STORMWATER MANAGEMENT REQUIREMENTS FOR HOGESTOWN RUN AND
TRINDLE SPRING RUN
§101. General Provisions
§103. Stormwater Management
§104. Drainage Plan Requirements
§105. Schedule of Inspections
§106. Fees and Expenses
§107. Maintenance Responsibilities
§108. Enforcement and Penalties
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STORMWATER MANAGEMENT REQUIREMENTS FOR HOGESTOWN RUN AND
TRINDLE SPRING RUN
§101. GENERAL PROVISIONS.
1. Statement of Findings. The Board of Township Commissioners of the Township of
Hampden hereby finds that:
A. Inadequate management of accelerated stormwater runoff resulting from development throughout a watershed increases flood flows and velocities, contributes to erosion and sedimentation, overtaxes the carrying capacity of existing streams and storm sewers, greatly increases the cost of public facilities to convey and manage stormwater, undermines floodplain management and flood reduction efforts in upstream and downstream communities, reduces groundwater recharge, and threatens public health and safety.
B. A comprehensive program of stormwater management, including reasonable regulation of development and activities causing accelerated erosion, is fundamental to the public health, safety, welfare and the protection of the people of the Township and all the people of the Commonwealth, their resources and the environment.
2. Purpose. The purpose of this Part is to promote health, safety and welfare only within the Hogestown Run Watershed and Trindle Spring Run Watershed to the extent that such watersheds exist within the Township of Hampden by minimizing the damages described in §101(1)(A) of this Part through provisions designed to:
A. Manage accelerated runoff and erosion and sedimentation problems at their source by regulating activities that cause these problems.
B. Utilize and preserve the existing natural drainage systems.
C. Encourage recharge of groundwater where appropriate and prevent degradation of groundwater quality.
D. Maintain existing flows and quality of streams and watercourses in the Township and the Commonwealth.
E. Preserve and restore the flood carrying capacity of streams.
F. Provide proper maintenance of all permanent stormwater management facilities that are constructed in the Township.
G. Provide performance standards and design criteria for stormwater management and planning.
3. Statutory Authority. The Township is empowered to regulate land use activities that affect runoff by the authority of the Act of October 4, 1978, P.L. 864 (Act 167), the “Stormwater Management Act.”
4. Applicability. This Part shall only apply to permanent stormwater management facilities constructed as part of any of the regulated activities listed in this Section. Stormwater management and erosion and sedimentation control during construction activities are specifically not regulated by this Part, but shall continue to be regulated under existing laws and ordinances. The following activities are defined as “regulated activities” and shall be regulated by this Part:
A. Land development.
C. Construction of new or additional impervious or semi-pervious surfaces (driveways, parking lots, etc.).
D. Construction of new buildings or additions to existing buildings.
E. Diversion or piping of any natural or manmade stream channel.
F. Installation of stormwater management facilities or appurtenances thereto.
within the Hogestown Run Watershed and Trindle Spring Run Watershed to the extent that such watersheds exist within the Township of Hampden.
(Ord. 95-9, 8/31/1995, Art. I)
1. For the purposes of this Part, certain terms and words used herein shall be interpreted as follows
A. Words used in the present tense include the future tense; the singular number includes the plural and the plural number includes the singular; words of masculine gender include feminine gender; and words of feminine gender include masculine gender.
B. The word “includes” or “including” shall not limit the term to the specific example but is intended to extend its meaning to all other instances of like kind and character.
C. The word “person” includes an individual, firm, association, organization, partnership, trust, company, corporation or any other similar entity.
D. The words “shall” and “must” are mandatory; the words “may” and “should” are permissive.
E. The words “used or occupied” include the words “intended, designed, maintained, or arranged to be used or occupied.”
2. Specific Terms.
ALTERATION ‑ as applied to land, a change in topography as a result of the moving of soil and rock from one location or position to another; also the changing of surface conditions by causing the surface to be more or less impervious; land disturbance.
APPLICANT ‑ a landowner or developer who has filed an application for approval to engage in any regulated activities as defined in §101(4) of this Part.
CISTERN ‑ an underground reservoir or tank for storing rainwater.
CONSERVATION DISTRICT ‑ the Cumberland County Conservation District.
CULVERT ‑ a structure with appurtenant works which carries a stream under or through an embankment or fill.
DAM ‑ an artificial barrier, together with its appurtenant works, constructed for the purpose of impounding or storing water or another fluid or semi-fluid, or a refuse bank, fill or structure for highway, railroad or other purposes which does or may impound water or another fluid or semi-fluid.
DESIGN STORM ‑ the magnitude and temporal distribution of precipitation from a storm event measured in probability of occurrence (e.g. a 5-year storm) and duration (e.g. 24 hours), used in the design and evaluation of stormwater management systems.
DETENTION BASIN ‑ an impoundment structure designed to manage stormwater runoff by temporarily storing the runoff and releasing it at a predetermined rate.
DEVELOPER ‑ a person, partnership, association, corporation or other entity, or any responsible person therein or agent thereof, that undertakes any regulated activity of this Part.
DEVELOPMENT SITE ‑ the specific tract of land for which a regulated activity is proposed.
DRAINAGE EASEMENT ‑ a right granted by a landowner to a grantee, allowing the use of private land for stormwater management purposes.
DRAINAGE PLAN ‑ the documentation of the stormwater management system, if any, to be used for a given development site, the contents of which are established in §104(3).
EROSION ‑ the movement of soil particles by the action of water, wind, ice or other natural forces.
FLOODPLAIN ‑ any land area susceptible to inundation by water from any natural source or delineated by applicable Department of Housing and Urban Development, Federal Insurance Administration Flood Hazard Boundary Maps as being a special flood hazard area. Also included are areas that comprise Group 13 Soils, as listed in Appendix A of the Pennsylvania Department of Environmental Protection (PA DEP) “Technical Manual for Sewage Enforcement Officers” (as amended or replaced from time to time by PA DEP).
GROUNDWATER RECHARGE ‑ replenishment of existing natural underground water supplies.
