Township of Brecknock, PA Design Criteria for Stormwater Management Facilities

Editor's Note: This ordinance also provided for the redesignation of former Subsection F as Subsection H.

For all regulated activities, erosion and sediment control and stormwater management 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 and the Clean Streams Law. Various BMPs and their design standards are listed in the Erosion and Sediment Pollution Control Program Manual (E&S Manual), No. 363-2134-008 (March 2012), as amended and updated, and the BMP Manual.

[Added 4-8-2014 by Ord. No. 198-2014]

Carbonate geology. In areas of carbonate geology, a registered professional geologist shall certify the following:

No stormwater facilities shall be placed in, over or immediately adjacent to the following features:

Sinkholes.

Closed depressions.

Lineaments in carbonate areas.

Fracture traces.

Caverns.

Intermittent lakes.

Ephemeral streams.

Bedrock pinnacles (surface or subsurface).

Stormwater management basins shall not be located closer than 100 feet from the rim of sinkholes or closed depressions, nor within 100 feet from disappearing streams; nor shall these basins be located closer than 50 feet from lineaments or fracture traces; nor shall these basins be located closer than 25 feet from surface or identified subsurface pinnacles.

Stormwater resulting from regulated activities shall not be discharged into sinkholes.

If the developer can prove through analysis that the development site is in an area underlain by carbonate geology, and such geologic conditions may result in sinkhole formations, then the development site is exempt from recharge requirements as described in §§ 93-13D and G. However, the development site shall still be required to meet all other hydrologic and water quality management standards as found in this chapter.

It shall be the developer's responsibility to verify if the development site is underlain by carbonate geology. The following note shall be attached to all stormwater management site plans and signed and sealed by the developer's qualified professional: "I, ____________________, certify that the proposed detention basin (circle one) is/is not underlain by carbonate geology."

Whenever a stormwater facility will be located in an area underlain by carbonate geology, a geological evaluation of the proposed location by a registered professional geologist shall be conducted to determine susceptibility to sinkhole formation. The evaluation may include the use of impermeable liners to reduce or eliminate the separation distances listed in Subsections F(1) and F(2) above.

When there is a reasonable probability that a project will affect or be affected by carbonate geologic hazards, the Board of Supervisors shall require submission of a hydrogeologic report. In reaching a determination of whether a project will affect or be affected by carbonate geologic hazards, the Board of Supervisors shall consider the presence or absence of carbonate features in the vicinity of the project, the testimony of qualified expert witnesses, and such other reasonable information as may be available. When a hydrogeologic report is required, an aquifer test shall also be required. All hydrogeologic reports shall be prepared at the applicant’s expense by a licensed geologist qualified in such matters. Each hydrogeologic report shall meet the requirements specified in Chapter 110, Zoning, § 110-72, of the Brecknock Township Code.

[Added 4-9-2013 by Ord. No. 187-2013]

§ 93-13 Stormwater management performance standards.

[Amended 9-11-2007 by Ord. No. 165; 6-8-2010 by Ord. No. 172; 4-8-2014 by Ord. No. 198-2014]

General. The following general standards shall be applied to all development within Brecknock Township to promote flow attenuation, erosion and sediment control and flood control consistent with the Conestoga River Watershed Act 167 Plan and Lancaster County Act 167 Plan.

The developer of any development site in Brecknock Township that does not fall under the exemption criteria in § 93-19 and does not meet the definition of a small project shall submit a stormwater management site plan consistent with the Brecknock Township Stormwater Management Ordinance.

Preparation of a SWM site plan is required for all regulated activities, unless preparation and submission of the SWM site plan is specifically exempted or qualifies as a small project according to § 93-19. For activities requiring a SWM site plan, the following apply:

All SWM site plans shall be designed and certified by individuals registered in the Commonwealth of Pennsylvania and qualified to perform such duties based on education and training in hydrology and hydraulics.

No regulated activities shall commence until the Township issues unconditional written approval of a SWM site plan.

SWM site plans approved by the Township shall be on-site throughout the duration of the regulated activity.

Runoff from impervious areas shall be drained to previous areas of the development site.

Impervious areas.

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 stages or phases.

For development taking place in stages or phases, the entire development plan must be used in determining conformance with this chapter.

Any areas designed to initially be gravel or crushed stone shall be assumed to be impervious.

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 and peak rate controls of this chapter do not need to be retrofitted to existing impervious areas that are not being altered by the proposed regulated activity.

[Added 11-8-2022 by Ord. No. 231-2022]

Stormwater management facilities which involve a State Highway shall be subject to the approval of the PennDOT.

Stormwater management facilities located within or affecting the floodplain area or any watercourse shall also be subject to the requirements of the Township of Brecknock Zoning Ordinance, Chapter 110, Brecknock Township Floodplain Management Ordinance, Chapter 93, and any other applicable requirements of the Floodplain Management Act.

[Amended 3-8-2016 by Ord. No. 210-2016]

Stormwater runoff from a development site shall flow directly into a natural drainageway, watercourse, or into an existing storm sewer system, or onto adjacent properties in a manner similar to the runoff characteristics of the predevelopment flow. Maximum use shall be made of the existing on-site natural and man-made stormwater management facilities. Stormwater flows onto adjacent property shall not be created, increased, decreased, relocated, or otherwise altered without written notification of the adjacent property owner(s) by the developer. Such stormwater flows shall be subject to the requirements of this chapter, including the establishment of a drainage easement. Copies of all such notifications shall be included in SWM site plan submissions.

Stormwater runoff shall not be transferred from one watershed to another unless they are subwatersheds of a common watershed which join together within the perimeter of the development site, or the effect of the transfer does not alter the peak discharge (in conformance with the requirements of the Act 167 Plan) onto adjacent lands, or drainage easements from the affected landowners are provided.

(9)

All stormwater runoff flowing over the development site shall be considered in the design of the stormwater management facilities.

(10)

In accordance with Chapter 102, temporary facilities shall be included in the submitted plans for a phased section where the following conditions are met:

A regulated activity constitutes a subdivision or land development.

The final plan applications are submitted in sections.

Temporary facilities are required for construction of a section.

(11)

The Township may require additional stormwater control measures for stormwater discharges to special management areas including but not limited to:

Water bodies listed as "impaired" on Pennsylvania's Clean Water Act 303(d/305(b) Integrated List.

Any water body or watershed with an approved total maximum daily load (TMDL).

Critical areas with sensitive resources (e.g., state-designated special protection waters, cold water fisheries, carbonate or other groundwater recharge areas highly vulnerable to contamination, drainage areas to water supply reservoirs, source water protection zones, etc.)

