[Ord. 1402-12, 11/13/2012]
1. 
For all regulated activities, unless preparation of an SWM site plan is specifically exempted in § 17-302:
A. 
Preparation and implementation of an approved SWM site plan is required.
B. 
No regulated activities shall commence until the Borough issues written approval of an SWM site plan which demonstrates compliance with the requirements of this chapter.
2. 
All SWM site plans for regulated activities shall include such measures as necessary to:
A. 
Protect health, safety, and property.
B. 
Meet the water quality goals of this chapter, as set forth in § 17-103 hereof, by including measures that:
(1) 
Minimize disturbance to floodplains, wetlands, wooded areas, and existing vegetation.
(2) 
Maintain or extend riparian buffers.
(3) 
Avoid erosive flow conditions in natural flow pathways.
(4) 
Minimize thermal impacts to waters of the commonwealth.
(5) 
Disconnect impervious surfaces by directing runoff to pervious areas.
(6) 
Minimize soil disturbance and compaction.
C. 
Incorporate the techniques for low-impact development practices described in the Pennsylvania Stormwater best management practices Manual (BMP Manual).
3. 
Stormwater flows onto adjacent property shall not be created, increased, decreased, relocated, or otherwise altered without the written notification and written permission of the adjacent property owner(s) by the developer. Copies of all such notifications, permissions, licenses or easements shall be included in the SWM site plan submission.
4. 
For all regulated activities where erosion and sediment control is required in accordance with Title 25 of the Pennsylvania Code and the Clean Streams Law, the SWM site plan shall include the required erosion and sedimentation control measures. Necessary E&S BMPs shall be designed in accordance with the Erosion and Sediment Pollution Control Program Manual (E&S Manual), No. 363-2134-008 (March 2012), as amended and updated. Approval of the SWM site plan by the Borough shall be conditioned on the applicant obtaining erosion and sedimentation control approval from the appropriate agency(ies), when applicable.
5. 
For all regulated activities where NPDES permitting is required in accordance with the Clean Water Act (33 U.S.C. § 1251 et seq. [1972], as amended), the SWM site plan shall include the information required in the applicant's NPDES permit application. Approval of the SWM site plan by the Borough shall be conditioned on the applicant obtaining NPDES permit approval from the appropriate agency(ies), when applicable.
6. 
For all regulated activities, implementation of the volume controls in § 17-303 and the peak rate controls of § 17-304 is required unless exempt pursuant to § 17-302 hereof.
7. 
Special Management Areas. SWM site plans involving regulated activities within special management areas shall be prepared in a manner consistent with the guidance provided in Chapter 7 of the BMP Manual. The SWM site plan submission shall include design details for stormwater BMPs within said special management area.
8. 
An SWM site plan may propose that stormwater related to the proposed regulated activities be accommodated by existing stormwater management facilities on adjoining or nearby properties, provided that the SWM site plan documents the following:
A. 
The use of the stormwater BMPs located on said adjoining or nearby property is approved in writing by the owner of the property.
B. 
The stormwater BMPs located on said adjoining or nearby property are designed in a manner that can accommodate the stormwater management needs of the regulated activity in a manner consistent with all requirements of this chapter. The SWM site plan shall include all documentation necessary for the Borough to confirm such compliance.
9. 
SWM site plans, once approved by the Borough, shall remain on site throughout the duration of the regulated activity and be available for review as may be necessary by representatives of the Borough.
10. 
The design of all stormwater BMPs over karst geology shall include an evaluation of measures necessary to minimize adverse effects, including hydrogeologic studies if required by the Borough.
11. 
The Borough may, after consultation with and approval by DEP, approve measures for meeting the state water quality requirements other than those in this chapter, provided that they meet the minimum requirements of, and do not conflict with, state law, including, but not limited to, the Clean Streams Law. The Borough shall maintain a record of consultations with DEP pursuant to this provision. Notwithstanding the foregoing, the Borough is not required to consult DEP for a waiver of the requirements set forth in §§ 17-306, 17-307, 17-308 and 17-309 herein.
12. 
All natural streams, channels, swales, drainage systems and/or areas of surface water concentration shall be maintained in their existing condition unless an alteration is approved by the Borough. All encroachment activities shall comply with the requirements of 25 Pa. Code Chapter 105 (Water Obstructions and Encroachments),[1] of the rules and regulations promulgated by DEP. Any approvals or permits issued do not relieve compliance as referenced in § 17-108, Compatibility With Other Requirements.
[1]
Editor's Note: See now 25 Pa. Code Chapter 105, Dam Safety and Water Management.
13. 