IMPERVIOUS SURFACE ‑ a surface that prevents the percolation of water into the ground.
INFILTRATION STRUCTURES ‑ a structure designed to direct runoff into the ground (e.g. french drains, seepage pits, seepage trench).
LAND DEVELOPMENT ‑
(1) The improvement of one lot or two or more contiguous lots, tracts or parcels of land for any purpose involving (a) a group of two or more buildings, or (b) the division or allocation of land or space between or among two or more existing or prospective occupants by means of, or for the purpose of streets, common areas, leaseholds, condominiums, building groups or other features.
(2) Any subdivision of land.
(3) Any lot improvements regulated under the Township Zoning Regulations [Chapter 27].
LAND DISTURBANCE ‑ any activity involving grading, tilling, digging or filling of ground or stripping of vegetation or any other activity that causes an alteration to the natural condition of the land.
MUNICIPALITY ‑ Township of Hampden in Cumberland County, Pennsylvania.
OPEN CHANNEL ‑ a drainage element in which stormwater flows with an open surface. Open channels include, but shall not be limited to, natural and manmade drainage ways, swales, streams, ditches, canals and pipes flowing partly full.
PA DEP ‑ Pennsylvania Department of Environmental Protection. [Ord. 98-7]
PLAN ADMINISTRATOR ‑ the entity set up specifically to review drainage plans, inspect stormwater management structures and otherwise enforce all regulations as outlined in this Part.
PEAK DISCHARGE ‑ the maximum rate of stormwater runoff from a specified storm event.
PIPE ‑ a culvert, closed conduit or similar structure (including appurtenances) that conveys stormwater.
PMF PROBABLE MAXIMUM FLOOD ‑ the flood that may be expected from the most severe combination of critical meteorologic and hydrologic conditions that are reasonably possible in an area. The PMF is derived from the probable maximum precipitation (PMP) as determined on the basis of data obtained from the National Oceanographic and Atmospheric Administration (NOAA).
REGULATED ACTIVITIES ‑ actions or proposed actions that have an impact on stormwater runoff and that are specified in §101(4) of this Part.
RETENTION BASIN ‑ an impoundment in which stormwater is stored and not released during the storm event. Stored water may be released from the basin at some time after the end of the storm.
RETURN PERIOD ‑ the average interval, in years, within which a storm event of a given magnitude can be expected to recur. For example, the 25 year return period rainfall would be expected to recur on the average once every 25 years.
RUNOFF ‑ any part of precipitation that flows over the land surface.
SCS ‑ U.S. Department of Agriculture, Soil Conservation Service.
SEDIMENTATION ‑ the process by which mineral or organic matter is accumulated or deposited by the movement of water.
SEDIMENT BASIN ‑ a barrier, dam, retention or detention basin located and designed to retain rock, sand, gravel, silt or other material transported by water.
SEEPAGE PIT/SEEPAGE TRENCH ‑ an area of excavated earth filled with loose stone or similar coarse material into which surface water is directed for infiltration into the ground.
SOIL‑COVER COMPLEX METHOD ‑ a method of runoff computation developed by the SCS that is based on relating soil type and land use/cover to a runoff parameter called a Curve Number (CN).
STORAGE INDICATION METHOD ‑ a reservoir routing procedure based on solution of the continuity equation (inflow minus outflow equals the change in storage) with outflow defined as a function of storage volume and depth.
STORM SEWER ‑ a system of pipes and/or open channels that convey intercepted runoff and stormwater from other sources, but excludes domestic sewage and industrial wastes.
STORMWATER ‑ the total amount of precipitation reaching the ground surface.
STORMWATER MANAGEMENT FACILITY ‑ any structure, natural or manmade, that, due to its condition, design or construction, conveys, stores or otherwise affects stormwater runoff. Typical stormwater management facilities include, but are not limited to, detention and retention basins, open channels, storm sewers, pipes and infiltration structures.
STORMWATER MANAGEMENT PLAN ‑ the plan for managing stormwater runoff.
STREAM ENCLOSURE ‑ a bridge, culvert or other structure in excess of 100 feet in length upstream to downstream which encloses a regulated water of this Commonwealth.
SUBDIVISION ‑ the division or re‑division of a lot, tract or parcel of land by any means into two or more lots, tracts, parcels or other divisions of land including changes in existing lot lines for the purpose, whether immediate or future, of lease, transfer of ownership, or building or lot development.
WETLAND ‑ those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions, including swamps, marshes, bogs, ferns and similar areas.
(Ord. 95-9, 8/31/1995, Art. II; as amended by Ord. 98-7, 8/27/1998)
§103. STORMWATER MANAGEMENT.
1. General Requirements.
A. Stormwater drainage systems shall be provided in order to permit unimpeded flow along natural watercourses, except as modified by stormwater management facilities or open channels consistent with this Part.
B. The existing points of concentrated drainage that discharge onto adjacent property shall not be relocated and shall be subject to any applicable release rate criteria specified in this Part.
C. Areas of existing diffused drainage discharge shall be subject to any applicable release rate criteria in the general direction of existing discharge, whether proposed to be concentrated or maintained as diffused drainage areas. If diffused flow is proposed to be concentrated and discharged onto adjacent property, the developer must document that adequate downstream conveyance facilities exist to safely transport the concentrated discharge or otherwise prove that no erosion, sedimentation, flooding or other harm will result from the concentrated discharge.
D. Where a development site is transversed by watercourses other than permanent streams, a drainage easement shall be provided conforming substantially to the line of such watercourse. The terms of the easement shall prohibit excavation, the placing of fill or structures and any alterations that may adversely affect the flow of stormwater within any portion of the easement. Also, maintenance and mowing of vegetation within the easement shall be required.
E. Any stormwater management facilities regulated by this Part that would be located on State highway rights‑of‑way shall be subject to approval by the Pennsylvania Department of Transportation (PennDOT).
