. This investigation will determine depth to bedrock, depth to the seasonal high water table, soil permeability and location of special geologic features, if applicable. This investigation may be done by a certified Sewage Enforcement Officer (SEO) except that the location(s) of special geologic features shall be verified by a qualified geotechnical professional.
(I) Sites where applicants intend to use infiltration BMPs must meet the following criteria:
(1) Depth to bedrock below the invert of the BMP greater than or equal to two feet;
(2) Depth to seasonal high water table below the invert of the BMP greater than or equal to three feet; except for infiltration of residential roof runoff where the seasonal high water table must be below the invert of the BMP. (If the depth to bedrock is between two and three feet and the evidence of the seasonal high water table is not found in the soil, no further testing to locate the depth to seasonal high water table is required.);
(3) Soil permeability (as measured by the adapted 25 Pa. Code § 73.15, percolation test in Appendix G) greater than or equal to one-half inch/hour and less than or equal to 12 inches per hour;
(4) Setback distances or buffers as follows:
(a) One hundred feet from water supply wells;
(b) Fifteen feet downgradient or 100 feet upgradient from building foundations; except for residential development where the required set back is 15 feet downgradient or 40 feet upgradient from building foundations;
(c) Fifty feet from septic system drainfields; except for residential development where the required setback is 25 feet from septic system drainfields;
(d) Fifty feet from a geologic contact with carbonate bedrock unless a preliminary site investigation is done in the carbonate bedrock to show the absence of special geologic features within 50 feet of the proposed infiltration area; and
(e) One hundred feet from the property line unless documentation is provided to show that all setbacks from existing or potential future wells, foundations and drainfields on neighboring properties will be met; except for one- and two-family residential dwellings where the required setback is 40 feet unless documentation is provided to show that all setbacks from existing or potential future wells, foundations and drainfields on neighboring properties will be met.
(J) For entirely non-carbonate sites, the recharge volume (REv) shall be infiltrated unless the applicant demonstrates that it is infeasible to infiltrate the REv for reasons of seasonal high water table, permeability rate, soil depth or setback distances; or except as provided in division (I) above.
(1) The REv shall be calculated as follows:
REv = (0.25) * (I)/12 |
Where REv = Recharge volume in acre-feet |
I = impervious area in acres |
(2) The preliminary site investigation described in division (H) above is required and shall continue on different areas of the site until a potentially suitable infiltration location is found or the entire site is determined to be infeasible for infiltration. For infiltration areas that appear to be feasible based on the preliminary site investigation, the additional site investigation and testing as outlined in Appendix G shall be completed.
(3) If an applicant proposes infiltration, the borough may determine infiltration to be infeasible if there are known existing conditions or problems that may be worsened by the use of infiltration.
(4) The site must meet the conditions listed in division (I) above.
(5) If it is not feasible to infiltrate the full REv, the applicant shall infiltrate that portion of the REv that is feasible based on the site characteristics. If none of the REv can be infiltrated, REv shall be considered as part of the WQv and shall be captured and treated as described in division (I) below.
(6) If REv is infiltrated, it may be subtracted from the WQv required to be captured and treated.
(K) (1) In entirely carbonate areas, where the applicant intends to use infiltration BMPs, the preliminary site investigation described in division (H) above shall be conducted. For infiltration areas that appear feasible based on the preliminary site investigation, the applicant shall conduct the additional site investigation and testing as outlined in Appendix G. The soil depth, percolation rate and proposed loading rate, each weighted as described in § 153.041, along with the buffer from special geologic features shall be compared to the Recommendation Chart for Infiltration Stormwater Management BMPs in Carbonate Bedrock in Appendix D to determine if the site is recommended for infiltration. In addition to the recommendation from Appendix D, the conditions listed in division (I) above are required for infiltration in carbonate areas.
(2) Applicants are encouraged to infiltrate the REv, as calculated in division (J) above, but are not required to use infiltration BMPs on a carbonate site even if the site falls in the “recommended” range on the chart in Appendix D. Any amount of volume infiltrated can be subtracted from the WQv to be treated by non-infiltration BMPs. If infiltration is not proposed, the full WQv shall be treated by two acceptable BMPs, as specified in division (O) below.
(L) If a site has both carbonate and non-carbonate areas, the applicant shall investigate the ability of the non-carbonate portion of the site to fully meet this chapter to meet the requirements for REv for the whole site through infiltration. If that proves infeasible, infiltration in the carbonate area as described in division (K) above or two other non-infiltration BMPs as described in division (O) below must be used. No infiltration structure in the non-carbonate area shall be located within 50 feet of a boundary with carbonate bedrock, except when a preliminary site investigation has been done showing the absence of special geologic features within 50 feet of the proposed infiltration area.
(M) If infiltration BMPs are proposed in carbonate areas, the post-development two-year runoff volume leaving the site shall be 80% or more of the pre-development runoff volume for the carbonate portion of the site to prevent infiltration of volumes far in excess of the pre-development infiltration volume.
(N) Site areas proposed for infiltration shall be protected from disturbance and compaction except as necessary for construction of infiltration BMPs.
(O) If infiltration of the entire WQv is not proposed, the remainder of the WQv shall be treated by two acceptable BMPs in series for each discharge location. Sheet flow draining across a pervious area can be considered as one BMP. Sheet flow across impervious areas and concentrated flow shall flow through two BMPs. If sheet flow from an impervious area is to be drained across a pervious area as one BMP, the length of the pervious area must be equal to or greater than the length of impervious area. In no case may the same BMP be employed consecutively to meet the requirement of this section. Acceptable BMPs are listed below along with the recommended reference for design.