The technical standards provided within this chapter are considered the baseline for design and layout of an SWM plan. Use of other alternative and innovate designs for controlling stormwater runoff may be permitted when approved by the Borough Engineer.
14. 
All existing stormwater management facilities and agreements shall continue to be maintained with the intended functionality as designed and approved.
15. 
All work shall be in accordance with the Borough's Construction and Material Specifications as approved and adopted from time to time by the Borough Council.
[Ord. 1402-12, 11/13/2012]
1. 
A property owner or developer of any regulated activity that meets the following exemption criteria may be, upon approval by the Gettysburg Borough Stormwater Authority, exempt from certain stormwater management requirements of this chapter. However, the property owner or developer shall be subject to all other requirements of this chapter other than related requirements for which an exemption or exemptions have been authorized. The criteria for exemption in this section apply to the total development proposed, including instances in which the development is proposed to take place in phases. The date of enactment of this chapter shall be the starting point from which future development and the respective exemption criteria shall be cumulatively considered and regulated.
[Amended by Ord. No. 1470-20, 5/11/2020]
A. 
Regulated activities that involve less than 800 square feet of impervious surface, where the total cumulative impervious surface added since the adoption date of this chapter is less than 800 square feet, may be exempted from portions of Article III, including volume control (§ 17-303) and peak rate control (§ 17-304) and may be exempted from all of Parts 4 and 5 of this chapter and the SWM site plan preparation and submission requirements of this chapter. The applicant shall complete requirements as defined by the Simplified Approach (see Appendix D, which is attached hereto and made a part of this chapter).
B. 
Regulated activities that involve more than 800 square feet up to 5,000 square feet of impervious surface, where the total cumulative impervious surface added since the adoption date of this chapter is less than 5,000 square feet, may be exempted from the peak rate control as set forth in § 17-304 of this chapter.
C. 
Agricultural activities shall be exempt from the rate control, volume control and SWM site plan preparation and submission requirements of this chapter, provided that the agricultural activities are performed in accordance with the requirements of 25 Pa. Code Chapter 102. Further, such activities shall not be subject to the exemption approval process of § 17-302, Subsection 2, of this chapter.
D. 
Forest management and timber operations shall be exempted from the rate control, volume control and SWM site plan preparation and submission requirements of this chapter, provided that the forest management and timber operations are performed in accordance with the requirements of 25 Pa. Code Chapter 102. Further, such activities shall not be subject to the exemption approval process of § 17-302, Subsection 2, of this chapter.
E. 
Regulated activities involving domestic gardening for single-family consumption shall be exempted from volume control, rate control, and SWM site plan preparation and submission requirements of this chapter. Further, such activities shall not be subject to the exemption approval process of § 17-302, Subsection 2, of this chapter.
F. 
In-kind repair, in-kind replacement, and maintenance of existing surfaces and structures shall be exempted from volume control, rate control, and SWM site plan preparation and submission requirements of this chapter. Further, such activities shall not be subject to the exemption approval process of § 17-302, Subsection 2, of this chapter.
G. 
An area of up to 800 square feet of permeable pavers, permeable pavement, and/or green roofs may be considered as pervious area and may be accounted for, as such, when considering exemptions provided in § 17-302, Subsection 1A and B of this chapter. At a minimum, the submittal of a minor stormwater management plan in accordance with Appendix D, which is attached hereto and made a part of this chapter, will be required for any such projects.
2. 
Authorization of Exemptions. The Borough shall determine, in accordance with the following requirements and process, whether the proposed regulated activity may be exempted from the requirements of this chapter.
A. 
The property owner or developer proposing the regulated activity shall submit, in writing on a form supplied by the Borough, a request for said proposed regulated activity to be exempted from allowable requirements of this chapter pursuant to § 17-302, Subsection 1. The written request shall identify the project and shall indicate the specific exemption criteria, as listed in § 17-302, Subsection 1, that apply to the project.
B. 
Upon receipt of the plans and documents required, the Gettysburg Borough Stormwater Authority or its designee shall either approve or deny the exemption request. If the exemption request is denied, the Gettysburg Borough Stormwater Authority or its designee shall direct the property owner or developer to submit the information required to demonstrate that the proposed regulated activity complies with the requirements of this chapter or meets the exemption criteria.
[Amended by Ord. No. 1470-20, 5/11/2020]
C. 
Exemption request approval shall be at the discretion of the Gettysburg Borough Stormwater Authority or its designee and shall be subject to the following:
[Amended by Ord. No. 1470-20, 5/11/2020]
(1) 
The Gettysburg Borough Stormwater Authority may deny any exemption request or suspend or revoke any approved exemption request at any time for any project where Borough believes that the proposed regulated activity poses a threat to public health, safety, property, or the environment.