(12)

All regulated activities, including those exempt from SWM site plan preparation, shall include such measures as necessary to:

Protect health, safety, and property;

Meet the water quality goals of this chapter by implementing measures to:

Protect and/or improve the function of floodplains, wetlands, and wooded areas.

Protect and/or improve native plant communities including those within the riparian corridor.

[3]

Protect and/or improve natural drainageways from erosion.

[4]

Minimize thermal impacts to waters of this commonwealth.

[5]

Disconnect impervious surfaces by directing runoff to pervious areas, wherever possible.

Incorporate methods described in the Pennsylvania Stormwater Best Management Practices Manual (BMP Manual).

[Added 11-8-2022 by Ord. No. 231-2022]

Applicants shall provide infiltration facilities or utilize other techniques which will allow the post-development one-hundred-year hydrograph to match the predevelopment one-hundred-year hydrograph, along all parts of the hydrograph, for the development site. To match the predevelopment hydrograph, the post-development peak rate must be less than or equal to the predevelopment peak rate, and the post-development runoff volume must be less than or equal to the predevelopment volume for the same storm event. A shift in hydrograph peak time of up to five minutes and a rate variation of up to 5% at a given time may be allowable to account for the timing affect of BMPs used to manage the peak rate and runoff volume. Volume control volumes as given in § 93-15F may be used as part of this option.

Detention/Infiltration standards (only if existing hydrograph can not be matched):

Postdevelopment rates of runoff from any regulated activity shall not exceed a given percentage of the peak rate of runoff prior to development for all design storms unless the preexisting hydrograph is not exceeded at all points in time. The percentage of the predevelopment peak rate which may be released is known as the release rate. The areas of the watershed for which a certain release rate applies can be found in Appendix E, Subwatershed Boundary Map.[1]

Editor's Note: Appendix E is included at the end of this chapter.

Any portion of the volume control storage that is designed according to the infiltration standards in § 93-15F and is available within 24 hours from the end of the design storm based on the stabilized infiltration rate and/or the evapotranspiration rate may be also utilized for rate control storage.

Peak rate control is not required for off-site runoff. Off-site runoff may be by-passed around the site provided all other discharge requirements are met. If offsite runoff is routed through rate control facilities, runoff coefficients for off-site discharges used to design those rate control facilities shall be based on actual land use assuming winter or poor land conditions.

Innovative methods for the control of stormwater runoff shall be explored. Various combinations of methods should be tailored to suit the particular requirements of the type of development and the topographic features of the development site. The following is a partial listing of detention and control methods which can be utilized in stormwater management systems where appropriate:

Detention basins.

Retention basins (subject to prior municipal approval).

Rooftop detention.

Parking lot storage.

Seepage pits, seepage trenches or other infiltration structures.

Concrete lattice block surfaces.

(g)

Grassed channels and vegetated strips.

(h)

Cisterns and underground reservoirs.

(i)

Routed flow over grass.

(j)

Decreased impervious surface coverage.

(k)

Bioretention areas.

The following principles shall be applied to the erosion and sediment pollution control plan and construction schedule to minimize soil erosion and sedimentation:

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

Whenever feasible, natural vegetation shall be retained and protected.

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

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

Drainage provisions shall accommodate the stormwater runoff both during and after construction.

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

Groundwater recharge.

Developed areas shall maintain groundwater recharge consistent with predevelopment conditions, dependent on hydrologic soil groups and impervious cover unless the developer can prove the inability of the development site to achieve recharge based on existing development site conditions. This volume of runoff is termed the "recharge volume" and is calculated in accordance with § 93-15F. Development sites where the postdeveloped impervious area is equal to or less than the predeveloped impervious area shall not be required to provide groundwater recharge volume.

Design of the stormwater management facilities shall provide for groundwater recharge to compensate for the reduction in the percolation that occurs when the ground surface runoff characteristics have been altered. A detailed geologic evaluation of the development site shall be performed to determine the suitability of recharge facilities. The evaluation shall be performed by a registered professional geologist, and shall, at a minimum, address soil permeability, depth to bedrock, susceptibility to sinkhole formation, and subgrade stability. Where pervious pavement is permitted for parking lots, recreational facilities, nondedicated streets, or other areas, pavement construction specifications shall be noted on the plan.

If the developer can prove through analysis that the development site is in an area underlain by carbonate geology, and such geologic conditions may result in sinkhole formations, then the development site is exempt from recharge requirements. However, the development site shall still be required to meet all other hydrologic and water quality management standards as found in this chapter.

The developer may use stormwater credits for Non-Structural BMPs in accordance with the BMP Manual. The allowable reduction will be determined by the Township.

Water quality. Developed areas will provide adequate storage and treatment facilities necessary to capture and treat a minimum of the runoff from the first 1.2 inches of rainfall. This volume of storage is the "water quality volume" and is calculated in accordance with § 93-15G. The recharge volume may be a component of the water quality volume. If the recharge volume is less than the water quality volume, the remaining water quality volume may be captured and treated by methods other than recharge/infiltration BMPs. The water quality volume must take a minimum of 24 hours to be discharged. Development sites where the postdeveloped impervious area is equal to or less than the predeveloped impervious area shall not be required to provide water quality volume unless required by NPDES Part II.

Riparian corridors.

In order to protect and improve water quality, a riparian corridor easement shall be created and recorded as part of any subdivision or land development that encompasses a riparian corridor.

Except as otherwise required by Chapter 102, the riparian corridor easement shall be measured to be the greater of the limit of the one-hundred-year floodplain or 35 feet from the top of streambank (on each side).

Minimum management requirements for riparian corridors.

Existing native vegetation shall be protected and maintained within the riparian corridor easement.

Whenever practicable, invasive vegetation shall be actively removed and the riparian corridor easement shall be planted with native trees, shrubs and other vegetation to create a diverse native plant community appropriate to the intended ecological context of the site.

The riparian corridor easement shall be enforceable by the Township and shall be recorded in the Lancaster County Recorder of Deeds Office, so that it shall run with the land and shall limit the use of the property located therein. The easement shall allow for the continued private ownership and shall count toward the minimum lot area as required by zoning, unless otherwise specified in the Brecknock Township Zoning Ordinance.[2]

Editor's Note: See Ch. 110, Zoning.

Any permitted use within the Riparian Corridor Easement shall be conducted in a manner that will maintain the extent of the existing one-hundred-year floodplain, improve or maintain the stream stability, and preserve and protect the ecological function of the floodplain.

