(A)   General provisions.
      (1)   Stormwater runoff from any subdivision or land development (including during construction and earthmoving) shall not occur at a peak rate (measured in cubic feet per second) that is greater after development than occurred prior to development.
      (2)   Control of runoff from a site shall occur using appropriate means of detention of the water on the site and/or other approved types of stormwater management, within the requirements of this chapter.
      (3)   Runoff that is detained shall be held and released at a predetermined controlled rate by appropriately installed devices. The release shall be in the same manner as the natural or predevelopment means of discharge from a site (such as point discharge or sheet flow).
      (4)   Stormwater runoff shall not be increased or redirected in such a way that it results in hazards to persons or property or interferes with the normal movement of vehicles.
      (5)   All stormwater management methods are subject to approval by the Borough Engineer.
      (6)   Stormwater shall be directed away from buildings and on-lot septic systems.
      (7)   All stormwater management plans shall take into account and provide for existing flow from upstream areas within the entire watershed.
      (8)   The existing points of natural drainage discharge onto adjacent property shall not be altered nor shall the concentration of water runoff be increased because of development without the written approval of all affected landowners.
      (9)   No stormwater runoff or natural drainage water shall be so diverted as to overload existing drainage systems, or create flooding or the need for additional drainage structures on other private properties or public lands, without complete approval of provisions being made by the developer for properly handling such conditions, including water runoff impoundments, if necessary.
      (10)   All lots shall be laid out and graded to prevent cross lot drainage, to provide positive drainage away from proposed building locations and any primary or alternate septic system locations.
      (11)   An adequate storm sewer system consisting of inlets and other underground drainage structures with approved outlets shall be constructed where the runoff of stormwater and the prevention of erosion cannot be accomplished satisfactorily by surface drainage facilities, as determined by the Borough Council, based upon the recommendation of the Borough Engineer.
      (12)   Outlet locations shall be approved by the Borough Engineer.
      (13)   Sequence of construction: no substantial grading shall occur and no building permits shall be issued for any building unless any detention basin, siltation basin or improved major swale approved to handle the resulting runoff is in place. Any detention basin shall be seeded and stabilized and have an installed outlet structure prior to the construction of any streets or buildings within that drainage basin.
   (B)   Calculations of stormwater runoff.
      (1)   Stormwater calculations shall be submitted in a clear and legible manner for any lot or tract that would result in more than 5,000 square feet of total impervious cover.
      (2)   (a)   These calculations shall follow a method preapproved by and acceptable to the Borough Engineer.
         (b)   The following methods are recommended:
            1.   Rational Method; and
            2.   Soil cover complex method. See U.S. Soil Conservation Service Technical Release No. 55 Urban Hydrology for Small Watersheds.
      (3)   Rainfall data shall be from PennDOT, for the Lehigh Valley.
      (4)   The stormwater calculations shall include the following:
         (a)   Pre- and post-development drainage maps showing existing and proposed grades and including any off-site tributary area;
         (b)   Pre- and post-development runoff calculations;
         (c)   Detention basin design calculations (as applicable);
         (d)   Pipe and swale sizing calculations;
         (e)   All other information that is needed to construct proposed stormwater drainage facilities, including, but not limited to, slopes, proposed elevations, typical cross-sections and details;
         (f)   Such information as the Borough Engineer determines is needed to determine compliance with this chapter; and
         (g)   If the development occurs in phases, the entire system shall be shown.
      (5)   Where crop farming or disturbed earth exists on the site prior to development, meadow in good condition shall be used as the starting base for the calculation.
   (C)   Design storms. The following shall apply unless superceded by PennDOT or other stricter standards.
      (1)   At a minimum, the applicant shall prove to the satisfaction of the Borough Engineer that no increase in peak stormwater discharge will leave the tract during earthmoving, construction or after development than occurred prior to any of these activities, under the following conditions and storm frequencies (considered individually), unless any more restrictive requirements of an applicable official stormwater management plan adopted by DEP and the county pursuant to the Stormwater Management Act, 32 P.S. §§ 680.1 et seq., as amended:
         (a)   Two-year storm;
         (b)   Five-year storm;
         (c)   Ten-year storm;
         (d)   Twenty-five-year storm;
         (e)   Fifty-year storm;
         (f)   One hundred-year storm; and
         (g)   If using the SCS calculation method, a 24-hour Type II storm shall be used in the calculations required by this division (C)(1).