(2) 
Approval of an exemption request does not relieve the property owner or developer from other applicable requirements of this chapter or of other Borough ordinances or regulations.
(3) 
The Borough reserves the right to deny an exemption request if a drainage problem is known or identified by the Borough to exist or is expected to exist downstream from the proposed regulated activity.
[Ord. 1402-12, 11/13/2012]
The low-impact development practices provided in the BMP Manual shall be utilized for all regulated activities. Water volume controls shall be implemented using the Design Storm Method in § 17-303, Subsection A.
A. 
The Design Storm Method (CG-1 in the BMP Manual) may be used for any size of regulated activity. This method requires detailed modeling to achieve the following standards:
(1) 
The post-development total runoff volume shall not increase for all storms equal to or less than the two-year, twenty-four-hour-duration precipitation.
(2) 
For modeling purposes:
(a) 
Existing (pre-development), nonforested pervious areas must be considered meadow within the regulated activity area unless the existing land use dictates a lower runoff condition.
(b) 
Twenty percent of existing impervious area within the regulated activity area, when present, shall be considered meadow in the model for existing conditions.
(3) 
Infiltration BMPs shall be designed pursuant to § 17-306, Subsections S and T.
B. 
Infiltration Alternative. Where infiltration is not possible due to soil characteristics or is not desirable given other characteristics, water quality control may be proposed as an alternative to strict adherence to the volume control standards of § 17-303 of this chapter. Where water quality control is proposed, the following standards shall be achieved:
(1) 
At a minimum, the following documentation shall be provided to justify the proposal to reduce the infiltration requirements:
(a) 
Description of and justification for field infiltration and permeability testing with respect to the type of test and test locations.
(b) 
An interpretive narrative describing existing soils of the site and their structure as these relate to the interaction between soils and water characteristics of the site. In addition to providing soil and soil profile descriptions, this narrative shall identify depth to seasonal water tables and depth to bedrock and provide a description of all subsurface elements (restrictive layers, geology, etc.) that influence the direction and rate of subsurface water movement.
(c) 
A qualitative assessment of the site's contribution to annual aquifer recharge shall be made, along with the identification of any restrictions or limitations associated with the use of designed infiltration facilities.
(d) 
The provided documentation must be signed and sealed by a qualified professional.
(2) 
Water quality BMPs shall be implemented on all permanent stormwater discharges from the proposed project site to achieve pollutant removal efficiencies in accordance with the following table. (Efficiency removal rating shall be based on a testing specification for particle size distribution as required per TARP Tier 1 and 2 protocol testing. The minimum design flow shall be based on the peak flow produced from one inch of rain as calculated.)
Required Pollutant Removal Efficiencies for Infiltration Alternatives
Pollutant Load
Units
Required Removal Efficiency
(%)
Total suspended solids (TSS)
Pounds
85%
Total phosphorus (TP)
Pounds
85%
Total nitrate (NO3)
Pounds
50%
(3) 
Design guidance from the most current version of the BMP Manual, or equivalent resource as pre-coordinated with the Borough, shall be consulted when choosing design criteria for water quality BMPs.
[Ord. 1402-12, 11/13/2012]
1. 
Post-development discharge rates shall not exceed the pre-development discharge rates for the one-, two-, five-, ten-, twenty-five-, fifty-, and one-hundred-year twenty-four-hour storms. If it is shown that the peak rates of discharge indicated by the post-development analysis are less than or equal to the peak rates of discharge indicated by the pre-development analysis for one-, two-, five-, ten-, twenty-five-, fifty-, and one-hundred-year, twenty-four-hour storms, then the requirements of this section have been met. Otherwise, the applicant shall provide additional controls as necessary to satisfy the peak rate of discharge requirement.
2. 
For computation of pre-development peak discharge rates:
A. 
Existing (pre-development) pervious areas must be considered meadow within the regulated area, unless the existing land use dictates a lower runoff condition.
B. 
Twenty percent of existing impervious area within the regulated activity area, when present, shall be considered meadow in the model for existing conditions.
C. 
The developer shall demonstrate that the flows for the one-, two-, five-, and ten-year-frequency storms peak rates are less than or equal to pre-development rates during the construction phase.
[Ord. 1402-12, 11/13/2012]
1. 