The following conditions shall apply when public and/or private recreation trails are permitted within riparian corridors:

Trails shall be for nonimotorized use only.

Trails shall be designed to have the least impact on native plant species and other sensitive environmental features.

Septic drainfields and sewage disposal systems shall not be permitted within the riparian corridor easement and shall comply with setback requirements established under 25 Pa. Code Chapter 73.

Developers have the option to propose a regional stormwater management plan or participate in a regional stormwater management plan developed by others. A regional stormwater management plan may include offsite volume and rate control, as appropriate and supported by a detailed design approved by the Township in accordance with § 93-12F. A regional stormwater management plan must meet all of the volume and rate control standards required by this chapter for the area defined by the regional stormwater management plan, but not necessarily for each individual development site. Appropriate agreements must be established to ensure the requirements of this chapter and the requirements of the regional stormwater management plan are met.

Minimum floor elevations for all structures that would be affected by a basin, other temporary impoundments, or open conveyance systems where ponding may occur shall be two feet above the one-hundred-year water surface elevation. If basement or underground facilities are proposed, detailed calculations addressing the effects of stormwater ponding on the structure and water-proofing and/or flood-proofing design information shall be submitted for approval.

§ 93-14 Stormwater management facility and conveyance design standards.

[Amended 9-11-2007 by Ord. No. 165; 4-8-2014 by Ord. No. 198-2014]

Aboveground storage facilities. Aboveground storage facilities consist of all stormwater facilities which store, infiltrate/evaporate/transpire, clean or otherwise affect stormwater runoff and the top of which is exposed to the natural environment. Aboveground storage facilities are located above the finished ground elevation. Aboveground storage facilities do not include stormwater management facilities designed for conveyance or cisterns.

Basins shall be installed prior to any earthmoving or land disturbance that they will serve. The phasing of their construction shall be noted in the erosion and sedimentation control narrative and on the E&S Plan. Permanent vegetation shall be established prior to disturbance of any other land, unless the basin functions as an E&S device.

Design criteria. Aboveground storage facilities shall comply with the design criteria in the following table:

Aboveground storage facility design criteria
		Facility Depth
		Less than 2 feet	2 feet to 8 feet	Greater than 8 feet
(a)	Embankment Geometry
[1]	Top width (minimum)	5 feet	5 feet	8 feet
[2]	Interior side slope (maximum)	3:1	3:1	3:1
[3]	Exterior side slope (maximum)	3:1	3:1	3:1
(b)	Embankment construction
[1]	Key trench	Not required	Required	Required
[2]	Pipe collar	Not required	Required	Required
[3]	Compaction density	Not required	Required	Required
(c)	Internal Construction
[1]	Dewatering feature	Required	Required	Required
[2]	Pretreatment elements	Not required*	Required	Required
(d)	Outlet Structure
[1]	Pipe size (minimum)	6 inches	15 inches	18 inches
[2]	Pipe material	SLHDPE, PVC, RCP	SLHDPE, RCP	RCP
[3]	Pipe slope (minimum)	0.5%	1.0%	1.0%
[4]	Anticlogging devices	Required	Required	Required
[5]	Antivortex design	Not required	Required	Required
[6]	Watertight joints in piping?	No	Yes	Yes
(e)	Spillway Requirements
[1]	Spillway freeboard (minimum)	Not required	6 inches	6 inches
[2]	Width (minimum)	Not required	10 feet	20 feet
[3]	Width (maximum)	Not required	50 feet	50 feet
[4]	Spillway channel design	Not required	Required	Required
[5]	Routing of one-hundred-year storm	Permitted	Permitted	Permitted

*	Pretreatment required for infiltration BMPs unless shown to be unnecessary.
N/A	=	Not applicable
SLHDPE	=	Smooth lined high density polyethylene pipe;
PVC	=	Polyvinyl chloride;
RCP	=	Reinforced concrete pipe

Facility depth.

For the purposes of the design criteria, the facility depth is defined to be the depth between the bottom invert of the lowest orifice and the invert of the spillway. If there is no spillway, the top of the berm shall be used. For basins with no orifices or outlet structure, the bottom elevation of the basin shall be used.

Facilities with a facility depth greater than eight feet shall not be permitted in residential areas.

Facilities with a facility depth greater than 15 feet require a dam permit from DEP.

Embankment construction.

Impervious core/key trench. An impervious core/key trench, when required, shall consist of a cutoff trench (below existing grade) and a core trench (above existing grade). A key trench may not be required wherever it can be shown that another design feature, such as the use of an impermeable liner, accomplishes the same purpose.

Materials. Materials used for the core shall conform to the Unified Soil Classification GC, SC, CH, or CL and must have at least 30% passing the No. 200 sieve. Brecknock Township may require an impermeable liner to be installed up to the one-hundred-year design water surface elevation.

Dimensions.

[a]

The dimensions of the core shall provide a minimum trench depth of two feet below existing grade, minimum width of four feet and side slope of 1H:1V or flatter.

[b]

The core should extend up both abutments to the twenty-five-year water surface elevation or six inches below the emergency spillway elevation, whichever is lower.

[c]

The core shall extend four feet below any pipe penetrations through the impervious core. The core shall be installed along or parallel to the centerline of the embankment.

[3]

Compaction.

[a]

Compaction requirements shall be the same as those for the embankment to assure maximum density and minimum permeability.

[b]

The core shall be constructed concurrently with the outer shell of the embankment.

[c]

The trench shall be dewatered during backfilling and compaction operations.

Pipe collars. All pipe collars, when required, shall be designed in accordance with Chapter 7 of the DEP E&S Manual, as amended. The material shall consist of concrete or otherwise nondegradable material around the outfall barrel and shall be watertight. Design calculations shall be provided.

Embankment fill material. The embankment fill material shall be taken from an appropriate borrow area which shall be free of roots, stumps, wood, rubbish, stones greater than six inches, frozen or other objectionable materials.

Embankment compaction. When required, embankments shall be compacted by sheepsfoot or pad roller. The loose lift thickness shall be nine inches or less, depending on roller size, and the maximum particle size is six inches or less (two-thirds of the lift thickness). Five passes of the compaction equipment over the entire surface of each lift is required. Embankment compaction to visible nonmovement is also required.

Internal construction.

Bottom slope. The minimum bottom slope of facilities not designed for infiltration shall be 2%. A flatter slope may be used if an equivalent dewatering mechanism is provided.

Dewatering features. When required, dewatering shall be provided through the use of underdrain, surface device, or alternate approved by the Township Engineer. If the facility is to be used for infiltration, the dewatering device should be capable of being disconnected and only be made operational if the basin is not dewatering within the required timeframe.

