A. 
All regulated earth disturbance activities within the municipality shall be designed, implemented, operated and maintained to meet the purposes of this Part, through these two elements:
(1) 
Erosion and sediment control during the earth disturbance activities (e.g., during construction); and
(2) 
Water quality protection measures after completion of earth disturbance activities (e.g., after construction), including operations and maintenance.
B. 
No regulated earth disturbance activities within the municipality shall commence until the requirements of this Part are met.
C. 
Erosion and sediment control during regulated earth disturbance activities shall be addressed as required by § 203-13.
D. 
Post-construction water quality protection shall be addressed as required by § 203-14. Operations and maintenance of permanent stormwater BMPs shall be addressed as required by Article IV.
E. 
All best management practices (BMPs) used to meet the requirements of this Part shall conform to the state water quality requirements, and any more-stringent requirements as determined by the municipality.
F. 
Techniques described in Appendix A (Low-Impact Development Practices) of this Part[1] are encouraged, because they reduce the costs of complying with the requirements of this Part and the state water quality requirements.
[1]
Editor's Note: Appendix A is included as an attachment to this chapter.
G. 
Written notification must be provided to adjacent property owners by the applicant of an earth disturbance activity or regulated activity when stormwater flows onto their property may be altered. A copy of the notification must be provided to the Township.
The following permit requirements may apply to certain regulated earth disturbance activities and must be met prior to commencement of regulated earth disturbance activities, as applicable:
A. 
All regulated earth disturbance activities subject to permit requirements by the DEP under regulations at 25 Pa. Code, Chapter 102.
B. 
Work within natural drainageways subject to permit by the DEP under 25 Pa. Code, Chapter 105.
C. 
Any stormwater management facility that would be located in or adjacent to surface waters of the commonwealth, including wetlands, subject to permit by the DEP under 25 Pa. Code, Chapter 105.
D. 
Any stormwater management facility that would be located on a state highway right-of-way, or require access from a state highway, shall be subject to approval by the Pennsylvania Department of Transportation (PennDOT).
E. 
Culverts, bridges, storm sewers or any other facilities which must pass or convey flows from the tributary area and any facility which may constitute a dam subject to permit by the DEP under 25 Pa. Code, Chapter 105.
A. 
No regulated earth disturbance activities within the municipality shall commence until approval by the municipality, and/or Montgomery County Conservation District, of an erosion and sediment control plan for construction activities.
B. 
DEP has regulations that require an erosion and sediment control plan for any earth disturbance activity of 5,000 square feet or more, under 25 Pa. Code, § 102.4(b).
C. 
In addition, under 25 Pa. Code, Chapter 92, a DEP NPDES construction activities permit is required for regulated earth disturbance activities.
D. 
Evidence of any necessary permit(s) for regulated earth disturbance activities from the appropriate DEP regional office or County Conservation District 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 A.
E. 
A copy of the erosion and sediment control plan and any required permit, as required by DEP regulations, shall be available at the project site at all times.
F. 
The choice and design of stormwater management systems used to meet the requirements of this section shall be based on the system types and specifications set forth in the Pennsylvania Handbook of Best Management Practices for Developing Areas, published by the Commonwealth of Pennsylvania. Various combinations of methods should be tailored to suit the particular requirements for the type of development and the local site conditions and approved by the Municipal Engineer.
G. 
The choice and design of stormwater management systems are to be developed through a procedure that selects best management practices and incorporates a combination of the following:
(1) 
Seeking to control runoff at its source through infiltration.
(2) 
Improving the quality of the stormwater conveyance.
(3) 
Providing for detention.
H. 
The rate of stormwater runoff from any subdivision or land development shall not exceed the rate of runoff prior to development. Requirements for design of stormwater management systems to control the quantity of discharge are outlined in this chapter. The distribution of drainage discharge from the development properties shall replicate that of before-development conditions to the maximum extent possible. The methodology and facilities used shall be based on the calculated flows and conditions of each particular site.
I. 
