Source: http://stockertown.org/stormwater-article3.htm
Timestamp: 2018-05-23 08:48:25
Document Index: 5973866

Matched Legal Cases: ['§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 73', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 205', '§ 73', '§ 73']

Article III: Stormwater Management Requirements
§ 205-11 General requirements.
§ 205-12 Permit requirements by other government entities.
§ 205-13 Erosion and sediment control during regulated earth disturbance activities.
§ 205-14 Post-construction water quality criteria.
§ 205-15 Stormwater management districts.
§ 205-16 Stormwater management district implementation provisions.
§ 205-17 Calculation methodology.
Where a site is traversed by watercourses, other than those for which a one-hundred-year floodplain is defined by the municipality, there shall be provided drainage easements conforming substantially with the line of such watercourses. The width of any easement shall be adequate to provide for unobstructed flow of storm runoff based on calculations made in conformance with § 205-17 for the one-hundred-year return period runoff and to provide a freeboard allowance of 0.5 foot above the design water surface level. The terms of the easement shall prohibit excavation, the placing of fill or structures, and any alterations which may adversely affect the flow of stormwater within any portion of the easement. Also, periodic maintenance of the easement to ensure proper runoff conveyance shall be required. Watercourses for which the one-hundred-year floodplain is formally defined are subject to the applicable municipal floodplain regulations.
Post-construction BMPs shall be designed, installed, operated and maintained to meet the requirements of the Clean Streams Law
and implementing regulations, including the established practices in 25 Pa. Code Chapter 102 and the specifications of this chapter as to prevent accelerated erosion in watercourse channels and at all points of discharge.
Techniques described in Appendix F (Low-Impact Development)
of this chapter are encouraged because they reduce the costs of complying with the requirements of this chapter and the state water quality requirements.
Infiltration for stormwater management is encouraged where soils and geology permit, consistent with the provisions of this chapter and, where appropriate, the Recommendation Chart for Infiltration Stormwater Management BMPs in Carbonate Bedrock in Appendix D.
A = area in acres of proposed regulated activity
Second, the WQv shall be calculated as the difference in runoff volume from predevelopment 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 be WQv be permitted to exceed 1.25 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.
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.
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 § 205-14O, except for minor areas on the periphery of the site that cannot reasonably be drained to an infiltration facility or other BMP.
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.
Editor's Note: Appendix G is included at the end of this chapter.
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.
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.)
Soil permeability (as measured by the adapted 25 Pa. Code § 73.15 percolation test in Appendix G) greater than or equal to 0.5 inches/hour and less than or equal to 12 inches per hour.
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.
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.
For entirely noncarbonate 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 § 205-14U.
I = impervious area in acres
The preliminary site investigation described in § 205-14H 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
The site must meet the conditions listed in § 205-14I.
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 § 205-14O.
In entirely carbonate areas, where the applicant intends to us infiltration BMPs, the preliminary site investigation described in § 205-14H 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 § 205-17, 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 § 205-14I are required for infiltration in carbonate areas. Applicants are encouraged to infiltrate the REv, as calculated in § 205-14J, 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 noninfiltration BMPs. If infiltration is not proposed, the full WQv shall be treated by two acceptable BMPs, as specified in § 205-14O.
If a site has both carbonate and noncarbonate areas, the applicant shall investigate the ability of the noncarbonate 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 § 205-14K or two other noninfiltration BMPs as described in § 205-14O must be used. No infiltration structure in the noncarbonate 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.
BioretentionA 4, 5, 11, 16
Capture/reuseB 4, 14
Constructed wetlands 4, 5, 8, 10, 16
Dry extended detention ponds 4, 5, 8, 12,18
Minimum disturbance/Minimum maintenance practices 1, 9
Significant reduction of existing impervious cover N/A
Stormwater filtersA (sand, peat, compost, etc.) 4, 5, 10, 16
Vegetated buffers/filter strips 2, 3, 5, 11, 16, 17
Vegetated roofs 4, 13
Vegetated swalesA 2, 3, 5, 11, 16, 17
Water quality inletsD 4, 7, 15, 16, 19
Wet detention ponds 4, 5, 6, 8
A This BMP could be designed with or without an infiltration component. If infiltration is proposed, the site and BMP will be subject to the testing and other infiltration requirements in this chapter.