Pretreatment elements. When required, pretreatment elements shall consist of forebays, or alternate approved by the Township Engineer, to keep silt to a smaller portion of the facility for ease of maintenance.

Infiltration basins. Within basins designed for infiltration, existing native vegetation shall be preserved, if possible. For existing unvegetated areas or for infiltration basins that require excavation, a planting plan shall be prepared in accordance with § 93-14G and the BMP Manual which is designed to promote infiltration.

Basin inlet and outlet structures should be located at maximum distances from one another. Brecknock Township may require a rock filter berm or rock-filled gabions between inlet and outlet areas when the distance is deemed insufficient for sediment trappings.

Outlet configuration.

For facilities with a depth of two feet or greater, a type D-W endwall or riser box outlet structure shall be provided.

For facilities with a depth less than two feet, no outlet structure is required.

All discharge control devices with appurtenances shall be made of reinforced concrete and stainless steel. Bolts/fasteners shall be stainless steel.

Spillway.

Material. The spillway shall be designed to provide a nonerosive, stable condition when the project is completed.

Nonemergency use. Use of the spillway to convey flows greater than the fifty-year design storm is permitted.

Emergency use. The spillway shall be designed to convey the one-hundred-year peak inflow assuming a blocked outlet structure.

When required, freeboard shall be measured from the top of the water surface elevation for emergency use.

Permanent grasses or stabilization measures shall be established on the sides of all earthen basins by seeding and mulching or hydroseeding within five days of initial construction (or conversion from sediment basin or sediment trap). Brecknock Township may require jute or erosion control matting to be installed inside the basin or on the basin embankment.

(9)

Stormwater runoff shall discharge to a suitable natural drainage course (except where prohibited by riparian buffer area regulations of this chapter and the Zoning Ordinance) or storm sewer system. Where not possible or not permitted, level-spreading devices or other suitable facilities (i.e., swale) shall be designed with sufficient capacity to convey the one-hundred-year storm event without creating any safety, flooding, or property hazard. Securing of necessary drainage easements for this purpose shall be the sole responsibility of the developer.

(10)

Breach analysis. The Township may require a breach analysis based on site-specific conditions and concern of threat for downstream property. When required, the breach analysis shall be conducted in accordance with the NRCS methodology, the US Army Corps of Engineers methodology (HEC-1) or other methodologies as approved by the Township.

(11)

Brecknock Township may require soil samples from the site to be analyzed to determine if these soils are suitable for berm embankment construction. If in the opinion of Brecknock Township the soils are found to be unsuitable, the developer shall import suitable soils for constructing the basin.

Subsurface storage facilities. Subsurface storage facilities consist of all stormwater facilities which store, infiltrate/evaporate/transpire, clean or otherwise affect stormwater runoff and the top of which is not exposed to the natural environment. Subsurface facilities are located below the finished ground elevation. Subsurface facilities do not include stormwater management facilities designed for conveyance.

Design criteria. Subsurface storage facilities shall comply with the design criteria in the following table:

Subsurface storage facility design criteria
		Facility Type
		Infiltration and storage	Storage without infiltration
(a)	Facility Geometry
[1]	Depth from surface (maximum)	2 feet less than limiting zone	N/A
[2]	Loading ratio (maximum)	Per BMP Manual*	N/A
(b)	Distribution System Requirements
[1]	Pipe size (minimum)	4 inches	4 inches
[2]	Pretreatment	Required	Required
[3]	Loading/balancing	Required	Not required
[4]	Observation/access ports	Required	Required
[5]	Overflow system	Required	Required

Unless otherwise determined by professional geologic evaluation.

Distribution system requirements.

Pretreatment requirements. The facility shall be designed to provide a method to eliminate solids, sediment, and other debris from entering the subsurface facility.

Loading/balancing. The facility shall be designed to provide a means of evenly balancing the flow across the surface of the facility to be used for infiltration.

Observation/access ports.

For facilities with the bottom less than five feet below the average grade of the ground surface, a clean-out shall be an acceptable observation port.

For facilities with the bottom five feet or more below the average grade of the ground surface, a manhole or other means acceptable to the Township shall be provided for access to and monitoring of the facility.

[3]

The number of access points shall be sufficient to flush or otherwise clean out the system.

Materials.

Pipe material. Distribution system piping may be PVC, SLHDPE, or RCP.

Stone for infiltration beds. The stone used for infiltration beds shall be clean washed, uniformly graded coarse aggregate (AASHTO No. 3 or equivalent approved by the Township). The void ratio for design shall be assumed to be 0.4.

Backfill material. Material consistency and placement depths for backfill shall be (at a minimum) per all applicable pipe manufacturer's recommendations, further providing it should be free of large (not exceeding six inches in any dimension) objectionable or detritus material. Select nonaggregate material should be indigenous to the surrounding soil material for nonvehicular areas. Backfill within vehicular areas shall comply with this section unless otherwise specified in governing municipal road/street or subdivision and land development ordinances. Furthermore, if the design concept includes the migration of runoff through the backfill to reach the infiltration facility, the material shall be well drained, free of excess clay or clay-like materials and generally uniform in gradation.

Lining material. Nonwoven geotextiles shall be placed on the sides and top of subsurface infiltration facilities. No geotextiles shall be placed on the bottom of subsurface infiltration facilities.

Cover.

When located under pavement, the top of the subsurface facility shall be a minimum of three inches below the bottom of pavement subbase.

Where located under vegetative cover, the top of the subsurface facility shall be a minimum of 12 inches below the surface elevation or as required to establish vegetation.

In all cases, subsurface facilities shall be designed to safely convey and/or bypass flows from storms exceeding the design storm. An overflow system shall be provided to accommodate flows in excess of design criteria and divert flows to appropriate areas of discharge without damage to property. Design of the overflow system shall be approved by the Municipal Engineer.

Conveyance facilities. Conveyance facilities consist of all stormwater facilities which carry flow, which may be located either above or below the finished grade. Conveyance facilities do not include stormwater management facilities which store, infiltrate/evaporate/transpire, or clean stormwater runoff.

