All storm water management, collection, conveyance, erosion control, and floodplain considerations shall be accomplished in accordance with the following provisions:

Section 610.1  General Requirements 

Prior to the final approval of any subdivision or land development plan, or the commencement of any development within the jurisdiction of this Ordinance, the developer shall submit a Storm Water Management Plan to the Township for approval.

A.                 When plan applications, whether preliminary or final, are submitted in sections, a generalized Storm Water Management Plan for the entire project site shall be submitted in addition to the detailed Storm Water Management Plan for the proposed section.  This generalized plan shall demonstrate how the storm water of the proposed section will relate to the entire development. The amount and velocity at the discharge point of the section shall be included in the data submitted. If temporary facilities are required for construction of a section, such facilities shall be included in the submitted plans.

B.                 The type, location and extent of all erosion and sedimentation control measures shall be shown on an erosion and sedimentation control plan that conforms to the requirements of the Soil Erosion and Sedimentation Control Manual of the Pennsylvania Department of Environmental Protection and the Design Standards of Section 610.6 of this Ordinance.

C.                 A written report shall be submitted that includes the following  information:

1.                  Storm water runoff calculations for both pre-development and post- development conditions.

2.                  An erosion and sedimentation control plan narrative that conforms to the requirements of the Soil Erosion and Sedimentation Control Manual of the Pennsylvania Department of Environmental Protection and provides a description of all erosion and sedimentation control measures, temporary as well as permanent, including the staging of earth moving activities, sufficient in detail to clearly indicate their function.

3.                  An ownership and maintenance program, in recordable form, that clearly sets forth the ownership and maintenance responsibility of all temporary and permanent storm water management facilities and erosion and sedimentation control facilities, including:

a.                   Description of temporary and permanent maintenance requirements;

b.                  Identification of a responsible individual, corporation, association or other entity for ownership and maintenance of both temporary and permanent storm water management and erosion and sedimentation control facilities;

c.                   Establishment of suitable easements for access to all facilities;

d.                  The intent of these regulations is to provide private ownership and maintenance of storm water management and erosion and sedimentation control facilities. Where the Board of Supervisors accepts dedication of storm water management facilities, the Board of Supervisors may require the developer to establish, at the time of dedication, a maintenance fund, in an amount determined by the Township, adequate for the perpetual care of such facilities, including detention basins;

e.                   For all proposed detention basins and retention basins, except temporary sedimentation basins, the documentation shall include a plotting or tabulations of storage volumes with corresponding water surface elevations and the outflow rates for those water surfaces; and,

f.                   For all proposed detention basins and retention basins, except temporary sediment basins, documentation shall set forth the design hydrograph, the shortcut routing method or a method of equal caliber acceptable to the Township Engineer, utilized to determine the function of the basin.

Section 610.2  Design Standards

A.                 Where applicable, storm water management facilities shall comply with the requirements of Chapter 105 (Water Obstructions and Encroachments) of Title 25, Rules and Regulations, as amended, of the Pennsylvania Department of Environmental Protection.

B.                 Storm water management facilities that involve a State Highway shall also be subject to the approval of the Pennsylvania Department of Transportation.

C.                 Storm water management facilities located within or affecting the floodplain of any watercourse shall comply with the requirements of the flood plain regulations provided in the Zoning Ordinance or any future ordinances regulating construction or development within areas of the Township subject to flooding.

D.                 Storm water discharge points onto an adjacent property shall comply with the following:

1.                  Storm water runoff from a project site shall flow directly into a natural watercourse or into an existing storm sewer system. If neither of these is available, the applicant shall obtain an easement from the downstream landowner(s) to allow the site’s runoff discharge to reach a natural watercourse or an existing storm sewer system through the easement.  If an easement is obtained, post-developed flow characteristics must be similar to or better than the runoff characteristics (spread, velocity, and peak rate) of the pre-developed flows.  The easement from the downstream property owner(s) shall be to allow for a piped storm sewer system, an overland flow system, or a combination of the two.  The downstream system design shall conform to the design requirements of this ordinance.