B If this BMP is used to treat the entire WQv, then it is the only BMP required because of this BMPs superior water quality performance.
C See table below.
D Water quality inlets include such BMPs as oil/water separators, sediment traps/catch basin sumps, and trash/debris collectors in catch basins.
1 "Conservation Design For Stormwater Management — A Design Approach to Reduce Stormwater Impacts From Land Development and Achieve Multiple Objectives Related to Land Use," Delaware Department of Natural Resources and Environmental Control, The Environmental Management Center of the Brandywine Conservancy, September 1997
2 "A Current Assessment of Urban Best Management Practices: Techniques for Reducing Nonpoint Source Pollution in the Coastal Zone," Schueler, T.R., Kumble, P. and Heraty, M., Metropolitan Washington Council of Governments, 1992.
3 "Design of Roadside Channels with Flexible Linings," Federal Highway Administration, Chen, Y. H. and Cotton, G. K., Hydraulic Engineering Circular 15, FHWA-IP-87-7, McLean Virginia, 1988.
4 "Draft Stormwater Best Management Practices Manual," Pennsylvania Department of Environmental Protection, January 2005.
5 "Evaluation and Management of Highway Runoff Water Quality," Federal Highway Administration, FHWA-PD-96-032, Washington, D.C., 1996.
6 "Evaporation Maps of the United States," U.S. Weather Bureau (now NOAA/National Weather Service) Technical Paper 37, Published by Department of Commerce, Washington D.C., 1959.
7 "Georgia Stormwater Manual," AMEC Earth and Environmental, Center for Watershed Protection, Debo and Associates, Jordan Jones and Goulding, Atlanta Regional Commission, Atlanta, Georgia, 2001.
8 "Hydraulic Design of Highway Culverts," Federal Highway Administration, FHWA HDS 5, Washington, D.C., 1985 (revised May 2005).
9 "Low Impact Development Design Strategies An Integrated Design Approach, Prince Georges County, Maryland Department of Environmental Resources, June 1999.
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 and 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 and 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/stormwater/techs/html.
Stormwater runoff from hot spot land uses shall be pretreated. In no case, may the same BMP be employed consecutively to meet this requirement and the requirement in § 205-14O.
Vehicle maintenance and repair facilities including auto parts stores Water quality inlets Use of drip plans and/or dry sweep material under vehicles/equipment Use of absorbent devices to reduce liquid releases Spill prevention and response program
Vehicle fueling stations Water quality inlets Spill prevention and response program
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
Outdoor storage of liquids Spill prevention and response program
Commercial nursery operations Vegetated swales/filter strips Constructed wetlands Stormwater collection and reuse
Salvage yards and recycling facilities* 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
Facilities that store or generate regulated substances* 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
Certain industrial uses (listed under NPDES)* BMPs that are a part of a stormwater pollution prevention plan under an NPDES permit
Diversion of stormwater away from potential contamination areas 4, 11
Stormwater collection and reuse (especially for irrigation) 4, 14
Stormwater filters (sand, peat, compost, etc.) 4, 5, 10, 16
Vegetated swales 2,3,5,11,16,17
Water quality inlets 4, 7, 15, 16, 19
A These numbers refer to the Design Reference Title Chart in § 205-14O above.
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 § 205-14I, 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.
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 thirty-percent release rate.
The municipality 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.
Mapping of stormwater management districts. To implement the provisions of the Bushkill Creek Watershed Stormwater Management Plan, the municipality is hereby divided into stormwater management districts consistent with the Bushkill Creek Release Rate Map presented in the plan update. The boundaries of the stormwater management districts are shown on an official map which is available for inspection at the municipal office. A copy of the official map at a reduced scale is included in Appendix A
Description of stormwater management districts. Two types of stormwater management districts may be applicable to the municipality, namely "conditional/provisional no detention districts" and "dual release rate districts" as described below.