F. Any stormwater management facilities regulated by this Part that would be located in or adjacent to waters of the Commonwealth or potential wetlands shall be subject to approval by PA DEP through the joint permit application process. When there is a question as to whether wetlands may be involved, it is the responsibility of the developer or his agent to show that the land in question cannot be classified as wetlands, otherwise approval to work in the area must be obtained by PA DEP. [Ord. 98-7]
G. When it can be shown that, due to topographic conditions, natural drainage ways on the site cannot adequately provide for drainage, open channels may be constructed conforming substantially to the line and grade of such natural drainage ways.
H. Sinkholes shall be protected as follows:
(1) Stormwater from roadways, parking lots, storm sewers, roof drains or other concentrated runoff paths shall not be discharged directly into sinkholes.
(2) Sinkholes with sufficient capacity to receive appreciable amounts of storm- water shall be designated as such by posting onsite notices clearly visible at the sinkhole prohibiting any disposal of refuse, rubbish, hazardous wastes, organic matter or soil into the sinkhole. Rock fill may be permitted in the sinkhole for the purpose of preventing dumping of said materials. The discharge of stormwater runoff to the subsurface using sinkholes shall be considered as potential pollution and prohibited unless the disposal method is designed so that contaminants in the runoff will be absorbed/adsorbed in the soil mantle and be acted upon by the bacteria naturally present in the mantle before reaching the groundwater. Systems intended to meet this requirement shall be designed by a hydrogeologist.
(3) If increased or concentrated runoff is to be discharged into a sinkhole, including filtered discharge, a geologic assessment of the effects of such runoff on increased land subsidies and groundwater quality shall be prepared and the results submitted with the drainage plan. Such discharge shall be prohibited if the Township Engineer determines that the discharge poses a hazard to life, property or groundwater resources.
(1) Perform investigations for all subdivisions and land developments except minor construction projects such as residential building extensions or accessory structures to map the following karst features of feature indicators:
(a) Closed depressions.
(b) “Ghost lakes” after rainfall.
(c) Open sinkholes.
(d) Outcrops of bedrock.
(e) Seasonal high water table indicators.
(f) Surface drainage into ground.
(g) Unplowed areas in plowed fields.
The map shall be at the same scale as the development or subdivision plan. The map shall be prepared by an engineer/geologist with a minimum of 3 years of professional experience in preparing such maps. This map shall be prepared from but not necessarily limited to a review of aerial photographs, soils, maps, geologic and other similar related data. The engineer shall also conduct a site inspection of the property.
(2) Based upon the above preliminary work the engineer/geologist shall determine what further testing, if any, shall be performed by the developer to enable compliance with the geologic design standards set forth below. Testing methodology shall be reasonable and consistent under the circumstances, including (1) the scale of the proposed development and (2) the hazards revealed by examination of available data and site inspection.
(3) The geologic mapping and test results shall be submitted as part of the overall subdivision and land development plan data. The report shall address the capability of the site to support the proposed development in a manner in which the risks attendant to development in carbonate areas are either eliminated or minimized.
(4) Recommendations for site development relating to stormwater management facilities shall be included.
(5) Additional studies or testing as deemed necessary by the Township Engineer in order to produce an adequate study given the scale of the proposed development and the hazards revealed, may be required of the developer.
J. Geologic Design Standards:
(1) All stormwater management facilities and related structures shall be so situated, designed and constructed as to minimize the risk of structural damage from existing or future sinkholes.
(2) Stormwater management facilities such as groundwater recharge pits, beds or trenches and detention ponds shall not be located within 100 feet of the karst features identified above in subsection (1) unless (1) the engineer/geologist demonstrates that a minimal risk of structural damage due to sinkholes will exist or (2) mitigating measures are taken to minimize the risk of structural damage. These mitigating measures shall be designed by developer’s engineer/geologist. Stormwater shall not be redirected into a sinkhole.
2. Stormwater Management Performance Standards.
A. The applicable performance standards for managing runoff from each sub area in the Hogestown Run/Trindle Spring Run watersheds for the 2, 10 and 25 year design storms are provided in the release rate table on Plate 4 of this Part. Post-development peak flows at the mouth of each of the sub-areas, shown on Plate 4 must not exceed the arithmetic product of the applicable sub-area release rate times the predevelopment peak flow from the particular site under consideration.
B. The peak discharge for each sub-area in either watershed shall be calculated based upon the weighted CN which has been adjusted in accordance with the following equations:
(1) Trindle Spring Run.
Adjusted CN = (1.3 x weighted CN)‑30, for the 2 and 25 year events.
Adjusted CN = (1.2 x weighted CN)‑20, for the 10 year events.
(2) Hogestown Run.
Adjusted CN = (1.1 x weighted CN)‑10, for the 2 and 25 year events.
Adjusted CN = (1.2 x weighted CN)‑20, for the 10 year events.
C. Stormwater management facilities that reduce post-development peak flows may not be required or be recommended for some sub-areas as specified on Plate 4 of this Part. However, the capacity of existing drainage facilities in these sub-areas may be inadequate for conveying post-development peak flows. Where the existing drainage facilities are inadequate for conveying post-development peak flows, the developer shall either release post-development peak flows at 100 percent of the existing peak flow or increase the conveyance capacity of the inadequate drainage elements as specified in this Part.
D. When post-development peak flows are released at 100% of the predevelopment peak, significant changes in the timing of post-development runoff shall not be permitted. The release of post-development peak flows at 100% of the predevelopment peak flow may increase the duration of the peak discharge from a site and may in turn increase peak discharges in an area that are located downstream of the site. Increases in peak discharges at downstream locations resulting from releasing post-development peaks at 100% of predevelopment peak flows shall not be permitted and an acceptable alternative stormwater management facility or technique or capacity improvements must be implemented as part of the development.