For the purposes of the Act 167 Storm Water Management (plan) elements and this chapter, design policy pertaining to stormwater management facilities for Pennsylvania Department of Transportation (PennDOT) roadways and associated facilities is provided in Section 13.7 (Antidegradation and Post Construction Stormwater Management Policy) of PennDOT Publication No. 13M, Design Manual Part 2 (August 2009), as developed, updated, and amended in consultation with the PDEP. As stated in DM-2.13.7.D (Act 167 and Municipal Ordinances), PennDOT roadways and associated facilities shall be consistent with Act 167 plans. DM-2.13.7.B (Policy on Antidegradation and Post-Construction Stormwater Management) was developed as a cooperative effort between PennDOT and DEP. DM-2.13.7.C (Project Categories) discusses the anticipated impact on the quality, volume, and rate of stormwater runoff.
2. 
Where standards in the Act 167 ordinance are impractical, PennDOT may request assistance from DEP, in consultation with the Borough and County, to develop an alternative strategy for meeting State water quality requirements and the goals and objectives of the Act 167 plan elements.
3. 
For the purposes of the Act 167 ordinance, road maintenance activities are regulated under 25 Pa. Code Chapter 102.
[Ord. 1402-12, 11/13/2012]
1. 
Off-Site Areas. Off-site areas proposed to drain through a proposed development site are not subject to release rate criteria when determining allowable peak runoff rates; however, on-site drainage facilities shall be designed to safely convey off-site flows through the development site. When conditions as described above are encountered, separate analysis for developed and off-site areas shall be made for comparison purposes.
2. 
On-Site Areas. On-site areas proposed to remain outside a regulated activity area shall be considered as existing conditions, without considering any reductions in cover type. When conditions as described above are encountered, separate analysis for these areas shall be made for comparison purposes.
3. 
Downstream Hydraulic Capacity Analysis. Any existing downstream hydraulic capacity analysis shall be conducted in accordance with this chapter.
A. 
All downstream facilities impacted by the total site area of the regulated activity shall be studied to determine if the facility has adequate capacity to handle existing and proposed flows. An impacted downstream facility is one to which the runoff from the total site area of the regulated activity comprises more than 50% of the total flow to such a facility. The study shall end at a perennial stream. Downstream facilities include, but are not limited to, man-made or natural swales and open channels, pipes, inlets, culverts, bridges and roadways.
B. 
If any private facility is found to be undersized, the applicant shall be responsible for updating the facility in coordination with the regulated activity and appropriate municipal representation.
4. 
Regional Detention Alternatives. For certain areas within the study area, it may be more cost effective to provide one control facility for more than one development site than to provide an individual control facility for each development site. The initiative and funding for any regional runoff control alternatives are the responsibility of prospective developers. The design of any regional control basins must incorporate reasonable development of the entire upstream watershed. The peak outflow of a regional basin would be determined on a case-by-case basis using the hydrologic model of the watershed consistent with protection of the downstream watershed areas.
5. 
Capacity Improvements of Local Drainage Networks. In certain instances, local drainage conditions may dictate more stringent levels of runoff control than those based upon protection of the entire watershed. In these instances, if the developer can prove that it would be feasible to provide capacity improvements to relieve the capacity deficiency in the local drainage network, then the capacity improvements could be provided by the developer in lieu of runoff controls on the development site. Any capacity improvements would be designed based upon development of all areas tributary to the proposed improvement and the capacity criteria specified in this chapter. In addition, all new development upstream of a proposed capacity improvement shall be assumed to implement the applicable runoff controls consistent with this chapter, except that all new development within the entire subarea(s) within which the proposed development site is located shall be assumed to implement the developer's proposed discharge control, if any.
6. 
Capacity improvements may be provided as necessary to implement any regional or subregional detention alternatives.
7. 
Where the potential for groundwater and/or surface water contamination exists, based on the proposed use of the regulated activity, safeguards shall be incorporated into the site.
A. 
For industrial or commercial sites where it is possible that toxic or hazardous substances may come into contact with stormwater runoff, pretreatment of the first-flush (first 1/2 inch) runoff over areas where industrial and commercial operations take place shall be provided. Pretreatment shall include means for separating light and heavy toxic and hazardous substances from the stormwater before the stormwater is conveyed to the general stormwater management facilities.
B. 
Infiltration systems may be used to handle runoff from commercial or industrial working or parking areas only after the first-flush stormwater from these areas has been pretreated for removal of toxic and hazardous substances.
8. 
Roof drains and sump pumps shall discharge to lawns, infiltration or vegetative BMPs, or pervious areas wherever/whenever possible. If the above discharge criteria cannot be met or when it is more advantageous to connect directly to streets, storm sewers or other stabilized conveyance designations, then the discharge will be permitted on a case-by-case basis by the Borough. All discharges shall be conveyed in a manner as to not cause water problems on adjoining property owners.
9. 