The stormwater management plan for each subdivision or land development proposal shall take into account and provide for the peak rate and volume flows to other areas in the watershed to ensure that cumulative problems are not increased as a result of flows from the proposed project. This analysis shall also explore possibilities to share stormwater management facilities with other areas in the watershed.
J. 
Recharge facilities, detention facilities, storm sewers, culverts, bridges, and related drainage installations shall be designed and constructed to meet the following purposes:
(1) 
To permit unimpeded flow of natural watercourses. Such flow may be redirected as required, subject to the approval of the Pennsylvania Department of Environmental Protection.
(2) 
To ensure adequate drainage of all low points as may be related to the street.
(3) 
To intercept stormwater runoff along streets at intervals reasonably related to the extent and grade of the area drained to prevent flow of stormwater across intersections during the design storm.
(4) 
To ensure adequate and unimpeded flow of stormwater under driveways in, near, or across natural watercourses or drainage swales. Pipes or other conduits sized to convey the proper design storm shall be provided as necessary.
(5) 
To prevent excessive flow on or across streets, sidewalks, drives, parking areas and any other paved surface or accessway.
K. 
To this end, the storm drainage system serving the street shall be designed to collect water at any point where three to five cubic feet per second is accumulated where water floods more than 1/2 of the roadway, and the low point of all vertical grades, 100 feet upgrade of each low point and immediately upgrade of all street intersections. The system shall discharge any collected water which is not recharged into the nearest practical natural drainage channel or stormwater system.
L. 
All natural watercourses or concentrations of surface water shall be maintained in their existing condition, unless alteration is approved by the municipality. In any event, all encroachment activities shall comply with Chapter 105 of the Commonwealth of Pennsylvania Department of Environmental Protection's Dam Safety and Waterway Management Rules and Regulations.
M. 
Man-made structures shall be kept to a minimum, and bridges, culverts, or riprap shall be constructed to maintain natural characteristics of the stream and shall meet the approval of the municipality. Retention/detention basins shall be designed to utilize the natural contours of the land. When such design is impracticable, the construction of the basin design shall utilize slopes as shallow as possible to blend the structures into the existing terrain. The use of multiple retention/detention facilities, which are smaller and less intrusive on the site, is encouraged.
N. 
The municipality may require that a landowner or developer provide reasonable corrective on-site measures to alleviate any existing off-site drainage problem which may be affected by the proposed subdivision and/or land development. If off-site easements are required, it shall be the responsibility of the landowner or developer to obtain all drainage easements on, over, or through other properties, and the municipality, its agents, workmen, and employees shall be indemnified and held harmless from any liability. Any water originating from nonnatural sources, such as swimming pools, air-conditioning units, sump pumps, roof drains, or other similar flow, shall be properly discharged into a recharge facility or natural watercourses on the property or connected to an existing or proposed storm drainage system as approved by the municipality. This discharge shall not be discharged to adjacent properties. Polluting matter from such sources may not be deposited into natural watercourses or storm drains.
O. 
Where possible, building foundations, grade slabs, and cellar floors located in soils that have a community development limitation degree of moderate to severe seasonal high-water table (as defined in the Montgomery County Soil Survey) shall be provided with an underdrain system. This system shall provide for drainage of the enclosed volume above the slab and relief of subsurface water to a depth of not less than 18 inches below the slab or foundation field of the herringbone or gridiron configuration in coarse, gravel-filled trenches that are in direct contact with the slab or foundation subbase. The excavation shall provide a minimum of 0.05 foot/foot slope to the gravel-filled trenches.
P. 
To mitigate the potential polluting of surfacewaters and groundwaters by pollutants such as salt, petroleum products, and antifreeze flowing from paved parking lots, pretreatment of the runoff shall be required. The extent of the treatment shall be set by the Municipal Engineer and will be determined by such factors as the area of the parking lot and the course of the runoff as it is recharged or flows into natural waterways.
Q. 
During site construction, all recharge system components shall be protected from compaction due to heavy equipment operation or storage of fill or construction material. Recharge areas shall also be protected from sedimentation. All areas designated for recharge shall not receive runoff until the contributory drainage area has achieved final stabilization or shall be cleared and reconstructed at that time.