E. Within those watershed areas designated as “provisional no detention” the developer may discharge post‑development peak runoff directly into existing conveyance systems (detention facilities need not be constructed) provided there is no adverse affect on the total watershed peak flow. In certain instances, however, the “local” runoff conveyance facilities, which transport runoff from the site to the main channel, may not have adequate capacity to safely transport increased peak flows associated with not providing detention for a proposed development. In those instances, the developer shall either use a 100% release rate control or provide increased capacity of downstream drainage elements to convey increased peak flows consistent with §103(3)(I). In determining if adequate capacity exists in the existing local watershed drainage network, the developer must assume that the entire local watershed is developed per current zoning and that all new development would use the runoff controls specified by this Part. Similarly, any capacity improvement must be designed to convey runoff from development of all areas tributary to the improvement consistent with the capacity criteria specified in §103(3)(C).
3. Design Criteria for Stormwater Management Facilities.
A. Incorporate stormwater management techniques into the design to reduce the runoff volume and rate of discharge. (These techniques may include minimizing impervious surfaces, planting flat grassed waterways and using any other means to increase the time of concentration and filtration of the runoff.) Then compute and compare pre and post development runoff hydrographs at each point‑of‑ interest for the 2, 10 and 25 year events. When analysis indicates that the post‑development hydrographs and volumes are less than or equal to the pre‑development hydrographs in peak and volume, additional stormwater controls are not required for the portion of the site draining to the point‑ of‑interest. Stormwater detention facilities will be required, in addition to the stormwater management reduction techniques, when analysis illustrates that post-development peak runoff rates and volumes are greater than the predevelopment runoff rates and volumes. Design the detention facilities and related structures to release the 2, 10 and 25 year events in accordance with the performance standards found on Plate 4 and in other sections of this Part.
B. Rules and Regulations.
(1) PA DEP, Chapter 105, Rules and Regulations, apply to the construction, modification, operation or maintenance of both existing and proposed dams, water obstructions and encroachments throughout the watershed. Inquiries on permit requirements or other concerns should be addressed to the Southcentral Regional Office, One Ararat Boulevard, Room 147, Harrisburg, Pennsylvania 17110. [Ord. 98-7]
(2) Any stormwater management facility required or regulated by this Part shall be designed to provide an emergency spillway to handle flow up to the 100 year post-development conditions. The height of embankment must be set as to provide a minimum of 1 foot of freeboard above the maximum pool elevation computed when the facility functions for the 100 year post-development inflow. However, criteria for design and construction of stormwater management facilities are not the same criteria that are used in permitting of dams under the Dam Safety Program. Depending upon the physical characteristics of a dam, a dam permit may be required and the design will have to meet the provisions of Chapter 105 of the Dam Safety and Encroachments Act. Depending on the physical characteristics of a dam, the design could require that anywhere from a 50 year to a probable maximum flood storm event be considered.
C. Any hydraulic capacity analysis conducted in accordance with this Part shall use the following criteria to determine if adequate hydraulic capacity exists:
(1) Open channels must be able to convey post-development runoff from a 2 year design storm within their banks at velocities that would not erode the channel bed or banks. Acceptable velocities shall be based on criteria included in the PA DEP Soil Erosion and Sedimentation Control Manual (as amended or replaced from time to time by PA DEP) and presented in Table A‑4 in the Appendix of this Part. [Ord. 98-7]
(2) Open channels must be able to convey post-development runoff from a 100 year design storm within their banks with a minimum 1 foot of freeboard and not create hazard to any persons or property.
(3) Any other drainage conveyance facility that does not fall under Chapter 105 regulations must be able to convey, without damage to the drainage structure or roadway, runoff from the 25 year storm with a minimum 1.0 foot of freeboard measured below the lowest point along the top of the roadway. Any facility located within a PennDOT right‑of‑way must meet PennDOT minimum design standards and permit submission requirements.
(4) Storm sewer inlet spacing and road cross‑section design must ensure that post-development runoff resulting from 10 year design storm of 5 minute duration does not flood more than 1/2 of a traffic lane, i.e., excluding the parking lane.
(5) Storm sewers must be able to convey post-development runoff from a 25 year design storm without surcharging inlets. Prevent the exfiltration of stormwater from storm sewer pipes by providing a water tight seal at all pipe section junctions and at inlet boxes.
D. Easements along open channels shall be provided. The minimum width of the required easement shall be equal to the width of the 100 year water surface (for post-development conditions), including a minimum 1 foot of freeboard.
E. In sub-areas where individual stormwater management facilities would be provided for each development site, the individual stormwater management facilities shall be designed to ensure that the post-development peak discharge at the mouth of the sub-area does not exceed the arithmetic product of the applicable release rate, specified on Plat 4 of this Part and the predevelopment peak flow from the particular site under consideration.
F. For development sites that would be located in two or more sub-areas, the applicable release rates for the portions of the site located in different sub-areas shall be based on natural sub-area drainage boundaries. The natural drainage boundaries between sub-areas shall not be modified, nor shall drainage from a development site be diverted or otherwise conveyed from one sub-area to another sub-area, except where runoff naturally crosses sub-areas drainage boundaries.
G. No Harm Option.
(1) For any proposed development site not located in a provisional no detention sub-area, the developer has the option of using a less restrictive runoff control (including no detention) if the developer can prove that “no harm” would be caused by discharging at a higher runoff rate than that specified by the plan. 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 Hogestown Run/Trindle Spring Run with the Conodoguinet Creek. Proof of “no harm” must be shown using the capacity criteria specified in §103(3)(C) if downstream capacity analysis is a part of the “no harm” justification.
(2) Attempts to prove “no harm” based upon downstream peak flow versus capacity analysis shall be governed by the following provisions:
(a) The peak flow values to be used for downstream areas for the design return period storms (2, 10 and 25 year) shall be the values from the calibrated Hogestown Run/Trindle Spring Run watershed. These flow values would be supplied to the developer by the Township Engineer upon request.
(b) Any available capacity in the downstream conveyance system as documented by a developer may be used by the developer only in proportion to his development site acreage relative to the total upstream undeveloped acreage from the identified capacity (i.e., if the site is 10% of the upstream undeveloped acreage, the developer may use up to 10% of the documented downstream available capacity).
(c) Developer proposed construction generating increased peak flow rates at documented storm drainage problem areas would, by definition, be precluded from successful attempt to prove “no harm,” except in conjunction with proposed capacity improvements for the problem areas consistent with this Part.