Subsurface detention facilities shall provide adequately designed pretreatment for removal of pollutants, oil, trash and debris. Appropriate supporting information shall be provided for all proposed devices. All subsurface facilities shall be designed such that access for inspection and cleaning of the facility can occur.
10. 
Inlets shall be placed on both sides of the street at low spots and at the upper side of street intersections to prevent stormwater from crossing an intersection. Other devices such as high-efficiency grates or perforated pipe may be required if conditions warrant. All inlets at low points along the roadway shall have a ten-inch curb reveal and shall be equipped with pavement base drain extending 50 feet in either direction, parallel to the center line of the roadway.
11. 
Manholes, inlets, headwalls, and endwalls shall conform to the requirements of PennDOT Publication 408, as modified by the adopted Borough standards.
12. 
Design Standards. Permanent detention and retention facilities shall be designed to meet the following standards:
A. 
The maximum permitted depth for dry detention or retention basins shall be six feet, measured from the bottom of the emergency spillway to the lowest point in the basin.
B. 
The minimum top width of all basin embankments shall be eight feet.
C. 
The maximum permitted side slopes for detention or retention basins shall be four horizontal to one vertical. In order to obtain a waiver for slopes steeper than 4:1, the plan must include a planting schedule to stabilize the embankments. The proposed vegetation shall be low-maintenance varieties.
D. 
Minimum Bottom Slope. All detention basins shall have a minimum bottom slope of 2% unless infiltration facilities are provided.
E. 
Any stormwater management facility (i.e., detention basin) designed to store runoff and requiring a berm or earthen embankment required or regulated by this chapter shall be designed to provide an emergency spillway to handle flow up to and including the one-hundred-year, twenty-four-hour design storm at post-development conditions, assuming the principal outlet structure to be clogged. The height of embankment must be set as to provide a minimum one foot of freeboard above the maximum elevation computed for the clogged orifice condition. Should any stormwater management facility require a dam safety permit under 25 Pa. Code Chapter 105, the facility shall be designed in accordance with 25 Pa. Code Chapter 105 and meet the regulations of 25 Pa. Code Chapter 105 concerning dam safety which may be required to pass storms larger than the one-hundred-year event.
F. 
A cutoff trench of impervious material shall be provided within all basin embankments.
G. 
Where a basin embankment is constructed using fill on an existing fifteen-percent or greater slope, the basin must be keyed into the existing grade.
H. 
Fencing. Any aboveground stormwater management detention/retention facility that is designed to store at least a two-foot depth of runoff shall be subject to the following fencing requirements:
(1) 
A stormwater facility must be completely surrounded by a chain-link fence of not less than four feet in height. Alternative fences and barriers may be permitted upon request to and approval by the Borough.
(2) 
All gates or doors opening through such enclosure shall be equipped with a self-closing and self-latching device for keeping the gate or door securely closed at all times, when not in actual use.
I. 
All outlet structures and emergency spillways shall include a satisfactory means of energy dissipation at its outlet to assure conveyance and flow without endangering the safety and integrity of the basin and the downstream drainage area.
J. 
A concentrated discharge of stormwater to an adjacent property shall be within a natural drainageway or watercourse, or an easement shall be required.
K. 
All facilities shall be provided with an access slope at no more than 5:1 along with an access easement.
L. 
Plans for infiltration must show the locations of existing and proposed septic tank infiltration areas and wells. A minimum of 10 feet separation from on-lot disposal systems (OLDS) infiltration areas, including replacement areas, is required; however, 25 feet is desirable. Infiltration rates shall be based upon perc and probe tests conducted at the site of the proposed facility.
M. 
Guards shall be provided on all intake and outfall structures as well as outlet structures. The guard bars shall be one-half-inch-diameter galvanized bars on six-inch centers attached to the structure with three-eights-inch-diameter stainless steel anchors.
N. 
All facilities shall specify a maintenance requirement that controls the growth of noxious and invasive plants as specified in Appendix B, which is attached hereto and made a part of this chapter.
13. 
All storage facilities shall completely drain both the volume control and rate control capacities over a period of time not less than 24 hours and not more than 72 hours from the end of the design storm. However, any designed infiltration at such facilities is exempt from the minimum twenty-four-hour standard, i.e., may infiltrate in a shorter period of time, so long as none of the stormwater flowing into the infiltration facility is discharged directly into the surface waters of the commonwealth. (Inordinately rapid infiltration rates may indicate the presence of large fractures or other conditions for which an additional soil buffer may be required.) Where extended detention facilities are utilized to mitigate increased volume, the increased volume is required to be detained not less than 24 hours from the end of the twenty-four-hour design storm (assuming the peak rate occurs at approximately the twelve-hour time period in the storm).
14. 