      (2)   Storm sewer piping, roadside swales and inlet systems shall be designed for a 25-year storm. A 24-hour Type II rainfall shall be used if using the soil complex method. The openings of culverts and under bridges shall be designed for a 50-year, 24-hour type II rainfall (except within the 100- year floodplain). Bridges shall be designed with one foot of freeboard.
      (3)   Within the 100-year floodplain, any stormwater management structures and systems shall be designed to handle a 100-year storm. A 24-hour Type II storm shall be used if using the soil complex method.
      (4)   The stormwater management plan shall show that a 100-year, 24-hour storm can be safely conveyed without jeopardizing any principal building on or adjacent to of the site.
   (D)   Design submission.
      (1)   All plans showing the proposed storm drainage construction must be accompanied by a complete design stamped and signed by a state registered engineer or registered landscape architect.
      (2)   When subdivisions or land developments are submitted to the borough for approval in sections, a complete general storm sewer design for the proposed subdivision or land development shall be submitted at the preliminary plan level. The proposed design must take into account the entire tract and the watershed.
      (3)   All stormwater controls shall be designed to function adequately after the completion of each phase of a development. This may require the use of temporary structures, which shall be shown on submitted plans.
      (4)   A development shall be required to include the construction of stormwater controls in areas of future phases of a development prior to construction of earlier phases if the Borough Engineer determines that that is necessary to make sure that the system will work after the completion of each phase. This shall, for example, include the extension of the main outfall line.
      (5)   A set of approved design plans shall be maintained on file at the site during construction.
      (6)   Drainage structures that are located on state highway rights-of-way shall be found to be acceptable to PennDOT, and PennDOT approval shall be a condition of any final approval of the borough.
      (7)   Submission requirements: the submission requirements for stormwater management plans for preliminary and final plans within §§ 154.075 through 154.078 and 154.090 through 154.093 shall apply to all required submissions under this section.
   (E)   County watershed plans. For areas of a development that are located within a watershed for which a stormwater management plan has been adopted by DEP and the county (pursuant to the State Stormwater Management Act), the county plan shall supercede any conflicting parts of this section. This specifically includes reconsideration of detention of stormwater where the county plan so recommends.
   (F)   Joint storm drainage facilities.
      (1)   Stormwater management facilities may be planned and constructed in coordination by two or more developments, provided that all other parts of this section are complied with and a process to ensure maintenance is established that is acceptable to the Borough Council.
      (2)   The borough may require a development to contribute its fair share of the costs of a comprehensive regional or subregional stormwater system in place of requiring an on-site detention basin.
   (G)   Methods of detention and flow delay.
      (1)   The following methods of detention or flow-delay devices may be found to be acceptable by the Borough Engineer:
         (a)   Wet or dry ponds and detention basins;
         (b)   Roof storage and increased roof roughness;
         (c)   Parking lot detention;
         (d)   Infiltration trenches;
         (e)   Porous pavements, grassed channels and vegetated strips;
         (f)   Cisterns, underground reservoirs or covered ponds;
         (g)   Increasing the roughness coefficients on the development’s surface area;
         (h)   Decrease percentage of impervious area;
         (i)   Groundwater recharge;
         (j)   Routing flow over lawns in swales within stormwater easements;
         (k)   Detention storage within the storm sewer; and
         (l)   Another method that may be approved by the Borough Engineer.
   (H)   Rooftop storage. If a roof is to be used for detention, a condition of such use shall be that the applicant submit appropriate calculations and a signed statement from a registered architect or registered engineer that the structure will be able to support the roof loadings. This statement shall be required prior to issuance of the building permit.
   (I)   Parking lot storage. A maximum of 30% of paved parking lot may be found acceptable as a stormwater detention but not retention facility. Ponding shall be arranged so that pedestrians may cross the parking lot relatively dryly. There shall be a maximum designed depth of six inches, and the pavement shall be designed to withstand the effects of ponded water. The area used for the storage shall be the least used portions of the parking.