Design criteria. Conveyance facilities shall comply with the design criteria in the following table:

Conveyance facility design criteria
Location		Within public street right-of-way	Outside public street right-of-way
Loading		All	Vehicular loading	Non-vehicular loading
(a)	Pipe design
[1]	Material	SLHDPE, RCP	SLHDPE, RCP	SLHDPE, RCP
[2]	Slope (minimum)	0.5%	0.5%	0.5%
[3]	Cover	1 foot to stone subgrade	1 foot to stone subgrade	1 foot to surface
[4]	Diameter (minimum)	15 inches	15 inches	12 inches
[5]	Street crossing angle	75° to 90°	N/A	N/A
[6]	Access/ maintenance port frequency (maximum)	300 feet	300 feet	300 feet
(b)	Inlet design
[1]	Material	Concrete	Concrete	N/A
[2]	Grate depression	2 inches	2 inches	1 inch minimum
(c)	Manhole design
[1]	Material	Concrete	Concrete	Concrete
(d)	Swale design
[1]	Freeboard (minimum)	6 inches	N/A	6 inches
[2]	Velocity (maximum)	Stability check	N/A	Stability check
[3]	Slope (minimum)	2%	N/A	2%
[4]	Side slopes (residential area)	4:1 max	N/A	4:1 max
[5]	Side slopes (non-residential area)	4:1 max	N/A	3:1 max
[6]	Bottom width to flow depth ratio	12:1	N/A	12:1
(e)	Outlet design
[1]	End treatment	Headwall/ endwall	N/A	Headwall/ endwall or flared end section
[2]	Energy dissipater	Required	N/A	Required

N/A	=	Not applicable or no criteria specified
SLHDPE	=	Smooth lined high density polyethylene pipe; PVC = Polyvinyl chloride;
RCP	=	Reinforced concrete pipe

All stormwater conveyance facilities (excluding detention, retention, and wetland basin outfall structures) shall be designed to convey a twenty-five-year storm event. All stormwater conveyance facilities (excluding detention, retention, and wetland basin outfall structures) conveying water originating from offsite shall be designed to convey a fifty-year storm event. Safe conveyance of the one-hundred-year runoff event, including the effects of the control facility tailwater, to appropriate peak rate control BMPs must be demonstrated in the design through storm sewer capacity, or where approved by Brecknock Township, overflow swales. All storm events shall be based on a twenty-four-hour SCS Type II storm or an IDF Curve Rational Method storm.

All conveyance pipes, culverts, manholes, inlets and endwalls shall be constructed per PennDOT specifications as outlined in Publication 408; Design Manual Part 2, Standards for Roadway Construction, Publication No. 72M. Conveyance pipes, culverts, manholes, inlets and endwalls which are subject to vehicular loading shall be designed for the HS-25 loading condition.

Conveyance pipes.

Backfill and bedding requirements. Material consistency and placement depths for backfill shall be (at a minimum) per all applicable pipe manufacturer's recommendations, further providing it should be free of large (not exceeding six inches in any dimension) objectionable or detritus material. Select nonaggregate material should be indigenous to the surrounding soil material for nonvehicular areas. All storm sewer within the public right-of-way and/or beneath a paved surface shall be bedded and backfilled with PennDOT 2A stone. This backfill shall be placed at a minimum in six-inch lifts and solidly compacted to the satisfaction of Brecknock Township.

Inlets or manholes shall be placed at all points of changes in the horizontal or vertical directions of conveyance pipes. Curved pipe sections are prohibited.

Access/maintenance ports. An access/maintenance port is required may either be an inlet or manhole.

All storm sewers within the streets shall not be placed under the curbs or sidewalks.

The street crossing angle shall be measured between the pipe centerline and the street centerline.

Watertight joints shall be provided where pipe sections are joined, except for perforated pipe installed as pavement base drain, and appropriate specifications listed on the plans. The watertight joints shall meet the ASTM laboratory pressure of 10.8 psi per ASTM D-3212. The joints shall prevent the infiltration of soil and the exfiltration of stormwater.

(g)

Elliptical pipe of an equivalent cross-sectional area may be substituted in lieu of circular pipe where cover or utility conflict conditions exist.

(h)

The roughness coefficient (Manning "n" values) used for conveyance pipe capacity calculations should be determined in accordance with Appendix B-4.

(i)

Any storm sewer pipe which outlets on private residential property may only discharge to the rear yard and must be a minimum of 50 feet beyond habitable structures.

Inlets, junction boxes and manholes.

When there is a change in pipe size through an inlet, the top inside elevation of the outlet shall be at or below the top inside elevations of all incoming pipes (i.e., match crowns).

All pipes must enter inlets completely through one of the sides. No corner entry of pipes is permitted.

Storm sewer design shall be based upon PennDOT design methods. Inlet efficiency and bypass flow for the one-hundred-year storm shall be determined for all inlets and the gutter flow spread shall not exceed 1/2 the travel lane width, or to a maximum of eight feet where parking is permitted. Brecknock Township may require that a hydraulic grade line analysis be performed on storm sewer systems.

Flow depth within intersections. Within intersections of streets, the maximum depth of flow shall be 1 1/2 inches based on the one-hundred-year storm.

Curbed streets.

Inlets in streets shall be located along the curb line. At street intersections, inlets shall be placed in the tangent, and not in the curved portion of the curbing.

Top units shall be PennDOT Type C. The hood shall be aligned with the adjacent curb height.

All inlets placed in paved areas shall have heavy duty bicycle-safe grating consistent with PennDOT Publication 72M, latest edition. A note to this effect shall be added to the SWM site plan or inlet details therein.

(g)

Inlets, junction boxes, or manholes greater than five feet in depth shall be equipped with ladder rungs and shall be detailed on the SWM site plan.

(h)

PennDOT Type C precast concrete inlet tops are to be provided with a five-inch-by-twenty-four-inch cast iron "Dump No Waste — Drains to Waterway" (with one-half-inch raised lettering) plate with trout logo as manufactured by E. Jordan Iron Works or approved equal. Bottom of tops (grates) are to be clearly marked with grade of iron (ASTM A48, Class 35B), product number and date of manufacture. All other PennDOT inlets are to be provided with either a painted stenciled logo on the roadway or another acceptable marking approved by Brecknock Township.

(i)

The words "Dump No Waste — Drains to Waterway" in one-and-one-quarter-inch raised letters with bass logo shall be cast or stamped into the storm sewer manhole covers as manufactured by E. Jordan Iron Works or approved equal. Bottom of covers are to be clearly marked with grade of iron (ASTM A48, Class 35B), product number and date of manufacture.

(j)

When precast concrete inlets or manholes are used within a street, either solid one-piece or maximum two-piece "C" concrete adjustment units or rubber ring adjustment units (as manufactured by GNR or approved equal) shall be placed to bring the grate or cover to proper elevation. Bricks, concrete blocks or pieces of materials shall not be used. Epoxy grout, not mortar, shall be used to seal the joints between the top unit and the adjustment and the adjustment and the box or structure. The joints must be watertight in that the groundwater and soils shall not infiltrate into the structure and stormwater shall not exfiltrate the structure.