2.                  When the applicant provides verification that the downstream landowner(s) refuses to grant an easement, the site shall be designed such that the discharge from the applicant’s site shall be in a non-erosive, sheet flow condition.  For all design year storms, including the 100-year storm, runoff from the applicant’s site shall flow onto the adjacent property in a manner similar to the runoff characteristics (spread, velocity, and peak rate) of the pre-developed flow.  The use of level spreaders is discouraged.

3.                  Storm water runoff shall not be transferred from one watershed to another unless the watersheds are sub-watersheds of a common watershed which join together within the perimeter of the property, or both of the following apply: 1) the effect of the transfer does not alter the peak discharge onto adjacent lands, and, 2) drainage easements from the affected landowners are provided.

E.                  Unless an alternate design is submitted to the Township for review, and said design is prepared by a licensed (in the Commonwealth of Pennsylvania) geologist or geotechnical engineer:

1.                  No storm water facilities shall be placed in, over or immediately adjacent to the following features:

a.                   Sinkholes

b.                  Closed depressions

c.                   Lineaments in carbonate areas

d.                  Fracture traces

e.                   Caverns

f.                   Intermittent Streams

g.                   Ephemeral streams

h.                  Bedrock pinnacles (surface or subsurface)

2.                  The minimum isolation distance from storm water management basins to the listed geologic features shall be as follows:

a.                   One hundred (100) feet from the rim of sinkholes or closed depressions;

b.                  One hundred (100) feet from disappearing streams;

c.                   Fifty (50) feet from lineaments or fracture traces;

d.                  Twenty-five (25) feet from surface or identified subsurface pinnacles.

3.                  Storm water runoff from any subdivision or land development activities shall not be discharged into sinkholes.

F.                  All storm water runoff flowing over the project site shall be considered in the design of the storm water management facilities.

G.                 The calculated peak rates of runoff for storm water originating on the project site must meet the following conditions, for all watersheds flowing from the project site:

1.                  Post-development runoff from any regulated activity shall not exceed the peak rates of runoff prior to development for all design storms (2, 5, 10, 25, 50, and 100 year storm events.

H.                 Innovative methods for the detention and control of storm water runoff may be used when approved by the Township. Various combinations of methods should be tailored to suit the particular requirements of the type of development and the topographic features of the project site.  The following is a partial listing of detention and control methods which can be utilized in storm water management systems where appropriate:

1.                  Detention basins and retention basins;

2.                  Roof-top storage;

3.                  Parking lot ponding;

4.                  Seepage pits, seepage trenches or other infiltration structures;

5.                  Concrete lattice block surfaces;

6.                  Grassed channels and vegetated strips;

7.                  Cisterns and underground reservoirs;

8.                  Routed flow over grass; and,

9.                  Decreased impervious surface coverage.

Section 610.3  Methods of Calculation of Runoff

A.                 The methods of computation used to determine peak discharge and runoff shall be:

1.                  The Soil-Cover-Complex Method (as set forth in the latest edition of Urban Hydrology for Small Watersheds, Technical Release No. 55 as published by SCS) shall be used for all detention facilities with a drainage area greater than or equal to sixty (60) acres.

2.                  The Rational Method shall be used for all:

a.                   Collection Facilities;

b.                  Conveyance Facilities;

c.                   Detention Facilities with drainage areas less than sixty (60) acres.

3.                  Any other method approved by the Township Engineer.

4.                  If the Soil-Cover-Complex (SCS) Method is used, storm water runoff shall be based on the following 24-hour storm events:

                                                Storm Event (years)     Inches of Rainfall

5.                  If the SCS Method is used, an antecedent moisture content of 1 shall be used for the pre-development condition.

6.                  If the Rational Method is used, the Rainfall Intensity–Duration–Frequency Chart shown in the Appendix shall be used to compute the rainfall intensity in inches per hour.

7.                  Runoff Coefficients “C” and Curve Numbers “CN” shall be based on the charts contained in the Appendix.

8.                  For the purpose of calculating peak discharges, all agricultural lands that contribute storm drainage to or from the project site shall be considered cultivated lands with conservation measures in good hydrologic condition.