Conditional/provisional no detention districts. Within these districts, the capacity of the local runoff conveyance facilities (as defined in Article II) must be calculated to determine if adequate capacity exists. For this determination, the developer must calculate peak flows assuming that the site is developed as proposed and that the remainder of the local watershed is in the existing condition. The developer must also calculate peak flows assuming that the entire local watershed is developed per current zoning and that all new development would use the runoff controls specified by this chapter. The larger of the two peak flows calculated will be used in determining if adequate capacity exists. If adequate capacity exists to safely transport runoff from the site to the main channel (as defined in Article II), these watershed areas may discharge post-development peak runoff without detention facilities. If the capacity calculations show that the local runoff conveyance facilities lack adequate capacity, the developer shall either use a one-hundred-percent release rate control or provide increased capacity of downstream elements to convey increased peak flows consistent with § 205-16P. Any capacity improvements must be designed to convey runoff from development of all areas tributary to the improvement consistent with the capacity criteria specified in § 205-16D. By definition, a storm drainage problem area associated with the local runoff conveyance facilities indicates that adequate capacity does not exist. Sites in these districts are still required to meet all of the water quality requirements in § 205-14.
Dual release rate districts. Within these districts, the two-year post-development peak discharge must be controlled to 30% of the predevelopment two-year runoff peak. Further, the ten-, twenty-five-, and one-hundred-year post-development peak runoff must be controlled to the stated percentage of the predevelopment peak. Release rates associated with the ten-year through one-hundred-year events vary from 50% to 100% depending upon location in the watershed.
Any stormwater management controls required by this chapter and subject to a dual release rate criteria shall meet the applicable release rate criteria for each of the two-, ten-, twenty-five-, and one-hundred-year return period runoff events consistent with the calculation methodology specified in § 205-17.
For a proposed development site located partially within a release rate category subarea and partially within a conditional/provisional no detention subarea, the size of the predevelopment drainage area on a site may not be changed post-development to create potentially adverse conditions on downstream properties except as part of a no harm or hardship waiver procedure.
No portion of a site may be regraded between the Bushkill Creek Watershed and any adjacent watershed except as part of a no harm or hardship waiver procedure.
Within a release rate category area, for a proposed development site which has areas which drain to a closed depression(s), the design release from the site will be the lesser of: a) the applicable release rate flow assuming no closed depression(s); or b) the existing peak flow actually leaving the site. In cases where b) would result in an unreasonably small design release, the design discharge of less than or equal to the release rate will be determined by the available downstream conveyance capacity to the main channel calculated using § 205-16D and the minimum orifice criteria.
Off-site areas which drain through a proposed development site are not subject to release rate criteria when determining allowable peak runoff rates. However, on-site drainage facilities shall be designed to safely convey off-site flows through the development site using the capacity criteria in § 205-16D and the detention criteria in § 205-17.
No harm water quantity option.
For any proposed development site not located in a conditional/provisional no detention district, the developer has the option of using a less restrictive runoff control (including no detention) if the developer can prove that special circumstances exist for the proposed development site and that no harm would be caused by discharging at a higher runoff rate than that specified by the plan. Special circumstances are defined as any hydrologic or hydraulic aspects of the development itself not specifically considered in the development of the plan runoff control strategy. Proof of no harm would have to be shown from the development site through the remainder of the downstream drainage network to the confluence of the creek with the Delaware or Lehigh River. Proof of no harm must be shown using the capacity criteria specified in § 205-16D if downstream capacity analysis is a part of the no harm justification.
The peak flow values to be used for downstream areas for the design return period storms (two-, ten-, twenty-five-, and one-hundred-year) shall be the values from the calibrated PSRM Model for the Bushkill Creek or as calculated by an applicant using an alternate method acceptable to the municipality. The flow values from the PSRM Model would be supplied to the developer by the municipality upon request.
Developer-proposed runoff controls which would generate increased peak flow rates at storm drainage problem areas would, by definition, be precluded from successful attempts to prove no harm, except in conjunction with proposed capacity improvements for the problem areas consistent with § 205-16P.
Any no harm justifications shall be submitted by the developer as part of the drainage plan submission per Article IV. Developers submitting no harm justifications must still meet all of the water quality requirements in § 205-14.