(d) The developer must assume that the entire sub-area in which the site is located is developed in accordance with the zoning in effect at the project is to be approved for development.
(3) Any “no harm” justification shall be submitted by the developer as part of the drainage plan submission per §104.
H. Regional or Sub-Regional Stormwater Management Facilities. For certain areas within the watersheds, it may be cost‑effective to provide one stormwater management facility for an entire sub-area, group of sub-areas or portion of a sub-area incorporating more than one development site. The initiative and funding for any regional or sub-regional stormwater management alternatives are the responsibility of prospective developers and will be approved by the Township on a case‑by‑case basis. The design of any regional stormwater management facilities must assume development of the entire area that would drain to the regional facility. The type and amount of development that the developer(s) must consider shall be based on current Township Zoning [Chapter 27]. The peak outflow from a regional stormwater management facility must be consistent with the Hogestown Run/Trindle Spring Run watersheds, Act 167 “Stormwater Management Plan” using a model which is acceptable to the Township Engineer. When regional or sub-regional stormwater management facilities are utilized, the effect of phased growth on stormwater runoff flows must be considered. At no time from the initial phase through ultimate development shall the peak runoff flows exceed the predevelopment peak multiplied by the applicable release rate.
I. Capacity Improvements. If the developer can prove that it would be feasible to provide capacity improvements to relief the capacity deficiency in the existing drainage network, then adequate capacity improvements can be provided by the developer in lieu of stormwater management facilities on the development site. Any capacity improvements would be designed based on development of all areas tributary to the improvement and the capacity criteria specified in this Part. The type and amount of development that the developer must consider shall be based on current zoning and existing land uses. It shall be assumed that all new development upstream of a proposed capacity improvement would implement applicable stormwater management techniques, consistent with this Part.
J. Erosion protection shall be provided along all open channels and at all points of discharge. Design erosion protection in accordance with Erosion and Sediment Pollution Control Program Manual, as amended, published by the PA DEP. [Ord. 98-7]
K. Existing and proposed ponds and other similar open water features that are not designed as stormwater management facilities shall be designed in accordance with the United States Department of Agriculture, Soil Conservation Service (SCS), Ponds ‑ Planning, Design, Construction (as amended or replaced from time to time by SCS) and shall be treated as impervious surfaces for stormwater runoff computations.
L. The design of all stormwater management facilities shall incorporate sound engineering principles and practices. The Township Engineer shall reserve the right to disapprove any design that would result in the occurrence or perpetuation of an adverse hydrologic or hydraulic condition within the watershed.
4. Calculation Methodology.
A. Stormwater runoff calculations involving drainage areas greater than 20 acres, including on and off‑site areas, shall use any generally accepted calculation technique that is based on the SCS soil cover complex method. Use the rational method to estimate peak discharges from drainage areas that contain less than 20 acres.
B. Design stormwater detention facilities to meet the performance standards of this Part by routing the design storm hydrograph through these facilities using the storage‑indication method. For drainage areas greater than 20 acres in size, the design storm hydrograph shall be computed using a calculation method that produces a full hydrograph. For drainage areas containing less than 20 acres, calculate the full hydrograph using approximate techniques.
C. All calculations using the soil cover complex method shall use the Soil Conservation Service Type II 24 hour rainfall distribution. The 24 hour rainfall depths for the various return periods to be used with this Part are (taken from rainfall duration frequency tables for Pennsylvania, PA DEP) as follows: [Ord. 98-7]
|Return Period||24 Hour Rainfall Depth|
|2 Year||2.5 Inches|
|10 Year||3.7 Inches|
|25 Year||4.4 Inches|
|100 Year||5.3 Inches|
D. All calculations using the rational method shall use rainfall intensities consistent with appropriate times of concentration for overland flow and return periods published by PennDOT in Design Manual 2, as amended. Times of concentration for overland flow shall be calculated using the methodology presented in Chapter 3 of “Urban Hydrology for Small Watersheds,” SCS, TR‑55 (as amended or replaced from time to time SCS). Times of concentration for channel and pipe flow shall be computed using Manning’s equation.
E. Runoff curve numbers (CN) for both existing and proposed conditions to be used in the soil curve complex method shall be obtained from Table A‑1 in the Appendix of this Part.
F. Runoff coefficients (c) for both existing and proposed conditions for use in the rational method shall be obtained from either Table A‑2 or Figure A‑1 in the Appendix of this Part.
G. Where uniform flow is anticipated, the Manning equation shall be used for hydraulic computations and to determine the capacity of open channels, pipes and storm sewers. Where non-uniform flow is anticipated, the hydraulic effects of “backwater” caused by hydraulic obstructions (e.g. culverts, bridges, dams, reservoirs, etc.) shall be evaluated using the standard step method for determining water surface profiles. Values for Manning’s roughness coefficient (n) shall be consistent with Table A‑3 in the Appendix of this Part. Permissible velocities for channels shall be no more than the values indicated in Table A‑4 of the Appendix.
H. Outlet structures for stormwater management facilities shall be designed to meet the performance standards of this Part using any generally accepted hydraulic analysis technique or method.
(Ord. 95-9, 8/31/1995, Art. III; as amended by Ord. 98-7, 8/27/1998)
§104. DRAINAGE PLAN REQUIREMENTS.
1. General Requirements. For any of the activities regulated by this Part, the final approval of subdivision and/or land development plans, the issuance of any building or occupancy permit, or the commencement of any land disturbance activity may not proceed until the property owner or developer or his/her agent has received written approval of a drainage plan from the plan administrator.
A. Any regulated activity that would create 10,000 square feet or less of impervious area is exempt from the drainage plan preparation provisions of this Part. This criteria shall apply to the total development even if development is to take place in phases. Exemption shall not relieve the applicant from providing adequate stormwater management to meet the purpose of this Part.
B. Land disturbance associated with existing one and two family dwellings, subject to conditions described in subsection (2)(A) of this Section.
