A. The City of Reading is comprised of two watersheds: Tulpehocken Creek and Schuylkill River. Additionally, each of these watersheds has been divided into stormwater management districts as shown on the Management District Map in Appendix D.
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(2) Standards for managing runoff from each subarea in the Schuylkill River Watershed for the two-year through one-hundred-year design storms are shown in Tables 505-128.1 and 505-128.2. Development sites located in each of the districts must control proposed conditions runoff rates to existing conditions runoff rates for the design storms in accord with Tables 505-128.1 and 505-128.2.
Table 505-128.1
Water Quantity Requirements for Areas in the Schuylkill River Watershed
Water Quantity Requirements for Areas in the Schuylkill River Watershed
Management District | Proposed Condition Design Storm | Existing Condition Design Storm | Equivalent Release Rate |
Management District | Proposed Condition Design Storm | Existing Condition Design Storm | Equivalent Release Rate | |
A | 2-year | Reduce to | 1-year | — |
5-year | 5-year | 100% | ||
10-year | 10-year | 100% | ||
25-year | 25-year | 100% | ||
50-year | 50-year | 100% | ||
100-year | 100-year | 100% | ||
B | 2-year | Reduce to | 1-year | — |
5-year | 2-year | 30% | ||
10-year | 5-year | 75% | ||
25-year | 10-year | 75% | ||
50-year | 25-year | 75% | ||
100-year | 50-year | 75% | ||
C | 2-year | Reduce to | 2-year | — |
5-year | 5-year | 100% | ||
10-year | 10-year | 100% | ||
25-year | 25-year | 100% | ||
50-year | 50-year | 100% | ||
100-year | 100-year | 100% | ||
Table 505-128.2
Water Quantity Requirements for Areas in the Tulpehocken Creek Watershed
Water Quantity Requirements for Areas in the Tulpehocken Creek Watershed
Management District | Design Storm Post- Development | Design Storm Pre- Development |
Management District | Design Storm Post- Development | Design Storm Pre- Development | |
A | 2-year | Reduce to | 1-year |
5-year | 5-year | ||
10-year | 10-year | ||
25-year | 25-year | ||
B1 | 2-year | Reduce to | 1-year |
5-year | 2-year | ||
10-year | 5-year | ||
25-year | 10-year | ||
B2 | 2-year | Reduce to | 1-year |
5-year | 2-year | ||
10-year | 5-year | ||
25-year | 10-year | ||
100-year | 100-year | ||
C | 2-year | Reduce to | 1-year |
5-year | 2-year | ||
(3) For any site which proposes direct discharge, the site may only utilize any available capacity in the downstream conveyance system which is equivalent to the ratio of the proposed development site acreage to the total watershed acreage to the downstream conveyance system. Therefore, if the proposed development site is 10% of the total watershed area, the increase in runoff may only use up 10% of the documented available downstream, capacity at peak flow.
B. General. Proposed condition rates of runoff from any regulated activity shall not exceed the peak release rates of runoff prior to development for the design storms specified on the Stormwater Management District Watershed Map (Appendix D) and § 505-128, of this Part.
C. District boundaries. The boundaries of the stormwater management districts are shown on an Official Map that is available for inspection at the municipal office. A copy of the Official Map at a reduced scale is included in the Appendix D. The exact location of the stormwater management district boundaries as they apply to a given development site shall be determined by mapping the boundaries using the two-foot topographic contours (or most accurate data required) provided as part of the drainage plan.
D. Sites located in more than one district. For a proposed development site located within two or more stormwater management district category subareas, the peak discharge rate from any subarea shall meet the management district criteria for which the discharge is located, as indicated in § 505-128. The calculated peak discharges shall apply regardless of whether the grading plan changes the drainage area by subarea. An exception to the above may be granted if discharges from multiple subareas recombine in proximity to the discharge site. In this case, peak discharge in any direction shall follow Management District A criteria, provided that the overall site discharge meets the management district criteria for which the discharge is located.
E. Off-site areas. Off-site areas that 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.
F. Site areas. Where the site area to be impacted by a proposed development activity differs significantly from the total site area, only the proposed impact area utilizing stormwater management measures shall be subject to the management district criteria. In other words, unimpacted areas bypassing the stormwater management facilities would not be subject to the management district criteria.
G. "No harm" option. For any proposed development site not located in a provisional direct discharge district, the applicant has the option of using a less-restrictive runoff control (including no detention) if the applicant can prove that "no harm" would be caused by discharging at a higher runoff rate than that specified by the stormwater management plan. The "no harm" option is used when an applicant can prove that the proposed condition hydrographs can match existing conditions hydrographs, or if it can be proved that the proposed conditions will not cause increases in peaks at all points downstream. Proof of "no harm" must be shown based upon the following downstream impact evaluation, which shall include a downstream hydraulic capacity analysis consistent with Subsection H to determine if adequate hydraulic capacity exists. The applicant shall submit to the municipality this evaluation of the impacts due to increased downstream stormwater flows in the watershed.