In certain instances, primarily within the conditional/provisional no detention areas, local drainage conditions may dictate more stringent levels of runoff control than those based upon protection of the entire watershed. In these instances, if the developer could prove that it would be feasible to provide capacity improvements to relieve the capacity deficiency in the local drainage network, then the capacity improvements could be provided by the developer in lieu of runoff controls on the development site. Peak flow calculations shall be done assuming that the local watershed is in the existing condition and then assuming that the local watershed is developed per current zoning and using the specified runoff controls. Any capacity improvements would be designed using the larger of the above peak flows and the capacity criteria specified in § 205-16D. All new development in the entire subarea(s) within which the proposed development site is located shall be assumed to implement the developer's proposed discharge control, if any.
Capacity improvements may also be provided as necessary to implement any regional detention alternatives or to implement a modified no harm option which proposes specific capacity improvements to provide that a less stringent discharge control would not create any harm downstream.
Infiltration BMP loading rate percentages in the Recommendation Chart for Infiltration Stormwater Management BMPs in Carbonate Bedrock in Appendix D shall be calculated as follows:
Soil thickness.
Soil thickness is to be measured from the bottom of any proposed infiltration system. The effective soil thickness in the Recommendation Chart for Infiltration Stormwater Management BMPs in Carbonate Bedrock in Appendix D is the measured soil thickness multiplied by the thickness factor based on soil permeability (as measured by the adapted 25 Pa. Code § 73.15 percolation test in Appendix G), as follows:
Permeability Range* (inches/hour)
6.0 to 12.0 0.8
2.0 to 6.0 1.0
1.0 to 2.0 1.4
0.75 to 1.0 1.2
0.5 to 0.75 1.0
* If the permeability rate (as measured by the adapted 25 Pa. Code § 73.15 percolation test in Appendix G) falls on a break between two thickness factors, the smaller thickness factor shall be used.
All stormwater detention facilities shall provide a minimum 1.0 foot freeboard above the maximum pool elevation associated with the two-year through twenty-five-year runoff events. A 0.5 foot freeboard shall be provided above the maximum pool elevation of the one-hundred-year runoff event. The freeboard shall be measured from the maximum pool elevation to the invert of the emergency spillway. The two-year through one-hundred-year storm events shall be controlled by the primary outlet structure. An emergency spillway for each basin shall be designed to pass the one-hundred-year return frequency storm peak basin inflow rate with a minimum 0.5 foot freeboard measured to the top of basin. The freeboard criteria shall be met considering any off-site areas tributary to the basin as developed, as applicable. If this detention facility is considered to be a dam as per DEP Chapter 105, the design of the facility must be consistent with the Chapter 105 regulations, and may be required to pass a storm greater than the one-hundred-year event.
The minimum circular orifice diameter for controlling discharge rates from detention facilities shall be three inches. Designs where a lesser size orifice would be required to fully meet release rates shall be acceptable with a three-inch orifice, provided that as much of the site runoff as practical is directed to the detention facilities. The minimum three-inch diameter does not apply to the control of the WQv.
Type II twenty-four-hour rainfall distribution.
Runoff calculations using the Soil-Cover-Complex Method shall use the Natural Resources Conservation Service Type II twenty-four-hour rainfall distribution. The twenty-four-hour rainfall depths for the various return periods to be used consistent with this chapter may be taken from NOAA Atlas 14, Volume 2, Version 2.1, 2004 or the PennDOT Intensity — Duration — Frequency Field Manual ("PDT-IDF") (May 1986) for Region 4. The following values are taken from the PDT-IDF Field Manual:
24-Hour Rainfall Depth (inches)
1-year 2.40
2-year 3.00
5-year 3.60
10-year 4.56
25-year 5.52
50-year 6.48
100-year 7.44
A graphical and tabular presentation of the Type II twenty-four-hour distribution is included in Appendix C.
Runoff calculations using the Rational Method shall use rainfall intensities consistent with appropriate times of concentration and return periods and NOAA Atlas 14, Volume 2, Version 2.1, 2004 or the Intensity-Duration-Frequency Curves as presented in Appendix C.
Runoff curve numbers (CNs) to be used in the Soil-Cover-Complex Method shall be based upon the matrix presented in Appendix C.
Pipe flow travel times shall be determined from velocities calculated using the Manning Equation assuming full flow and the Manning 'n' values from Appendix C.