C. Use of land for gardening for home consumption.
D. Agriculture when operated in accordance with a conservation plan or erosion and sedimentation control plan prepared by the Conservation District. The agricultural activities such as growing crops, rotating crops, filling of soil and grazing animals and other such activities are specifically exempt from complying with the requirements of this Part when such activities are conducted in accordance with a conservation plan prepared by the Cumberland County Conservation District. The construction of buildings, parking lots or any activity that may result in impervious surface which increases the rate and volume of stormwater runoff shall comply with the requirements of this Part.
E. Forest management operations which are following the Department of Environmental Protection’s management practices contained in its publication “Soil Erosion and Sedimentation Control Guidelines for Forestry” and are operating under an erosion and sedimentation control plan. No exemption shall be provided for regulated activities as defined in §101(4)(F) of this Part. [Ord. 98-7]
3. Drainage Plan Contents. The drainage plan shall consist of all applicable calculations, maps and plans. A note on the maps shall refer to the associated computations and erosion and sedimentation control plan by title and date. The cover sheet of the computations and erosion and sedimentation control plan shall refer to the associated maps by title and date. All drainage plan materials shall be submitted to the plan administrator in a format that is clear, concise, legible, neat and well organized; otherwise, the drainage plan shall be disapproved and returned to the applicant. The following items shall be included in the drainage plan:
(1) General description of project.
(2) General description of permanent stormwater management techniques, including construction specifications of the materials to be used for stormwater management facilities.
(3) Complete hydrologic, hydraulic and structural computations for all stormwater management facilities.
B. Map(s) of the project area shall be submitted on 24 inch x 36 inch or 30 inch x 42 inch sheets and shall be prepared in a form that meets the requirements for recording the office of the Recorder of Deeds of Cumberland County. The contents of the map(s) shall include, but not be limited to:
(1) The location of the project relative to highways, municipalities or other identifiable landmarks.
(2) Existing contours at intervals of 2 feet. In areas of steep slopes (greater than 15%), 5 feet contour intervals may be used.
(3) Existing streams, lakes, ponds or other bodies of water within the project area.
(4) Other physical features including flood hazard boundaries, sinkholes, streams, existing drainage courses, areas of natural vegetation to be preserved, and the total extent of the upstream area draining through the site.
(5) The locations of all existing and proposed utilities, sanitary sewers and water lines within 50 feet of property lines.
(6) An overlay showing soil names and boundaries.
(7) Proposed changes to the land surface and vegetative cover, including the type and amount of impervious area that would be added.
(8) Proposed structures, roads, paved areas and buildings.
(9) Final contours at intervals of 2 feet. In areas of steep slopes (greater than 15%), 5 foot contour intervals may be used.
(10) The name of the development, the name and address of the owner of the property and the name of the individual or firm preparing the plan.
(11) The date of submission.
(12) A graphic and written scale of 1 inch equals no more than 50 feet for tracts of 20 acres or more, the scale shall be 1 inch equals no more than 100 feet.
(13) A North arrow.
(14) The total tract boundary an size with distances marked to the nearest foot and bearings to the nearest degree.
(15) Existing and proposed land use(s).
(16) A key map showing all existing manmade features beyond the property boundary that would be affected by the project.
(17) Horizontal and vertical profiles of all open channels, including hydraulic capacity.
(18) Overland drainage paths.
(19) A 20 feet wide access easement around all stormwater management facilities that would provide ingress from and egress to a public right‑ of‑way.
(20) A note on the plan indicating the location and responsibility for maintenance of stormwater management facilities that would be located off‑site. All off‑site facilities shall meet the performance standards and design criteria specified in this Part.
(21) A construction detail of any improvements made to sinkholes and the location of all notices to be posted, as specified in this Part.
(22) A statement, signed by the landowner, acknowledging the stormwater management system to be a permanent fixture that can be altered or removed only after approval of a revised plan by the plan administrator.
(23) The following signature block for the plan administrator:
“I, (plan administrator), on this date (date of signature), have reviewed and hereby certify that the drainage plan meets all design standards and criteria of the Stormwater Management Ordinance.”
(24) The location of all erosion and sedimentation control facilities.
C. Supplemental Information.
(1) A written description of the following information shall be submitted:
(a) The overall stormwater management concept for the project.
(b) Stormwater runoff computations as specified in this Part.
(c) Stormwater management techniques to be applied both during and after development.
(d) Expected project time schedule.
(2) A soil erosion and sedimentation control plan, including all reviews and approvals, as required by PA DEP. [Ord. 98-7]
(3) A geologic assessment of the effects of runoff on sinkholes as specified in this Part.
(4) The effect of the project (in terms of runoff volumes and peak flows) on adjacent properties and on any existing Township stormwater collection system that may receive runoff from the project site.
(5) A declaration of adequacy and highway occupancy permit from the PennDOT District Office when utilization of a PennDOT storm drainage system is proposed.
D. Stormwater Management Facilities.
(1) All stormwater management facilities must be located on a map and described in detail.
(2) When groundwater recharge methods such as seepage pits, beds or trenches are used, the locations of existing and proposed septic tank infiltration areas and wells must be shown.
(3) All calculations, assumptions and criteria used in the design of the stormwater management facilities must be shown.
4. Plan Submission. For all activities regulated by this Part, the steps below shall be followed for submission. For any activities that require a PA DEP Joint Permit Application and are regulated under Chapter 105 (Dam Safety and Waterway Management) or Chapter 106 (Floodplain Management) of PA DEP’s Rules and Regulations, require a PennDOT highway occupancy permit or require any other permit under applicable State or Federal regulations, the permit(s) shall be part of the plan. [Ord. 98-7]
A. The drainage plan shall be submitted by the developer as part of the preliminary plan submission for the regulated activity.
B. Four copies of the drainage plan shall be submitted.
C. Distribution of the drainage plan will be as follows:
(1) One copy to the Township accompanied by the requisite Township review fee, as specified in this Part.
(2) One copy to the Township Engineers.
(3) Two copies to the plan administrator accompanied by the requisite plan administrator review fee as specified in this Part.