   (J)   Groundwater recharge. In general, all runoff control measures shall be designed to encourage groundwater recharge, if suitable subsurface conditions are present. However, in any such recharge, proper precautions shall be taken to prevent pollution of the groundwater, prevent the formation of sinkholes and to promote safety.
   (K)   Detention basins standards.
      (1)   Generally. For the purpose of this section, a retention basin shall be required to meet the same standards as a detention basin.
      (2)   Emergency spillways. All detention basins shall be designed with an emergency spillway.
         (a)   These spillways at a minimum shall be able to handle a 100-year post-development peak discharge.
         (b)   Whenever possible, the emergency spillway for detention basins shall be constructed on undisturbed ground. If the emergency spillway cannot be constructed on undisturbed ground, it shall be constructed of suitable material adequately compacted in accordance with specifications preapproved by the Borough Engineer.
         (c)   Emergency spillways shall be constructed of reinforced concrete, vegetated earth or concrete rubble. All emergency spillways shall be constructed so that the detention basin berm is protected against erosion.
         (d)   The emergency spillway shall be a minimum of two feet below the adjacent berm elevation. The emergency spillway shall convey the 100-year storm at a maximum depth of one foot over spillway. The downstream slope of the spillway shall as a minimum extend to the toe of the berm embankment. The edge of the basin grading shall be within the subject property.
         (e)   All detention basin outflow structures shall be designed with trash racks over the outflows.
      (3)   Slope of detention basin embankment. The maximum inside slope of earthen detention basin embankments shall be four horizontal to one vertical. The maximum outside slope shall be three to one. The top or toe of any slope shall be located a minimum of five feet from any property line. Whenever possible the side slopes and basin shape shall be amenable to the natural topography. Straight side slopes are prohibited.
      (4)   Width of berm. The minimum top width of detention basin berms shall be ten feet, unless the Borough Engineer determines that a greater width is needed for maintenance and/or structural purposes.
      (5)   Slope of basin bottom. In order to ensure proper drainage of the detention basin, a minimum grade of 2% shall be maintained for all sheet flow. A minimum grade of 1% shall be maintained for all channel flow, provided that a synthetic low flow channel of suitable materials is provided.
      (6)   Antiseep collars. Antiseep collars shall be installed around the principal pipe barrel within the normal saturation zone of the detention basin berms. Antiseep collars shall not be required on basins designed to have a depth of water of less than three feet. The antiseep collars and their connections to the pipe barrel shall be watertight. The antiseep collars shall extend a minimum of two feet beyond the outside of the principal pipe barrel. The maximum spacing between collars shall be ten times the minimum projection of the collar measured perpendicular to the pipe.
      (7)   Fencing.
         (a)   A detention basin shall be required to be surrounded with galvanized vinyl clad chain link metal fencing or an alternative type of fence acceptable to the borough if any of the conditions are present:
            1.   The maximum depth of water in the basin after a ten- or 25-year storm is greater than 30 inches;
            2.   The basin is intended to hold water for periods of longer than three hours after the rainfall subsides; and
            3.   The basin is to be dedicated to the borough and the Borough Council request fencing.
         (b)   Fencing of a detention basin under division (K)(7)(a) above shall not be required if the nearest residential district, school, existing residence or recreation facility is at least 1,500 feet away in walking distance from the basin.
      (8)   Landscaped screening of detention basins.
         (a)   A detention basin shall be screened from view of existing residences, a residential zoning district or a public street, unless the basin would meet all of the following conditions:
            1.   It would have an average inside slope of less than four to one on the inside of the basin;
            2.   Either:
               a.   The inside and outside of the berm of the basin would be mowed grass or other attractive vegetative ground cover; or
               b.   The basin would be designed to closely resemble a natural pond.
            3.   It would not be surrounded by a primarily metal fence.
         (b)   Any required screening shall meet the “buffer yard” standards of the borough zoning ordinance (as adopted by reference in Chapter 155 of this code of ordinances). This landscaping is not required where natural vegetation. that will completely fulfill this purpose will be maintained.