(1) 
The following procedures and materials shall be required during the construction of all subsurface facilities:
(a) 
Excavation for the infiltration facility shall be performed with equipment which will not compact the bottom of the seepage bed/trench or like facility.
(b) 
The bottom of the bed and/or trench shall be scarified prior to the placement of aggregate.
(c) 
Only clean aggregate, free of fines, shall be allowed.
(d) 
The top and sides of all seepage beds, trenches, or like facilities shall be covered with drainage filtration fabric. Fabric shall meet the specifications of PennDOT Publication 408, Section 735, Construction Class 1.
(e) 
Perforated distribution pipes connected to centralized catch basins and/or manholes with provision for the collection of debris shall be provided in all facilities. The perforated pipes shall distribute stormwater throughout the entire seepage bed/trench or like facility.
R. 
Standards during land disturbance.
(1) 
During the period of land disturbance, when significant sediment can be contained in runoff, this runoff shall be controlled prior to entering any proposed infiltration area.
A. 
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 after construction is complete.
B. 
The BMPs must be designed, implemented and maintained to meet state water quality requirements, and any other more-stringent requirements as determined by the municipality.
C. 
To control post-construction 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 post-construction stormwater discharges do not degrade the physical, chemical or biological characteristics of the receiving waters. As described in the DEP Comprehensive Stormwater Management Policy (No. 392-0300-002, September 28, 2002), this may be achieved by the following:
(1) 
Infiltration: replication of preconstruction stormwater infiltration conditions;
(2) 
Treatment: use of water quality treatment BMPs to ensure filtering out of the 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).
D. 
The DEP has regulations that require municipalities to ensure design, implementation and maintenance of best management practices ("BMPs") that control runoff from new development and redevelopment after regulated earth disturbance activities are complete. These requirements include the need to implement post-construction stormwater BMPs with assurance of long-term operations and maintenance of those BMPs.
E. 
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 A.
F. 
BMP operations and maintenance requirements are described in Article IV of this Part.
G. 
After installation of impervious cover, there shall be no increase in the volume of stormwater runoff being discharged for up to the two-year frequency rainfall, predevelopment to post-development. If the Municipal Engineer determines that such a standard is not achievable on the site (all or in part) based on the existing soil, bedrock, water table, or other conditions on the parcel, provisions listed in Subsection I apply. For preliminary design purposes, this volume can be initially estimated as a depth of 2.5 inches per unit area of new impervious surface.
H. 
After installation of impervious cover and assuming full compliance with Subsection G, the peak rate of stormwater discharges from the site for all design storms up to and including a one-hundred-year frequency rainfall shall not exceed the peak discharges from the site of the same storm before disturbance. Design storms include:
(1) 
Two-year, twenty-four-hour storm.
(2) 
Ten-year, twenty-four-hour storm.
(3) 
Twenty-five-year, twenty-four-hour storm.
(4) 
Fifty-year, twenty-four-hour storm.
(5) 
One-hundred-year, twenty-four-hour storm.
I. 
If the volume set forth in Subsection G cannot be achieved, then the peak rate standards are modified so the post-development peak rate discharges from the site for all storms up to the ten-year storm must be equal to or less than 75% the respective peak rates for these storms predevelopment.
J. 
Under certain conditions, the municipality, upon recommendation of the Municipal Engineer, may impose the following additional restrictions on stormwater discharges:
(1) 
Peak discharge may be further restricted to alleviate off-site drainage problems.
(2) 
Measures shall be imposed to protect against groundwater or surface water pollution where the type of business activity may result in significant non-point-source pollution ("hot spots") or the nature of the soils or bedrock underlying a stormwater management structure constitutes substantial risk of contamination, such as might be the case in limestone formations. Special provisions to be followed in these cases will be provided by the Municipal Engineer.
(3) 
Where groundwater yields are very low or where a groundwater supply already is heavily used, the municipality may require that the entire volume of the two-year frequency rainfall (3.2 inches in 24 hours) be retained and infiltrated.