5. Drainage Plan Review.
A. The plan administrator shall review the drainage plan. The plan administrator shall require receipt of a complete plan, as specified in this Part.
B. The Township Engineer shall review the drainage plan for any subdivision or land development against the Township Subdivision and Land Development Ordinance [Chapter 22] provisions not superseded by this Part.
C. For activities regulated by this Part, the plan administrator shall notify the Township in writing, within 90 calendar days, whether the drainage plan is consistent with this Part. Should the drainage plan be determined to be consistent with this Part, the plan administrator will forward an approval letter to the Township Secretary with a copy to the developer. Should the drainage plan be determined to be inconsistent with this Part, the plan administrator will forward a disapproval letter to the Township Secretary and developer citing the reason(s) for the disapproval. Any disapproved drainage plans may be revised by the developer and resubmitted consistent with this Part.
D. For regulated activities specified in §101(4)(C) and (D) of this Part, the plan administrator shall notify the Township Building Permit Officer in writing, within a time frame consistent with the Township Building Code, whether the drainage plan is consistent with this Part and forward a copy of the approval/disapproval letter to the developer. Any disapproved drainage plan may be revised by the developer and resubmitted consistent with this Part.
E. For regulated activities requiring a PA DEP joint permit application, the plan administrator shall notify PA DEP whether the drainage plan is consistent with this Part and forward a copy of the review letter to the Township and the developer. PA DEP may consider the plan administrator’s review comments in determining whether to issue a permit. [Ord. 98-7]
F. The Township shall not approve any subdivision or land development for regulated activities specified in §101(4)(A) and (B) of this Part if the drainage plan has been found to be inconsistent with this Part, as determined by the plan administrator, or without considering the comments of the Township Engineer. All required permits from PA DEP must be obtained prior to approval. [Ord 98-7]
G. The Township Building Permit Office shall not issue a building permit for any regulated activity specified in §101(4)(C) and (D) of this Part if the drainage plan has been found to be inconsistent with this Part, as determined by the plan administrator, or without considering the comments of the Township Engineer. All required permits from PA DEP must be obtained prior to issuance of a building permit. [Ord. 98-7]
H. The developer shall be responsible for completing an “as‑built survey” of all stormwater management facilities included in the approved drainage plan. The as‑built survey and an explanation of any discrepancies with the design plans shall be submitted to the plan administrator for final approval. In no case shall the plan administrator approve the as‑built survey until the plan administrator receives a copy of an approved declaration of adequacy, highway occupancy permit from the PennDOT District Office, and any applicable permits from PA DEP. [Ord. 98-7]
I. The plan administrator’s approval of a drainage plan shall be valid for a period not to exceed 1 year. This 1 year time period shall commence on the date that the plan administrator signs the approved drainage plan. If stormwater management facilities included in the approved drainage plan have not been constructed, or if an as‑built survey of these facilities has not been approved within this 1 year time period, then the plan administrator may consider the drainage plan disapproved and may recommend that the Township revoke any and all permits. Drainage plans that are considered disapproved by the plan administrator shall be resubmitted in accordance with §104(7) of this Part.
6. Modification of Plans .
A. A modification to a submitted drainage plan for a development site that involves a change in stormwater management facilities or techniques, or that involves the relocation or redesign of stormwater management facilities, or that is necessary because soil or other conditions are not as stated on the drainage plan (as determined by the plan administrator or the Township Engineer), shall require a resubmission of the modified drainage plan consistent with §104(4) of this Part and be subject to review as specified in §104(5) of this Part.
B. A modification to an already approved or disapproved drainage plan shall be submitted to the plan administrator, accompanied by the applicable plan administrator review fee. A modification to a drainage plan for which a formal action has not been taken by the plan administrator shall be submitted to the plan administrator, accompanied by the applicable plan administrator review fee.
7. Resubmission of Disapproved Drainage Plans. A disapproved drainage plan may be resubmitted, with the revisions addressing the plan administrator’s concerns documented in writing, to the plan administrator in accordance with §104(4) of this Part and be subject to review as specified in §104(5) of this Part. The applicable plan administrator review fee must accompany a resubmission of a disapproved drainage plan.
(Ord. 95-9, 8/31/1995, Art. IV; as amended by Ord. 98-7, 8/27/1998)
§105. SCHEDULE OF INSPECTIONS.
1. The plan administrator or his assignee shall inspect all phases of the installation of the permanent stormwater management facilities.
2. During any stage of the work, if the plan administrator determines that the permanent stormwater management facilities are not being installed in accordance with the approved plans, the Township shall revoke any existing permits until a revised drainage plan is submitted and approved, as specified in this Part.
(Ord. 95-9, 8/31/1995, Art. V)
§106. FEES AND EXPENSES.
1. General. The fees required by this Part are the Township review fee and the plan administrator review fee. The Township review fee shall be established by the Township to defray review costs incurred by the Township and the Township Engineer. The plan administrator review fee shall be established by the plan administrator to defray the plan administrator’s review costs. All fees shall be paid by the applicant.
2. Plan Administrator Drainage Plan Review Fee. The plan administrator shall establish a review fee schedule based on the size of the regulated activity and based on the plan administrator’s costs for reviewing drainage plans. The plan administrator shall periodically update the review fee schedule to ensure that review costs are adequately reimbursed.
3. Expenses Covered by Fees. The fees required by this Part shall at a minimum cover:
A. The review of the drainage plan by the plan administrator and the Township Engineer.
B. The site inspection.
C. The inspection of stormwater management facilities and drainage improvements during construction.
D. The final inspection upon completion of the stormwater management facilities an drainage improvements presented in the drainage plan.
E. Any additional work required to enforce any permit provisions regulated by this Part, correct violations and assure proper completion of stipulated remedial actions.
(Ord. 95-9, 8/31/1995, Art. VI)
§107. MAINTENANCE RESPONSIBILITIES.
1. Maintenance Responsibilities.
A. The stormwater management plan for the development site shall contain an operation and maintenance plan prepared by the developer and approved by the Township Engineer. The operation and maintenance plan shall outline required routine maintenance actions and schedules necessary to insure proper operation of the facility(ies).