For all regulated activities, SWM BMPs shall be designed, implemented, operated, and maintained to meet the purposes and requirements of this chapter and to meet all requirements under Title 25 of the Pennsylvania Code, the Clean Streams Law, and the Storm Water Management Act.
15. 
Design for BMPs shall be in accordance with design standards as listed in the BMP Manual or other legitimate source.
16. 
Existing (pre-development) pervious areas must be considered meadow within the regulated area, unless the existing land use dictates a lower runoff condition.
17. 
Infiltration BMPs shall be spread out such that impervious to BMP loading ratios are less than or equal to 5:1, made as shallow as practicable, and located to maximize use of natural on-site infiltration features while still meeting the other requirements of this chapter.
18. 
Impervious Area.
A. 
The measurement of impervious areas shall include all of the impervious areas in the total proposed development, even if development is to take place in phases.
B. 
For development taking place in phases, the total proposed impervious for all phases must be used in determining conformance with this chapter.
C. 
For projects that add impervious area to a parcel, the total impervious area on the parcel is subject to the requirements of this chapter, except that the volume controls in § 17-303 and the peak rate controls of § 17-304 do not need to be considered for existing impervious areas that are not being altered by the proposed regulated activity.
D. 
Twenty percent of existing impervious area within the regulated area, when present, shall be considered meadow in the model for existing conditions.
19. 
Infiltration BMPs shall be designed in the following manner: A detailed soils evaluation of the project site shall be performed to determine the suitability of recharge facilities. The evaluation shall be performed by a qualified professional and, at a minimum, address soil permeability, depth to bedrock, susceptibility to sinkhole formation, and subgrade stability, seasonally high groundwater table, suitability of stormwater management facilities and maximum infiltration capacity in depth of water per unit area. The general process for designing the infiltration BMP shall be:
A. 
Site evaluation to determine general areas of suitability for infiltration practices.
B. 
Provide field tests throughout the area proposed for development to determine appropriate percolation rate and/or hydraulic conductivity. At least one infiltration test must be included in each soil group, and at least one infiltration test must be conducted for each five lots proposed for development. Infiltration tests must be taken at the location and depth of all proposed infiltration structures.
C. 
Design infiltration facility for required storm volume based on all available data.
D. 
The infiltration requirement in the high-quality/exceptional waters shall be subject to Title 25, Chapter 93, of the Pennsylvania Code of Regulations and the antidegradation regulations promulgated by DEP thereunder.
E. 
A double-ring infiltrometer test shall be used for all infiltration tests in accordance with the current edition of the BMP Manual.
20. 
Plans for infiltration must show the locations of existing and proposed septic tank infiltration areas and wells. A minimum twenty-five-foot separation from on-lot disposal systems (OLDS) infiltration areas, including replacement areas, is desired and will be evaluated by the municipality on a case-by-case basis. However, the separation shall not be less than DEP-required 10 feet.
[Ord. 1402-12, 11/13/2012]
1. 
Any stormwater facility located on State highway rights-of-way shall be subject to approval by the Pennsylvania Department of Transportation (PennDOT).
2. 
Any stormwater management facilities regulated by this chapter that would be located in or adjacent to waters of the commonwealth or wetlands shall be subject to approval by DEP through the joint permit application process or, where deemed appropriate by DEP, the general permit process. When there is a question 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 from DEP.
3. 
Any stormwater management facility located within the vicinity of a floodplain shall be subject to approval in accordance with 25 Pa. Code Chapter 106 (Floodplain Management) of the rules and regulations promulgated by DEP.
4. 
All earthmoving activities must be reviewed and approved by the Adams County Conservation District prior to commencing work.
5. 
The design of all stormwater management facilities shall incorporate good engineering principles and practices. The Borough shall reserve the right to disapprove any design that would result in the occupancy or continuation of adverse hydrologic or hydraulic conditions within the watershed.
6. 
The existing points of concentrated drainage that discharge onto adjacent property shall not be altered without written permission of the adjacent property owner(s) and shall be subject to any applicable discharge criteria specified in this chapter.
7. 
Areas of existing diffused drainage discharge shall be subject to any applicable discharge criteria in the general direction of existing discharge, whether proposed to be concentrated or maintained as diffused drainage areas, except as otherwise provided by this chapter. If diffused flow is proposed to be concentrated and discharged onto adjacent property, the developer shall 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.
8. 
Where a development site is traversed by watercourses, drainage easements shall be provided conforming to the line of such watercourses. 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, the maintaining of vegetation in a natural state within the easement shall be required, except as approved by the appropriate governing authority.
9. 