      (9)   Multiple basins. The use of multiple detention basins should be investigated over the use of one larger storage facility.
      (10)   Outflow structures. All outflow structures from storage facilities shall be equipped with a regulatory device that will permit modification to regulate the amount of out-flow. Suitable anti-vortex and/or velocity retarders shall be used.
      (11)   Outflow control structure. An outflow control structure shall be provided at the outlet of all detention basins. This structure shall be constructed of metal or concrete and shall be designed so that the rate of outflow is controlled by the pipe barrel through the basin berm when the depth of water within the basin exceeds the height of the structure. A trash rack or similar device shall be provided to prevent debris from entering the outflow structure. The crest elevation shall be set at a minimum of 12 inches below the emergency spillway.
      (12)   Retention basins. Aeration devices may be required, dependent upon the quality of the influent and detention time.
      (13)   Recreation. When reasonable, efforts should be made to allow suitable recreational uses of portions of detention areas. This might include designing a detention basin so that only a portion would be wet after a minor storm, and the remainder would be well-drained during all except the most serious storms. These areas may be acceptable at the discretion of the borough as part of any recreation land that may be required under this chapter.
      (14)   Placement. Detention basins shall not be placed within:
         (a)   An existing sinkhole;
         (b)   A location likely to be highly vulnerable to sinkholes; or
         (c)   Distinct topographic depression within a carbonate geology area, without a suitable liner or other engineering measures acceptable to Borough Council, based upon advice of the Borough Engineer.
   (L)   Construction standards. Construction and materials of storm drainage and control facilities (including pipes) and erosion control facilities shall be in accordance with the approved plans and any accompanying specifications. The construction details and standards of the following publications, or their sucessor publications, in their most recent revision shall be used:
      (1)   County Erosion and Sedimentation Control Handbook;
      (2)   PennDOT, Form 408, Specifications;
      (3)   PennDOT, RC Series, Roadway Construction Standards; and
      (4)   In cases where the above documents and/or borough specifications conflict, the more restrictive shall apply, except in areas of PennDOT jurisdiction.
   (M)   Storm sewers.
      (1)   The construction of new storm sewers or the connection into acceptable existing storm sewers shall be required or allowed by the Borough Council if the Borough Council determines on the basis of the recommendation of the Borough Engineer that this is the most feasible and reasonable option.
      (2)   Any storm sewers shall be constructed to borough specifications and shall not interconnect with sanitary sewers.
   (N)   Drainage pipe, culvert and catch basin design.
      (1)   Minimum diameter. The minimum diameter of any cross drainage or culvert pipe shall be 15 inches.
      (2)   Open pipe ends. Open pipe ends shall be fitted with concrete end walls, prefabricated end sections, rip-rap and/or energy disappators, as deemed appropriate by the Borough Engineer.
      (3)   Drainage pipes. Drainage pipes shall have a minimum slope of 0.5% and drainage swales and gutters 2.0%. As a minimum, the tops of all pipes should be at the same elevation when changing pipe sizes.
      (4)   Manholes. Manholes or inlets shall be used at all changes in horizontal alignment, at changes of vertical grade and at all pipe intersections. No run of pipe shall exceed 400 feet in length, without appropriate measures to allow cleanout. Trash racks shall be placed on all stormwater entrance structures.
      (5)   Bridges and culverts. Bridges and culverts shall meet PennDOT construction standards. DEP shall be contacted to determine if a dams and waterways permit is required.
      (6)   Grating. Appropriate safety grates shall be attached to all catch basins, stormwater inlets, pipe openings and other stormwater receiving structures, as needed, to ensure that maximum openings do not exceed 25 square inches. Along streets and pedestrian areas, bicycle safe grates shall be used as needed.
      (7)   Storm sewer outfall. Storm sewer outfalls shall be designed, with respect to the elevation of the invert or other features, that when the receiving watercourse is within a 25-year storm, the storm sewer will continue to drain the area it is designed to serve.
      (8)   Parallel ditches, swales and inlet spacing.