9.                  Design of on-site conveyance systems calculations may use the Rational Method of Q=CIA where Q is the peak discharge of the watershed in cubic feet per second, C is the coefficient of runoff, I is the intensity of rainfall in inches per hour, and A is the area of the watershed in acres; or any other method approved by the Township.

10.              Runoff calculations shall include a hydrologic and hydraulic analysis indicating volume and velocities of flow and the grades, sizes, and capacities of water carrying structures, sediment basins, retention and detention structures and sufficient design information to construct such facilities.  Runoff calculations shall also indicate both pre-development and post-development rates for peak discharge of storm water runoff from the project site.

11.              Flow calculations for water carrying structures shall be presented in tabular form using the flow tabulation form provided in the Appendix (or equal).

12.              Permanent detention basins shall be designed with a primary outlet discharge that is less than or equal to the requirements for post-development peak rate of runoff established by Section 610.2.f of this Ordinance.

13.              Runoff calculations will also be made to insure that the runoff from the upstream watershed area can be accommodated by the pipes, drainage easements, watercourses, etc. on the site.

Section 610.4                Design Standards – Water Carrying Facilities

A.                 All storm sewer pipes, grass waterways, open channels, swales and other water carrying facilities that service drainage areas within the site shall be designed to convey the twenty-five (25) year storm event unless in the opinion of the Township or Township Engineer the character of development and potential for damage warrant design for the 50 or 100 year storm.

B.                 Storm water management facilities that convey off-site water through the site shall be designed to convey the fifty (50) year storm event.

C.                 All developments shall include provisions that allow for the overland conveyance and flow of the post-developed one hundred (100) year storm event without damage to public or private property.

D.                 All storm sewer pipes, culverts, manholes, inlets, endwalls and endsections shall be constructed in accordance with Pennsylvania Department of Transportation, Form 408, as amended.

E.                  Storm sewer pipes, culverts, manholes, inlets, endwalls, and endsections proposed for dedication or located along streets shall conform to the requirements of the Pennsylvania Department of Transportation, Bureau of Design, Standards for Roadway Construction, Publication No. 72, in effect at the time the design is submitted, as modified by the Township.

F.                  Storm sewer pipes and culverts shall be reinforced concrete pipe (RCP) or  smooth  lined  corrugate  polyethylene  (SLCPP), shall have a minimum diameter of eighteen (18) inches, and shall be installed on a sufficient slope to provide a minimum velocity of three (3) feet per second when flowing full.

G.                 All storm sewer pipe shall be laid to a minimum depth of one (1) foot from subgrade to the crown of pipe.

H.                 Endwalls and endsections shall be used where storm water runoff enters or leaves the storm sewer horizontally from a natural or manmade channel.

I.                    Inlets shall be placed on both sides of the street at low spots, at a maximum of six hundred (600) feet apart along a storm sewer pipe, at points of abrupt changes in the horizontal or vertical directions of storm sewers, and at points where the flow in gutters exceeds three (3) inches. Inlets shall normally be along the curb line at or beyond the curb radius points.  For the purpose of inlet location at corners, the depth of flow shall be considered for each gutter. At intersections, the depth of flow across the through streets shall not exceed one (1) inch.  Inlets shall be depressed two (2) inches below the grade of the road-side swale, curb line, or ground surface. Manholes may be substituted for inlets at locations where inlets are not required to collect surface runoff.

J.                   Storm water roof drains and pipes, wherever possible shall discharge water into a storm water runoff dispersion or infiltration control device and not into storm sewers or street gutters.

K.                 All existing and natural watercourses, channels, drainage systems and areas of surface water concentration shall be maintained in their existing condition unless an alteration is approved by the Township.

L.                  Flow velocities from any storm sewer shall not result in a degradation of the receiving channel.

M.                Energy dissipaters shall be placed at the outlets of all storm sewer pipes where flow velocities exceed maximum permitted channel velocities.

N.                 The capacities of grassed waterways shall be computed from the Manning Equation.  Permissible open channel velocities and design standards shall be in accordance with good engineering practice as documented in the Engineering Field Manual for Conservation Practices, U.S.D.A., S.C.S., or in Design Charts for Open-Channel Flow, Hydraulic Design Series No. 3, U.S. Department of Transportation.