Number | Design Reference Title |
Number | Design Reference Title |
10 | Maryland Stormwater Design Manual, Maryland Department of the Environment. Baltimore, Maryland, 2000 |
11 | Pennsylvania Handbook of Best Management Practices for Developing Areas, Pennsylvania Department of Environmental Protection, 1998 |
12 | Recommended Procedures for Act 167 Drainage Plan Design, LVPC, Revised 1997 |
13 | Roof Gardens History, Design and Construction, Osmundson, Theodore. New York: W.W. Norton & Company, 1999 |
14 | The Texas Manual on Rainwater Harvesting, Texas Water Development Board, Austin, Texas. Third Edition, 2005 |
15 | VDOT Manual of Practice for Stormwater Management, Virginia Transportation Research Council, Charlottesville, Virginia, 2004 |
16 | Virginia Stormwater Management Handbook, Virginia Department of Conservation and Recreation, Richmond, Virginia, 1999 |
17 | Water Resources Engineering, Mays, L. W., John Wiley & Sons. Inc., 2005 |
18 | Urban Hydrology for Small Watersheds, Technical Report 55, US Department of Agriculture, Natural Resources Conservation Service, 1986 |
19 | US EPA, Region 1 New England web site (as of August 2005) http://www.epa.gov/NE/assistance/ceitts/stormwaterkechs/html. |
(P) (1) Stormwater runoff from hot spot land uses shall be pre-treated. In no case, may the same BMP be employed consecutively to meet this requirement and the requirement in division (O) above. Acceptable methods of pre-treatment are listed below:
Hot Spot Land Use | Pre-treatment Method(s) |
Hot Spot Land Use | Pre-treatment Method(s) |
Certain industrial uses (listed under NPDES)* | - BMPs that are a part of a stormwater pollution prevention plan under an NPDES permit |
Commercial nursery operations | - Vegetated swales/filter strip - Constructed wetlands - Stormwater collection and reuse |
Facilities that store or generate regulated substances* | - BMPs that are a part of a stormwater pollution prevention plan under an NPDES permit |
Fleet storage yards and vehicle cleaning facilities* | - BMPs that are a part of a stormwater pollution prevention plan under an NPDES permit |
Marinas* | - BMPs that are a part of a stormwater pollution prevention plan under an NPDES permit |
Outdoor storage of liquids | - Spill prevention and response program |
Salvage yards and recycling facilities | - BMPs that are a part of a stormwater pollution prevention plan under an NPDES permit |
Storage areas for public works | - Water quality inlets - Use of drip pans and/or dry sweep material under vehicles/equipment - Use of absorbent devices to reduce liquid releases - Spill prevention and response program - Diversion of stormwater away from potential contamination areas |
Vehicle fueling stations | - Water quality inlets - Spill prevention and response program |
Vehicle maintenance and repair facilities including auto parts stores | - Water quality inlets - Use of drip pans and/or dry sweep material under vehicles/equipment - Use of absorbent devices to reduce liquid releases - Spill prevention and response program |
*Regulated under the NPDES stormwater program | |
(2) Design references for the pre-treatment methods, as necessary, are listed below. If the applicant can demonstrate to the satisfaction of the borough that the proposed land use is not a hot spot, then the pre-treatment requirement would not apply.
Pre-treatment Method | Design Reference* |
Pre-treatment Method | Design Reference* |
Constructed wetlands | 4, 5, 8, 10, 16 |
Diversion of stormwater away from potential contamination areas | 4, 11 |
Stormwater collection and reuse (especially for irrigation) | 4, 14 |
Stormwater filters (sand, peat, compost and the like) | 4, 5, 10, 16 |
Vegetated swales | 2, 3, 5, 11, 16, 17 |
Water quality inlets | 4, 7, 15, 16, 19 |
*These numbers refer to the design reference title chart in division (O) above | |
(Q) The use of infiltration BMPs is prohibited on hot spot land use areas.
(R) Stormwater infiltration BMPs shall not be placed in or on a special geologic feature(s). Additionally, stormwater runoff shall not be discharged into existing on-site sinkholes.
(S) Applicants shall request, in writing, public water suppliers to provide the Zone I wellhead protection radius, as calculated by the method outlined in the Pennsylvania Department of Environmental Protection wellhead protection regulations, for any public water supply well within 400 feet of the site. In addition to the setback distances specified in division (I) above, infiltration is prohibited in the Zone I radius as defined and substantiated by the public water supplier in writing. If the applicant does not receive a response from the public water supplier, the Zone I radius is assumed to be 100 feet.
(T) The volume and rate of the net increase in stormwater runoff from the regulated activities must be managed to prevent the physical degradation of receiving waters from such effects as scour and streambank destabilization, to satisfy state water quality requirements, by controlling the two-year post-development runoff to a 30% release rate.
(U) The borough may, after consultation with DEP, approve alternative methods for meeting the state water quality requirements other than those in this section provided that they meet the minimum requirements of and do not conflict with state law including, but not limited to, the Clean Streams Law, 35 P.S. §§ 691.1 to 691.1001.
(Ord. 226-2007, passed 5-7-2007)