(1) The hydrologic regime of the site must be maintained.
(2) The downstream impact evaluation shall include hydrologic and hydraulic calculations necessary to determine the impact of hydrograph timing modifications due to the proposed development upon a dam, highway, structure, natural point of restricted streamflow or any stream channel section, established with the concurrence of the municipality.
(3) The evaluation shall continue downstream until the increase in flow diminishes due to additional flow from tributaries and/or stream attenuation.
(4) The peak flow values to be used for downstream areas for the design return period storms (two-, five-, ten-, twenty-five-, fifty-, and one-hundred-year) shall be the values from the calibrated model for the applicable (Schuylkill River or Tulpehocken Creek) watershed. These flow values can be obtained from the original Act 167 watershed stormwater management plans.
(5) Applicant-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 § 505-128H.
(6) A financial distress shall not constitute grounds for the municipality to approve the use of the no-harm option.
(7) Capacity improvements may be provided as necessary to implement the no-harm option, which proposes specific capacity improvements to provide that a less stringent discharge control would not create any harm downstream.
(8) Any no-harm justifications shall be submitted by the applicant as part of the drainage plan submission per Subpart D.
H. Downstream hydraulic capacity analysis. Any downstream capacity hydraulic analysis conducted in accordance with this Part shall use the following criteria for determining adequacy for accepting increased peak flow rates:
(1) Natural or man-made channels or swales must be able to convey the increased runoff associated with a two-year return period event within their banks at velocities consistent with protection of the channels from erosion. Acceptable velocities shall be based upon criteria included in the DEP Erosion and Sediment Pollution Control Program Manual.
(2) Natural or man-made channels or swales must be able to convey the increased twenty- five-year return period runoff without creating any hazard to persons or property.
(3) Culverts, bridges, storm sewers or any other facilities which must pass or convey flows from the tributary area must be designed in accordance with DEP Chapter 105 regulations (if applicable) and, at minimum, pass the increased twenty-five-year return period runoff.
I. Regional detention alternatives. For certain areas within the study area, it may be more cost-effective to provide one control facility for more than one development site than to provide an individual control facility for each development site. The initiative and funding for any regional runoff control alternatives are the responsibility of the prospective applicants. The design of any regional control basins must incorporate reasonable development of the entire upstream watershed. The peak outflow of a regional basin would be determined on a case-by-case basis using the hydrologic model of the watershed consistent with protection of the downstream watershed areas. "Hydrologic model" refers to the calibrated model as developed for the stormwater management plan.
J. Hardship option. The municipality may hear requests for waivers where it is alleged that the provisions of this (Act 167) Part inflict unnecessary hardship upon the applicant. The waiver request shall be in writing and accompanied by the requisite fee based upon a fee schedule adopted by the municipality. A copy of the waiver request shall be provided to each of the following: municipality, Municipal Engineer, Municipal Solicitor and Berks County Planning Commission. The request shall fully document the nature of the alleged hardship. The municipality may grant a waiver, provided that all of the following findings are made in a given case:
(1) That there are unique physical circumstances or conditions, including irregularity of lot size or shape, or exceptional topographical or other physical conditions peculiar to the particular property, and that the unnecessary hardship is due to such conditions, and not the circumstances or conditions generally created by the provisions of this Part in the stormwater management district in which the property is located.
(2) That because of such physical circumstances or conditions, there is no possibility that the property can be developed in strict conformity with the provisions of this Part, including the no-harm provisions, and that the authorization of a waiver is therefore necessary to enable the reasonable use of the property.
(3) That such unnecessary hardship has not been created by the applicant.
(4) That the waiver, if authorized, will represent the minimum waiver that will afford relief and will represent the least modification possible of the regulation in issue.
(5) That financial hardship is not the criteria for granting of a hardship waiver. In granting any waiver, the municipality may attach such conditions and safeguards as it may deem necessary to implement the purposes of Act 167 and this Part. If a hardship waiver is granted, the applicant must still manage the quantity, velocity, direction and quality of resulting storm runoff as is necessary to prevent injury to health, safety or other property.
(a) For regulated activities in § 505-105D(1) and (2), the Planning Commission shall hear requests for and decide on hardship waiver requests on behalf of the municipality.
(b) For regulated activities in § 505-105D(4), (5), (6), (7) and (8), the Municipal Engineer shall hear requests for and decide on hardship waiver requests on behalf of the municipality.
(c) The municipality shall not waive the water quality provisions of this Part.
11. Editor's Note: Appendix D is included at the end of this chapter.