Swales.

A swale shall be considered as any man-made ditch designed to convey stormwater directly to another stormwater management facility or surface waters.

Inlets within swales shall have PennDOT Type M top units or equivalent approved by the Township engineer.

Swale capacities and velocities shall be computed using the Manning equation using the following design parameters:

Vegetated swales.

[a]

The first condition shall consider swale stability based upon a low degree of retardance ("n" = 0.03);

[b]

The second condition shall consider swale capacity based upon a higher degree of retardance ("n" = 0.05); and

[c]

All vegetated swales shall have a minimum slope of 2% unless otherwise approved by the Township Engineer.

The "n" factors to be used for paved or riprap swales or gutters shall be based upon accepted engineering design practices, as approved by the Township Engineer.

All swales shall be designed to maximize infiltration and concentrate low flows to minimize siltation and meandering, unless geotechnical conditions do not permit infiltration.

Adequate erosion protection and energy dissipation shall be provided along all swales and at all points of discharge. Design methods shall be consistent with the Federal Highway Administration Hydraulic Engineering Circular Number 11 (Publication No. FHWA-IP-89-016, as amended) and the DEP E&S Manual, or other design guidance acceptable to the Township Engineer.

Swales shall be stabilized with seed mixes and/or other plantings suitable for the underlying soil conditions and swale function (infiltration/conveyance only).

Level spreaders.

Shall discharge at existing grade onto undisturbed vegetation.

Discharge at a depth not exceeding 3.0 inches for a fifty-year, twenty-four-hour design storm.

Energy dissipaters. Energy dissipaters shall be designed in accordance with the requirements in the DEP E&S Manual and design calculations provided. Erosion protection shall be provided along all open channels, and at all points of swale or storm sewer discharge. Flow velocities from any storm sewer or swale may not result in erosion of the receiving channel.

(9)

End treatments.

Where the connecting pipe has a diameter 15 inches or greater, headwalls and endwalls shall be provided with a protective barrier device to prevent entry of the storm sewer pipe by unauthorized persons. Such protection devices shall be designed to be removable for cleaning.

Headwalls and endwalls shall be constructed of concrete and shall be set on a minimum of 12 inches of AASHTO No. 57 (PennDOT 2B) coarse aggregate.

Flared end sections shall be of the same material as the connecting pipe and be designed for the size of the connecting pipe and set on a minimum of 12 inches of AASHTO No. 57 (PennDOT 2B) coarse aggregate.

(10)

Easements.

Storm facilities not located within a public right-of-way shall be contained in and centered within an easement, a minimum 20 feet wide, or that width necessary to allow access for maintenance and convey all storms up to and including the one-hundred-year storm.

The easement shall provide for ingress/egress from a public right-of-way.

Easements shall follow property boundaries where possible.

A note on the plan shall indicate that the easement allows Brecknock Township the right, but not the responsibility, to perform needed maintenance and/or repairs and backcharge the owner or lien the property of the owner.

(11)

Existing stormwater conveyance facilities. Existing culverts, swales and other similar facilities within the public right-of-way and along the frontage of the proposed development shall be analyzed for their capacity based on the predevelopment runoff from the twenty-five-year storm to determine the need for future improvements by Brecknock Township or others.

Roof drains.

Stormwater roof drains shall not discharge water into any sanitary sewer line.

Except for single-family homes, proposed roof drains and collector locations shall be shown on the storm drainage plans. Roof drains and collectors shall meet all appropriate Brecknock Township Code.

Roof drains and sump pumps shall be tributary to infiltration or vegetative BMPs. Use of catchment facilities for the purpose of reuse may be permitted with the approval of the Township Engineer.

Roof drains shall not be connected to sanitary sewers. Wherever possible, roof drains should not be connected to storm sewers or roadside ditches.

Design of bridges and culverts.

Bridges and culverts shall have ample waterway to carry the design flows, based on a minimum storm frequency of 25 years, unless a larger design flow is required by PA DEP. One-hundred-year water depths shall not exceed six inches above the roadway center line elevation. Bridge and/or culvert construction shall be in accordance with the PA DOT specifications and shall meet the requirements of the PA DEP. The appropriate permits and approvals must be acquired by the applicant prior to final plan approval.

Culverts under roadways shall be provided with wing walls and constructed for the full width of the right-of-way. Easements shall be provided for maintenance.

Culverts not in roadways shall be provided with wing walls and extra-wide easements shall be provided for access and maintenance.

If Brecknock Township determines that the character of the road is expected to change for future planning, the cartway of the bridge shall be made to anticipate this condition. On each side of the bridge cartway, the bridge railing must be set back from the edge of the final cartway and this area may be used to place sidewalks, bike trails, etc. Easements shall be provided for maintenance.

Culverts shall meet the applicable material requirements outlined in to § 93-14C. In addition to the material requirements in this section, culverts designed to convey waters of the commonwealth may be constructed with either a corrugated metal arch or a precast concrete culvert.

Dams. SWM facilities which qualify as a dam per DEP regulations or facilities deemed a potential threat to the life, safety or welfare of the general public shall be subject to the following requirements:

Facilities which qualify as a dam per DEP regulation shall obtain the required permit through DEP and design the facility in accordance with DEP standards.

Additional requirements and analysis may be required by the Township to prove that the proposed facility has been designed to limit the potential risk to the life, safety or welfare of the general public.

Planting plan. A planting plan is required for all vegetated stormwater BMPs.

Native or naturalized/noninvasive vegetation suitable to the soil and hydrologic conditions of the development site shall be used unless otherwise specified in the BMP manual.

Invasive vegetation may not be included in any planting schedule. [See Invasive Plants in Pennsylvania by the Department of Conservation and Natural Resources (DCNR).]

All areas of aboveground stormwater management facilities, including basin floors, side slopes, berms, impoundment structures, etc., shall be planted with suitable vegetation such as naturalized meadow plantings or lawn grass specifically suited for the permanently wet, intermittently wet and usually dry areas of the stormwater facilities.

The limit of existing, native vegetation to remain shall be delineated on the plan along with proposed construction protection measures.