When it can be shown that, due to topographic conditions, natural conveyance facilities on the site cannot adequately provide for drainage, open channels may be constructed conforming substantially to the line and grade of such natural drainageways. Work within natural conveyance facilities shall be subject to approval by DEP through the joint permit application process or, where deemed appropriate by DEP, through the general permit process.
10. 
Special Requirements for Areas Falling Within Defined Exceptional Value and High-Quality Subwatersheds: The temperature and quality of water and streams that have been declared as exceptional value and high quality are to be maintained as defined in Chapter 93, Water Quality Standards, Title 25 of the Pennsylvania Code of Regulations. Temperature-sensitive BMPs and stormwater conveyance systems are to be used and designed with storage pool areas and supply outflow channels and should be shaded with trees. This will require modification of berms for permanent ponds and the relaxation of restrictions on planting vegetation within the facilities, provided that capacity for volumes and rate control is maintained. At a minimum, the southern half on pond shorelines shall be planted with shade or canopy trees within 10 feet of the pond shoreline. In conjunction with this requirement, the maximum slope allowed on the berm area to be planted is 10 to 1. This will lessen the destabilization of berm soils due to root growth. A long-term maintenance schedule and management plan for the thermal control BMPs is to be established and recorded for all development sites within defined exceptional value and/or high-quality subwatersheds.
[Ord. 1402-12, 11/13/2012]
1. 
Stormwater runoff hydrographs/peak rates shall be calculated in the following manner:
A. 
For the purpose of considering peak flows with a fully developed runoff hydrograph, the Soil Cover Complex Method TR-20 or TR-55 and a twenty-four-hour rainfall event shall be used with the appropriate design rainfall depths. A dynamic or interconnected model is required for modeling of multiple drainage or subareas. The SCS Rainfall Type II curve or local precipitation frequency data shall be used for the rainfall distribution. The Borough may allow the use of other methodologies on a case-by-case basis as approved prior to design submittal.
B. 
Times of concentration shall be calculated using the methodology presented in Chapter 3 of Urban Hydrology for Small Watersheds, NRCS, TR-55 (as amended or replaced from time to time by NRCS).
C. 
The design storm volumes to be used in the analysis of peak rates of discharge shall be obtained from the Precipitation-Frequency Atlas of the United States, Atlas 14, Volume 2, Version 3.0, as amended and updated, U.S. Department of Commerce, National Oceanic and Atmospheric Administration (NOAA), National Weather Service, Hydrometeorological Design Studies Center, Silver Spring, Maryland. NOAA's Atlas 14 can be accessed at: http://hdsc.nws.noaa.gov/hdsc/pfds/.
D. 
Runoff curve numbers (CN) for both existing and proposed conditions to be used in the Soil Cover Complex method shall be obtained from Appendix C, Table 1, which is attached hereto and made a part of this chapter.
E. 
The design of any stormwater detention facilities intended to meet the performance standards of this chapter shall be verified by routing the design storm hydrograph through these facilities, using either manual methods or computerized routing. Routing shall be based upon the Modified Puls Method; other routing methodologies shall be subject to the approval of the Borough Engineer.
2. 
Conveyance facilities shall be designed in the following manner:
A. 
All storm drain systems, streets, and inlets (excluding detention and retention basin outfall structures) shall be designed for a ten-year storm event. Sole-access structures (culverts and bridges) shall be designed to convey the twenty-five-year flood without overtopping the roadway.
(1) 
When a pipe or culvert is intended to convey to or pass the discharge from a stormwater management facility, its required capacity shall be computed using the methodology considered for the stormwater management facility design as part of a dynamic model.
(2) 
Greater design frequencies may be justified on individual projects.
(3) 
A one-hundred-year storm frequency may be required for design of the stormwater collection system to insure that the resultant stormwater runoff from the post-development storm is directed into the management facility.
(4) 
If the Rational Method is used for calculating peak flows, conveyance facilities 30 inches in diameter or less shall use a time of concentration of five minutes for the contributing drainage area shall be considered for the design.
B. 
In general, inlets shall be spaced such that, based upon the Rational Method, time of concentration (tc) equals five-minute and ten-year rainfall intensity; the area contributing to the inlet shall not produce a peak runoff of greater than four cubic feet per second (cfs). Also, inlets shall be spaced so that their efficiency, based upon efficiency curves published by the Pennsylvania Department of Transportation (PennDOT), is not less than 65%.
C. 
The Rational Method may be used for stormwater collection and conveyance facilities, provided that the facilities are part of an integrated SWM facility requiring modeling using SCS modeling. Rainfall intensities shall be consistent with appropriate times of concentration and return periods.
D. 