         (a)   To minimize sheet flow of stormwater across lots located on the lower side of streets, and to divert flow away from building areas, the cross-section of the street as constructed shall provide for parallel ditches or swales or curbing on the lower side which shall discharge only at drainage easements.
         (b)   Inlet spacing shall be designed such that in a 25-year storm, one traffic lane of at least ten feet in width shall be free from stormwater.
   (O)   Stormwater easements. See also § 154.165.
      (1)   Where a subdivision or development is traversed by a watercourse, drainageway, channel or stream that the Borough Engineer determines is subject to significant stormwater flows, a drainage easement shall be provided along the following:
         (a)   The 100-year floodway where that is defined;
         (b)   Where a 100-year floodway is not defined, the 100-year floodplain; and
         (c)   Where the 100-year floodplain is not defined, a 20 feet width shall be used on either side of the center of the watercourse, unless the Borough Engineer requires or permits a differing width.
      (2)   The drainage easements required by this section are intended to preserve the unimpeded flow of natural drainage and to provide for future possible widening, deepening, relocating, improving or protecting of such drainage facilities. The Borough Engineer may require up to one-half-foot freeboard if deemed necessary along newly constructed watercourses.
      (3)   Structures and other obstructions to flow (except fences made of materials and placed so as to not obstruct flow) shall be prohibited within stormwater easements. Such easements shall grant the borough the right to enter the easement to accomplish maintenance work, although the borough assumes no responsibility for such work.
      (4)   It shall be the responsibility of the applicant to obtain all stormwater easements on, over or through other properties that are needed to carry out the proposed storm management plan.
      (5)   Areas where stormwater easements have or will be granted shall not be obstructed during or after construction.
   (P)   Surface waters.
      (1)   Generally. All natural streams, channels, swales, drainage systems and/or areas of concentration of surface water shall be maintained in their existing condition unless alteration is approved by the Borough Engineer. The applicant shall be responsible to obtain all necessary DEP permits (see 25 Pa. Code Chapter 105).
      (2)   Creek alignments. Any change to the alignment of a watercourse, or any blocking, impeding or redirecting of a watercourse shall only occur with written approval of DEP and the Borough Engineer.
   (Q)   Ownership and maintenance of stormwater facilities. A system for the ownership and maintenance responsibilities of all temporary and permanent stormwater facilities and erosion and sedimentation control facilities that is satisfactory to the Borough Council shall be established prior to final plan approval including:
      (1)   Description of temporary and permanent maintenance requirements;
      (2)   Identification of responsible individual, corporation, association or other entity for ownership and maintenance of both temporary and permanent stormwater management and erosion and sedimentation control facilities;
      (3)   Establishment of suitable easements for access to all facilities;
      (4)   Where the grading and storm drainage plan proposes borough ownership and/or maintenance, a description of the methods, procedures and the extent to which any facilities shall be turned over to the borough, including a written approval and agreement from the borough indicating acceptance of responsibilities as proposed, shall be incorporated as an integral part of the plan;
      (5)   (a)   The borough may, at the complete discretion of the Borough Council, accept or not accept an offer by the applicant for borough ownership of stormwater facilities; and
         (b)   If the borough accepts ownership and maintenance responsibilities for stormwater facilities, the applicant shall be required by the Borough Council to fund a dedicated account to fund the first 25 years of such maintenance. This funding shall be based upon a reasonable estimate by the borough staff or the Borough Engineer.
      (6)   Stormwater facilities shall be designed to require minimal maintenance and shall have suitable access for maintenance;
      (7)   All storm drainage facilities shall be properly maintained by the party designated as responsible on the final subdivision plan, unless the Borough Council agree to accept a change in the party responsible or the party owning the facility;
      (8)   Should a facility not be maintained in proper working order, the Borough Council, may after due notice to the responsible party, arrange for the needed maintenance to be accomplished with all such expenses charged to the responsible party. These expenses shall be collectible as municipal claims are now collected by law; and
      (9)   The Borough Engineer and Code Enforcement staff shall have the right to enter private property to inspect storm drainage facilities. Reasonable effort should be made to contact the property owner prior to any such inspection.
(Ord. passed 2-3-1992)