Prior to construction, a tree protection zone shall be delineated at the dripline of the tree canopy. All trees scheduled to remain during construction shall be marked; however, where groups of trees exist, only the tress on the outside edge need to be marked. A forty-eight-inch-high snow fence or forty-eight-inch-high construction fence mounted on steel posts located eight feet on center shall be placed along the tree protection boundary. No construction, storage of material, temporary parking, pollution of soil, or regrading shall occur within the tree protection zone.

All planting shall be performed in conformance with good nursery and landscape practice. Plant materials shall conform to the standards recommended by the American Association of Nurseryman, Inc., in the American Standard of Nursery Stock.

Planting designs are encouraged to share planting space for optimal root growth whenever possible.

No staking or wiring of trees shall be allowed without a maintenance note for the stake and/or wire removal within one year of planting.

§ 93-15 Calculation methodology.

Stormwater runoff from all development sites shall be calculated using either the modified rational method, a soil-cover-complex methodology, or other method acceptable to Brecknock Township.

Any stormwater runoff calculations involving drainage areas generally greater than 20 acres and Tc greater than 60 minutes, including on- and off-site areas, shall use generally accepted calculation technique that is based on the NRCS soil cover complex method. Table VIII-1 summarizes acceptable computation methods. It is assumed that all methods will be selected by the design professional based on the individual limitations and suitability of each method for a particular development site.

[Amended 4-8-2014 by Ord. No. 198-2014]

TABLE III-1
Acceptable Computation Methodologies for Stormwater Management Plans
Method	Method Developed By	Applicability
TR-20 (or commercial computer package based on TR-20)	USDA NRCS	Applicable where use of full hydrology computer model is desirable or necessary
TR-55 (or commercial computer package based on TR-55)	USDA NRCS	Applicable for land development plans within limitations described in TR-55
HEC-1/HEC-HMS	US Army Corps of Engineers	Applicable where use of full hydrologic computer model is desirable or necessary
Rational Method (or commercial computer package based on Rational Method)*	Emil Kuichling (1889)	For development sites less than 20 acres, Tc less than 60 minutes or as approved by Brecknock Township
Other methods	Varies	Other methodologies approved by the municipal designee
* Use of the Rational Method to estimate peak discharges from drainage areas that contain more than 20 acres must be approved by the Brecknock Township Engineer. The Rational Method shall not be used to satisfy the requirements of § 93-15F. Without the consent of the Brecknock Township Engineer.

Calculation by methods.

If the Soil-Cover-Complex Method is used, stormwater runoff shall be based on the following twenty-four-hour storm events published in "Urban Hydrology for Small Watersheds," by USDA NRCS Engineering Division, also known as TR55. The original source was the U.S. Department of Commerce, Weather Bureau Technical Paper No. 40 (TP-40), "Rainfall Frequency Atlas of the United States," May 1961.

	Storm Event	Inches of Rainfall
	2 years	3.1
	5 years	4.1
	10 years	5.0
	25 years	5.5
	50 years	6.2
	100 years	7.0

If the NRCS method is used, antecedent moisture condition 1 is to be used in areas of carbonate geology, and antecedent moisture condition 2 is to be used in all other areas. A Type II distribution shall be used in all areas.

[Amended 4-8-2014 by Ord. No. 198-2014]

If the Rational Method is used, the National Oceanic and Atmospheric Administration (NOAA) Atlas 14 data or PennDOT Publication 584 "PennDOT Drainage Manual," 2008 Edition, or latest, shall be used to determine the rainfall intensity in inches per hour based on the information for the five- through sixty-minute duration storm events.

[Amended 4-8-2014 by Ord. No. 198-2014]

Hydrographs may be obtained from NRCS methods such as TR-55, TR20, or from use of the "modified" or "unit hydrograph" rational methods. If "modified" or "unit hydrograph" rational methods are used, the ascending leg of the hydrograph shall have a length equal to three times the time of concentration (3xTc) and the descending leg shall have a length equal to seven times the time of concentration (7xTc) to approximate an SCS Type II hydrograph.

[Added 4-8-2014 by Ord. No. 198-2014]

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 predevelopment and postdevelopment rates for peak discharge of stormwater runoff from the development site.

For the purpose of calculating predevelopment peak discharges, all runoff coefficients, both on-site and off-site, shall be based on actual land use assuming summer or good land conditions. Runoff coefficients for off-site discharges used to design facilities shall be based on actual land use assuming winter or poor land conditions.

Criteria and assumptions to be used in the determination of stormwater runoff and design of management facilities are as follows:

Runoff coefficients shall be based on the information contained in Appendixes B-2 and B-3[1] if the actual land use is listed in those Appendixes. If the actual land use is not listed in these Appendixes, runoff coefficients shall be chosen from other published documentation, and a copy of said documentation shall be submitted with the stormwater management report.

Editor's Note: Appendixes B-2 and B-3 are included at the end of this chapter.

Times of concentration shall be based on the following design parameters:

Sheet flow: The maximum length for each reach of sheet or overland flow before shallow concentrated or open channel flow develops is 150 feet. Flow lengths greater than 100 feet shall be justified based on the actual conditions at each development site.

Shallow concentrated flow: Travel time for shallow concentrated flow shall be determined using Figure 3-1 from TR-55, Urban Hydrology for Small Watersheds.

Open channel flows: At points where sheet and shallow concentrated flows concentrate in field depressions, swales, gutters, curbs, or pipe collection systems, the travel times and downstream end of the development site between these design points shall be based upon Manning's equation and/or acceptable engineering design standards as determined by the Municipal Engineer.

Volume control BMPs are intended to maintain existing hydrologic conditions for small storm events by promoting groundwater recharge and/or evapotranspiration as described in this section. The green infrastructure and low impact development practices provided in the BMP Manual shall be utilized for all regulated activities wherever possible. Runoff volume controls shall be designed using the Design Storm Method described in Subsection F(1) below. Small projects may use the method described in Subsection F(2) to design volume control BMPs.

[Amended 4-8-2014 by Ord. No. 198-2014; 11-8-2022 by Ord. No. 231-2022]

The Design Storm Method is applicable to any size of regulated activity and requires detailed modeling based on site conditions.

Do not increase the post-development total runoff volume for all storms equal to or less than the two-year twenty-four-hour storm event.

For modeling purposes, existing (predevelopment) nonforested pervious areas must be considered meadow in good condition. When the existing project site contains impervious area, 20% of existing impervious area to be disturbed shall be considered meadow in good condition in the model for existing conditions.

Volume control for small projects. At least the first one inch of runoff from new impervious surfaces or an equivalent volume shall be permanently removed from the runoff flow. Removal options include reuse (maximum 50% of the volume), evaporation, transpiration and infiltration, subject to approval by the Township Engineer.