O.                 Grassed waterways may be utilized in place of conduit piping in those areas where soil conditions allow recharge of groundwater.  All newly installed grassed waterways must be well-established sod of good quality or matted with an approved stabilizing material.  The usage of grassed waterways is not recommended in areas of year round or seasonally high ground water table unless provisions are made to handle long duration flows, for example by means of subsurface drainage of stone centered waterways.

1.                  The shape of the waterway shall permit hydraulic efficiency and ease of maintenance. Allowable velocities within the waterway shall be limited to those values that would not cause erosion of the soil or cover material.  Vegetation or durable materials shall be established on all channels where design velocities exceed the maximum values for base earth channels.  Permanent channels should be designed using grass or other suitable material.

2.                  The following information should be utilized in selecting adequately sized channels that do not exceed maximum velocities.  The maximum permissible velocity shall be selected as the lowest value from Sections 610.4.O.a and 610.4.O.b which follow:

a.                   Guidelines for maximum permissible velocities relevant to individual site conditions:

1).                3.0 feet per second where only sparse vegetation can be established and maintained because of shade or soil conditions.

2).                3.0 - 4.0 feet per second should be used under normal conditions where the vegetation is to be established by seeding.

3).                4.0 - 5.0 feet per second should be used only in areas where a dense vigorous sod is obtained quickly or where water can be diverted out of the waterway during establishment of vegetation.  (Use where netting and mulch or other special methods of establishing vegetation are used).

4).                5.0 - 6.0 feet per second may be used on well-established sod of good quality (use where establishment of vegetation is by sodding or water is introduced to a previously sodded channel).

b.                  Soil characteristics, design velocities and the level of desired maintenance should be considered in determining seed mixtures and methods of establishment of vegetation.  Soils information for various soil types is contained in the "Lancaster County Soil Survey."  Maximum permissible velocities in feet per second based on vegetation, slope of waterway and soil erodibility are as follows:

c.                   Velocities for other channels are as follows:

                                                                                                            Maximum Permissible

                                    Channel Lining                                                            Velocity (feet/second)

                                    6" rip-rap                                                                                 4

                                    9" rip-rap                                                                                 8

                                    Durable Bedrock                                                                     8

                                    Asphalt                                                                                                7

                                    12" rip-rap                                                                               9

                                    Concrete or steel                                                                      12

Section 610.5  Design Standards – Detention and Retention Basins

A.                 All basins shall be structurally sound and shall be constructed of sound and durable materials.  The completed structure and the foundation of all basins shall be stable under all probable conditions of operation and shall be capable of discharging the peak discharge of a post-development 100-year storm event through the emergency spillway facilities, in a condition that assumes the primary outlet(s) are blocked, which will not damage the integrity of the facility or the downstream drainage areas.

B.                 The effect on downstream areas if the basin embankment fails shall be considered in the design of all basins.  Where possible, the basin shall be designed to minimize the potential damage caused by such failure of the embankment.

C.                 All detention basins shall include an outlet structure to permit draining the basin to a completely dry position within twenty-four (24) hours.

D.                 All outlet structures and emergency spillways shall include a satisfactory means of dissipating the energy of flow at its outlet to assure conveyance of flow without endangering the safety and integrity of the basin and the downstream drainage area.

E.                  A cutoff trench of relatively impervious clay material shall be provided within all basin embankments, except for those embankments with side slope ratios of three (3) horizontal to one (1) vertical or flatter.  Embankments with flatter side slopes shall have a key trench.

F.                  All culverts through basin embankments shall have properly spaced concrete cutoff collars or welded anti-seep collars.

G.                 A minimum one (1) foot freeboard above the design elevation of the water surface at the emergency spillway shall be provided.

H.                 No outlet structure from a detention basin or swale shall discharge directly onto any publicly used Township, state or private road but shall discharge into a culvert under or along the road.

I.                    The minimum top width of dams up to ten (10) feet in height shall be equal to two-thirds (2/3) of the dam height, but in no case shall the top width be less than five (5) feet.