Runoff coefficients (C) for use with the Rational Method shall be obtained from Appendix C, Table 2, which is attached hereto and made a part of this chapter.
E. 
Existing and proposed channels or swales must be able to convey the increased runoff associated with a proposed one-hundred-year return period event within their banks at velocities consistent with protection of the channels from erosion. Acceptable velocities shall be based upon criteria included in the DEP Erosion and Sediment Pollution Control Program Manual.
F. 
Existing natural or man-made channels or swales must be able to convey proposed one-hundred-year return period runoff without creating any hazard to persons or property.
G. 
Stormwater runoff on roadways (i.e., gutter spread, lane encroachment, etc.) shall be controlled in accordance with PennDOT Publications 13M, "Design Manual, Part 2," and 584, "Drainage Manual."
H. 
In all cases where drainage is picked up by means of a headwall, the pipe shall be designed as a culvert. Inlet and outlet conditions shall be analyzed. The minimum diameter of a culvert shall be 18 inches. The procedure contained in Hydraulic Engineer Circulars No. 5 and No. 13, as prepared by the U.S. Department of Transportation, Federal Highway Administration, Washington, D.C., shall be used for the design of culverts. All culverts shall include concrete headwalls and endwalls.
[Ord. 1402-12, 11/13/2012]
In areas of carbonate geology, a geologist shall certify to the following:
A. 
No stormwater management facility will be placed in, over, or immediately adjacent to the following features:
(1) 
Closer than 100 feet from sinkholes;
(2) 
Closer than 100 feet from closed depressions;
(3) 
Closer than 100 feet from caverns, intermittent lakes, or ephemeral streams;
(4) 
Closer than 50 feet from lineaments in carbonate areas;
(5) 
Closer than 50 feet from fracture traces; or
(6) 
Closer than 25 feet from bedrock pinnacles (surface or subsurface).
B. 
Stormwater resulting from regulated activities shall not be discharged into sinkholes.
C. 
If the developer can prove through analysis that the project site is an area underlain by carbonate geology, and such geologic conditions may result in sinkhole formations, then the project site is exempt from recharge requirements as described in § 17-303, Volume Controls. However, the project site shall still be required to meet all other standards found in this chapter.
D. 
It shall be the developer's responsibility to verify if the project site is underlain by carbonate geology. The following note shall be attached to all stormwater management plans and signed and sealed by the developer's geologist: "I, __________, certify that the proposed stormwater management facility (circle one) is/is not underlain by carbonate geology."
E. 
Whenever a stormwater management facility will be located in an area underlain by carbonate geology, a geological evaluation of the proposed location by a qualified licensed professional shall be conducted to determine susceptibility to sinkhole formation and the possibility of groundwater contamination from the facility.
[Ord. 1402-12, 11/13/2012]
Where an applicant proposes to utilize riparian buffers as the means to meet the requirements of this chapter, said riparian buffers shall be established and/or maintained in accordance with the BMP Manual or the publication Riparian Forest Buffer Guidance, published November 2010 by DEP, and as may be amended or updated.
[Ord. 1402-12, 11/13/2012]
1. 
Any drain or conveyance, whether on the surface or subsurface, that allows any nonstormwater discharge, including sewage, process wastewater, and wash water, to enter the waters of the commonwealth is prohibited.
2. 
No person shall allow, or cause to allow, discharges into surface waters of the commonwealth which are not composed entirely of stormwater, except 1) as provided in Subsection 17-311.3 below and 2) discharges allowed under a state or federal permit.
3. 
The following discharges are authorized unless they are determined to be significant contributors to pollution to the waters of the commonwealth:
Discharges from firefighting activities
Potable water sources, including water line flushing
Irrigation drainage
Air-conditioning condensate
Springs
Water from crawl space pumps
Pavement wash waters where spills or leaks of toxic or hazardous materials have not occurred (unless all spill material has been removed) and where detergents are not used
Diverted stream flows
Flows from riparian habitats and wetlands
Uncontaminated water from foundations or from footing drains
Lawn watering
Dechlorinated swimming pool discharges
Uncontaminated groundwater
Water from individual residential car washing
Routine external building wash-down (which does not use detergents or other compounds)
Water discharged in well testing for potable water supplies
4. 
In the event that the Borough or DEP determines that any of the discharges identified in Subsection 3 significantly contribute to pollution of the waters of the commonwealth, the Borough or DEP will notify the responsible person(s) to cease the discharge.
[Ord. 1402-12, 11/13/2012]
No person shall modify, remove, fill, landscape, or alter any stormwater BMPs, facilities, areas, or structures in a manner, without the written approval of the Borough, with the exception of necessary maintenance activities such as mowing.