Infiltration BMPs intended to receive runoff from developed areas shall be selected based on suitability of soils and development site conditions and shall be constructed on soils that have the following characteristics:

A minimum depth of 24 inches between the bottom of the facility and the limiting zone, unless it is demonstrated to the satisfaction of the Township that the selected BMP has design criteria which allow for a smaller separation.

A stabilized infiltration rate sufficient to accept the additional stormwater load and drain completely as determined by field tests conducted by the applicant's professional designer.

The stabilized infiltration rate is to be determined in the same location and within the same soil horizon as the bottom of the infiltration facility.

The stabilized infiltration rate is to be determined as specified in the BMP Manual.

Be set back at least 25 feet from all buildings and features with subgrade elements (e.g., basements, foundation walls, etc.), unless otherwise approved by the Township Engineer;

For any infiltration practice that collects runoff from shared or multiple features and that is located within 25 feet of a building or feature with subgrade elements (e.g., basements, foundation walls, etc.), the bottom elevation shall be set below the elevation of the subgrade element.

The recharge volume provided at the development site shall be directed to the most permeable HSG available.

Infiltration BMPs shall be spread out, 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. Infiltration BMPs shall include pretreatment BMPs unless shown to be unnecessary.

Storage facilities, including normally dry, open top facilities, shall completely drain the volume control storage over a period of time not less than 24 hours and not more than 72 hours from the end of the design storm. 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, provided that none of this water will be discharged into waters of this commonwealth.

The groundwater recharge volume shall be infiltrated within 48 hours after the end of the design storm.

Development sites where the postdeveloped impervious area is equal to or less than the predeveloped impervious area shall not be required to provide groundwater recharge volume.

Calculation of water quality volume: The water quality volume (WQ_v) is the storage capacity needed to treat stormwater runoff equivalent to a minimum of the first 1.2 inches of runoff from the developed areas of the development site.

The following calculation is used to determine the storage volume, WQ_v in acre-feet of storage:

WQ_v	=	[(1.2) (R_v)(A)]/12
WQ_v	=	Water quality volume in acre-feet
A	=	Area of watershed in acres
R_v	=	0.05 + 0.9(I) where I = net increase in impervious area/area of watershed (A)

WQ_v shall be designed as part of a stormwater management facility which incorporates water quality BMPs as a primary benefit of using that facility, in accordance with design specifications contained in Pennsylvania Handbook of Best Management Practices for Developing Areas, 1998. The water quality volume shall take a minimum of 24 hours to be discharged from the basin. Development sites where the postdeveloped impervious area is equal to or less than the predeveloped impervious area shall not be required to provide water quality volume, unless required by NPDES Part II.

§ 93-16 Use of performance standards and criteria.

The methodology for determining required stormwater controls for a regulated activity is shown in Table III-1 in § 93-15 and is outlined below.

Compute:

Predevelopment hydrograph at the development site discharge point for the required design storm.

Postdevelopment hydrograph at the development site discharge point incorporating best management practices such as groundwater recharge volume and water quality volume, previous areas, grass swales, infiltration trenches, etc.

Note: Hydrographs may be obtained from NRCS methods such as TR-55, TR20, or from use of the modified or unit hydrograph rational methods.

Compare: Postdevelopment hydrographs with predevelopment hydrographs. If the peak rate of runoff does not exceed the predevelopment runoff at all points in time, stormwater management has been achieved. Detention will not be required. If not, proceed to Subsection C.

Design: Detention/retention facilities, in conjunction with any nondetention techniques, such that postdevelopment peak rates from the development site will not exceed permissible levels for required design storms.


Stormwater Control Determination Flow Chart

§ 93-17 Various other site development requirements.

Procedures for protecting soils or geologic structures with water supply potential from contamination by surface water or other disruption by construction activity shall be established in consultation with Brecknock Township and such areas shall include, at minimum, those underlain by carbonate limestone formations. Brecknock Township may require pollution control facilities to be provided on existing or proposed stormwater management systems within or adjacent to the project site.

Provisions for protecting existing wells or other water supplies shall be established.

Any graded slopes shall not be steeper than three horizontal units to one vertical unit.

A minimum of six inches of topsoil shall be provided on all disturbed areas prior to final seeding and mulching.

Mature healthy trees of at least six inches diameter at breast height (DBH) and other significant existing vegetation within the limits of earth disturbance shall be located in the field and on the storm drainage plan and shall be retained and protected. Such trees shall not be removed except as provided on the approved subdivision or land development plan. The filling of soil over the roots of trees to be preserved is prohibited. Roots are presumed to extend out from the tree as far as the tree's branches extend outward.

All existing and natural watercourses, channels, drainage systems, wetlands and areas of surface water concentration shall be maintained in their existing condition unless an alteration is approved by Brecknock Township and any other necessary approving body.

§ 93-17.1 Floodplain management requirements.

[Added 4-9-2013 by Ord. No. 187-2013; 3-8-2016 by Ord. No. 210-2016]

Floodplain areas shall be established and preserved as required by the Brecknock Township Zoning Ordinance, § 110-26, and the Brecknock Township Floodplain Management Ordinance, Chapter 93.

Whenever a floodplain area is located within or along a lot, the record plan (where a regulated activity constitutes a subdivision or land development) or stormwater management site plan (where a regulated activity does not constitute a subdivision or land development) shall include:

All plan information and dimensions as required by the Brecknock Township Floodplain Management Ordinance, Chapter 93.

A plan note that the floodplain area shall be kept free of structures, fill, and other encroachments, except as permitted by the Brecknock Township Zoning Ordinance, § 110-26, and the Brecknock Township Floodplain Management Ordinance, Chapter 93.

A plan note that floor elevations for all structures adjacent to the floodplain area shall be in compliance with the Brecknock Township Zoning Ordinance, § 110-48, and the Brecknock Township Floodplain Management Ordinance, Chapter 93.

§ 93-18 Erosion and sedimentation requirements.

Whenever the vegetation and topography are to be disturbed, such activity must be in conformance with Chapter 102, Title 25, Rules and Regulations, Part I, Commonwealth of Pennsylvania, Department of Environmental Protection, Subpart C, Protection of Natural Resources, Article II, Water Resources, Chapter 102, "Erosion Control," and in accordance with the Lancaster County Conservation District.

Additional erosion and sedimentation control design standards and criteria that must be applied where infiltration BMPs are proposed shall include the following:

Areas proposed for infiltration BMPs shall be protected from sedimentation and compaction during the construction phase, so as to maintain their maximum infiltration capacity.