Section 610.6  Design Standards - Erosion And Sediment Control

A.                 All earthmoving activities shall be conducted in such a way as to minimize accelerated erosion and resulting sedimentation.  Measures to control erosion and sedimentation shall, at a minimum, meet the standards of the Lancaster County Conservation District and Chapter 102 (Erosion Control) of Title 25, Rules and Regulations of the Pennsylvania Department of Environmental Protection.

B.                 The Erosion and Sedimentation Control Plan shall be submitted to the Lancaster County Conservation District for its review and approval.

C.                 Approval of an Erosion and Sedimentation Control Plan by the Township shall not be construed as an indication that the plan complies with the standards of any agency of the Commonwealth.

D.                 The following principles shall be applied to the design plan and construction schedule to minimize soil erosion and sedimentation.

1.                  Stripping of vegetation, grading or other soil disturbance shall be done in a manner that will minimize soil erosion.

2.                  Whenever feasible, natural vegetation shall be retained and protected.

3.                  The extent of the disturbed area and the duration of its exposure shall be kept to a  minimum, within practical limits.

4.                  Either temporary seeding, mulching or other suitable stabilization measures shall be used to protect exposed critical areas during construction.

5.                  Drainage provisions shall accommodate the storm water runoff both during and after construction.

6.                  Soil erosion and sedimentation facilities shall be installed prior to any on-site grading.

Section 610.7  Maintenance Of Storm Water Management Facilities

A.                 Maintenance is an essential part of the successful functioning of a storm water management system.

B.                 Maintenance during development of a project shall be the responsibility of the developer and/or landowner and shall usually include but not be limited to:

1.                  Removal of silt from all debris basins, traps or other structures or measures when 60% of capacity is filled with silt;

2.                  Periodic maintenance of temporary control facilities such as replacement of straw bale dikes, straw filters or similar measures;

3.                  Establishment or reestablishment of vegetation by seeding and mulching or sodding of scoured areas or areas where vegetation has not successfully been established;

4.                  Installation of necessary controls to correct unforeseen problems caused by storm events within design frequencies; and,

5.                  The contractor or developer shall be responsible for removal of all temporary measures and installation of permanent measures upon completion of the project.

C.                 Maintenance of the project after physical completion:

1.                  The applicant or his agent shall demonstrate that any facilities intended to be installed and located on an individual or group of individual lots can be adequately maintained by the homeowner(s) and/or lot owner(s).

2.                  It is the purpose of this Ordinance that Rapho Township shall not become responsible for maintenance and supervision of developed areas.  Such responsibility falls upon the party responsible for land development who shall remain personally responsible for those areas of the development which are subject to the require­ments of this Ordinance.  This responsibility may be retained or assigned to third persons as is deemed most acceptable to the party responsible for land development.  In the event that any portion of land development would, but for the existence of areas requiring maintenance subject to this Ordinance, be dedicated to the Municipality, the contractor or developer may make application to the Municipality for acceptance by the Municipality of such portions of the land development.  In the event that the Municipality, by formal action, accepts such portions of land development, maintenance and responsibility for such portions shall fall upon the Municipality.

3.                  It is the intent of this Ordinance that the purposes of the Ordinance shall be carried out through the exercise of responsibility by private parties, and, therefore, it is anticipated that control plans shall be developed with the view towards projects which can effectively be contained within the tracts to be owned and maintained by private parties.  To foster this purpose, with respect to portions or parts of a project as shown on a plan of a developer or contractor, which portions will not otherwise become part of municipal property, such portions shall become the responsibility of the individual property owners on whose property such portions of a project lie including but not limited to retention ponds, detention ponds, sediment basins, energy dissipaters or grassed water-ways.  Persons including contractors and developers conveying property of a development to another party, which property contains any portions of a Storm Water Management Plan, after that plan has been established, shall include a specific deed reference to such grantee's responsibility for the maintenance and care of the portions of such project as are included within said grantee's conveyed property.  The deed reference to such portions shall be in the form of a deed restriction imposing responsibilities upon said property owner for the maintenance of the portions of the project within the boundary lines of said property as may be necessary for proper maintenance of the project in accordance with the terms of this Ordinance.  Such maintenance shall include the following:

a.                   Liming and fertilizing vegetated channels and other areas according to specifications in the DEP "Erosion and Sediment Pollution Control Program Manual."