B. The stormwater management plan for the development site shall establish responsibilities for the continuing operating and maintenance of all proposed stormwater control facilities, consistent with the following principals:
(1) If a development consists of structures or lots which are to be separately owned and in which streets, sewers and other public improvements are to be dedicated to the Township, stormwater control facilities should also be dedicated to and maintained by the Township.
(2) If a development site is to be maintained in a single ownership or if sewers and other public improvements are to be privately owned and maintained, then the ownership and maintenance of stormwater control facilities should be the responsibility of the owner or private management entity.
C. The Board of Commissioners, upon recommendation of the Township Engineer, shall make the final determination on the continuing maintenance responsibilities prior to final approval of the stormwater management plan. The Board of Commissioners reserves the right to accept the ownership and operating responsibility for any or all of the stormwater management controls.
2. Maintenance Agreement for Stormwater Facilities Dedicated to the Township. Any stormwater facility dedicated to the Township shall comply with the provisions of §107(4)(A), (2) and (3) and §107(4)(B) and (C).
3. Maintenance Agreement for Privately Owned Stormwater Facilities.
A. Prior to final approval of the site’s stormwater management plan, the property owner shall sign and record a maintenance agreement covering all stormwater control facilities which are to be privately owned. The agreement shall stipulate that:
(1) The owner shall maintain all facilities in accordance with the approved maintenance schedule and shall keep all facilities in a safe and attractive manner.
(2) The owner shall convey to the Township easements and/or rights‑of‑way to assure access for periodic inspections by the Township and maintenance, if required.
(3) The owner shall keep on file with the Township the name, address and telephone number of the person or company responsible for maintenance activities; in the event of a change, new information will be submitted to the Township within 10 days of the change.
(4) If the owner fails to maintain the stormwater control facilities following due notice by the Township to correct the problem(s), the Township may perform the necessary maintenance work or corrective work and the owner shall reimburse the Township for all costs.
B. Other items may be included in the agreement where determined necessary to guarantee the satisfactory maintenance of all facilities. The maintenance agreement shall be subject to the review and approval of the Township Solicitor and Board of Commissioners.
4. Township Stormwater Maintenance Fund.
A. Persons installing stormwater storage facilities shall be required to pay a specified amount to the Township stormwater maintenance fund to help defray costs of periodic inspections and maintenance expenses. The amount of the deposit shall be determined as follows:
(1) If the storage facility is to be privately owned and maintained, the deposit shall cover the cost of periodic inspections performed by the Township for a period of 10 years, as estimated by the Township Engineer. After that period of time, inspections will be performed at the expense of the Township.
(2) If the storage facility is to be owned and maintained by the Township, the deposit shall cover the estimated costs for maintenance and inspections for 10 years. The Township Engineer will establish the estimated costs utilizing information submitted by the applicant.
(3) The amount of the deposit to the fund shall be converted to present worth of the annual series values. The Township Engineer shall determine the present worth equivalents which shall be subject to the approval of the Board of Commissioners.
B. If a storage facility is proposed that also serves as a recreation facility (e.g., ball field, lake), the Township may reduce or waive the amount of the maintenance fund deposit based upon the value of the land for public recreation purposes.
C. If at some future time a storage facility (whether publicly or privately owned) is eliminated due to the installation of storm sewers or other storage facility, the unused portion of the maintenance fund deposit will be applied to the cost of abandoning the facility and connecting to the storm sewer system or other facility. Any amount of the deposit remaining after the costs of abandonment are paid will be returned to the depositor.
(Ord. 95-9, 8/31/1995, Art. VII)
§108. ENFORCEMENT AND PENALTIES.
1. Right‑of‑Entry. Upon presentation of proper credentials, duly authorized representatives of the Township may enter at reasonable times upon any property within the Township to investigate or ascertain the condition of the subject property in regard to any aspect regulated by this Part.
2. Notification. In the event that a person fails to comply with the requirements of this Part, or fails to conform to the requirements of any permit issued hereunder, the Township shall provide written notification of the violation. Such notification shall set forth the nature of the violation(s) and establish a time limit for correction of these violation(s). Failure to comply within the time specified shall subject such person to the penalty provisions of this Part. All such penalties shall be deemed cumulative and resort by the Township from pursuing any and all other remedies. It shall be the responsibility of the owner of the real property on which any regulated activity is proposed to occur, is occurring, or has occurred, to comply with the terms and conditions of this Part.
A. Any person who or which has violated any provision of this Part shall, upon judicial determination thereof, be subject to civil judgment for each such violation of not more than $1,000 plus costs of suit. Each day that a violation occurs shall constitute a separate offense. All fines shall be paid to the Township of Hampden for its use.
B. In addition, the Township of Hampden may institute injunctive, mandamus or any other appropriate action or proceeding at law or in equity for the enforcement of this Part. Any court of competent jurisdiction shall have the right to issue restraining orders, temporary or permanent injunctions, mandamus or other appropriate forms of remedy or relief.
A. Any person aggrieved by any action of the Township or its designee may appeal to Township’s Board of Commissioners within 30 days of that action.
B. Any person aggrieved by any decision of the Hampden Township Board of Commissioners may appeal to the Court of Common Pleas of Cumberland County within 30 days of that decision.
(Ord. 95-9, 8/31/1995, Art. VIII; as amended by Ord. 98-7, 8/27/1998)
1. Compatibility with Other Ordinance Requirements. Approvals issued pursuant to this Part do not relieve the applicant of the responsibility to secure required permits or approvals for activities regulated by any other applicable Federal, State or local code, rule, act or ordinance.
2. Township Liability. The making of an administrative decision shall not constitute a representation, guarantee or warranty of any kind by the Township of Hampden as to the safety of any proposed structure or use with respect to damage from erosion, sedimentation, stormwater runoff or floods, and shall create no liability upon, or cause of action against said Township of Hampden or its officials, employees or agents.
(Ord. 95-9, 8/31/1995, Art. IX)