b.                  Reestablishment of vegetation by seeding and mulching or sodding of scoured areas or areas where vegetation has not been successfully established.

c.                   Mowing as necessary to maintain adequate strands of grass and to control weeds.  Chemical weed control may be used if state and local regulations are met.  Selection of seed mixtures shall be acceptable to the Township.

d.                  Removal of silt from all permanent structures which trap silt or sediment in order to keep the material from building up in grass waterways and thus reducing their capacity.

e.                   Repair of structural damage or deterioration of any kind, including the repair and maintenance of sinkholes and/or similar failures whether naturally occurring or created by human action.

f.                   Regular inspection of the areas in questions to assure proper maintenance and care.

4.                  The deed restrictions hereinabove mentioned shall also include notice that in the event the individual property owners should fail to comply with the terms of this Ordinance for the maintenance and care of the land in question, the Township of Rapho shall have the authority to carry out those duties hereby imposed upon individual property owners.  The Municipality may, after giving notice to an individual property owner that he is not properly maintaining the areas subject to this Ordinance, and by making demand that such compliance shall be made within thirty (30) days, enter upon said private property and take such actions as may be required to bring the area into compliance with this Ordinance.  The property owner shall be responsible for reimbursing the Township for any and all costs incurred by the Township in its actions required to bring the area into compliance with this Ordinance.  Should the property owner fail to reimburse the Township, the Township shall further have the right to file a municipal lien against such property for the cost of maintenance work carried out under this section.  The Municipality shall in addition to the filing of a municipal lien have any other remedies provided by law against any property owner who should fail to comply with the terms of this Ordinance.

5.                  Where the Township accepts dedication of all or some of the required storm water management facilities following completion, the Township may require the posting of financial security to secure structural integrity of said facilities as well as the functioning of said facilities in accordance with the design and specifications as depicted on the approved storm water management plan for a term not to exceed eighteen (18) months from the date of acceptance of dedication.  Said financial security shall be the same type as required with regard to installation of such facilities, and the amount of the financial security shall not exceed fifteen (15%) percent of the actual cost of installation of said facilities.

Section 610.8  Ownership And Maintenance

A.                 Prior to granting of final approval by the Municipality of a plan the applicant shall either (1) satisfactorily establish that the permanent facilities are part of a portion of ground to be dedicated to the Municipality for reasons other than the maintenance of land subject to this Ordinance, or (2) present to the Municipality a copy of restrictions with an affidavit stating that such restrictions shall be added to the deed of conveyance to each grantee to whom property of the development is to be conveyed.

B.                 When permanent Storm Water Management Facilities and ownership to these facilities are dedicated to and accepted by the Municipality, it shall be the Municipality's responsibility to maintain these facilities.

C.                 The Municipality shall have the right in addition to those provisions above set forth, to require the applicant, owner or developer to post a bond with the Municipality prior to the time of approval of the plan in order to assure the faithful performance of the requirements of this Ordinance in the course of completing the land development.

Section 610.9  Modification Of Facilities 

A modification which involves a change in storm water management control methods or techniques, or which involves the relocation or redesign of control measures, or which is necessary because soil or other conditions are not as stated on the approved plan, shall require the submission of a revised plan by the developer in accordance with the plan requirements as set forth in Article III of this Ordinance.

Section 610.10 Floodplains

A.                 Floodplain areas shall be established and preserved as provided by the Township Zoning Ordinance.

B.                 Whenever a floodplain is located within or along a lot, the plan shall include the following:

1.                  The boundary of the floodplain and the elevation or locational dimensions from the centerline of the watercourse;

2.                  A plan note that the floodplain shall be kept free of structures, fill and other encroachments; and, \

3.                  A plan note that floor elevations for all structures adjacent to the floodplain shall be two (2) foot above the one hundred (100) year flood elevation.