ARTICLE 925

STORMWATER MANAGEMENT REGULATIONS

SECTION 1
GENERAL PROVISIONS

925.01 SHORT TITLE

This Ordinance shall be known and may be cited as the “City of Bethlehem Stormwater Management Ordinance”.
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925.02 STATEMENT OF FINDINGS

The governing body of the municipality finds that:

A. Inadequate management of accelerated runoff of stormwater resulting from development throughout a watershed increases flood flows and velocities, contributes to erosion and sedimentation, changes the natural hydrologic patterns, destroys aquatic habitat, elevates aquatic pollutant concentrations and loadings, overtaxes the carrying capacity of streams and storm sewers, greatly increases the cost of public facilities to carry and control stormwater, undermines floodplain management and flood control efforts in downstream communities, reduces groundwater recharge, and threatens public health and safety.

B. A comprehensive program of stormwater management, including reasonable regulation of development and activities causing accelerated erosion and loss of natural infiltration, is fundamental to the public health, safety and welfare and the protection of the people of the municipality and all the people of the Commonwealth, their resources and the environment.

C. Stormwater can be an important resource by providing groundwater recharge for water supplies and baseflow of streams, which also protects and maintains surface water quality.

D. Public education on the control of pollution from stormwater is an essential component in successfully addressing stormwater.

E. Federal and state regulations require certain municipalities to implement a program of stormwater controls. These municipalities are required to obtain a permit for stormwater discharges from their separate storm sewer systems under the National Pollutant Discharge Elimination System (NPDES).

F. Non-stormwater discharges to municipal separate storm sewer systems can contribute to pollution of waters of the Commonwealth by the municipality.

925.03 PURPOSE

The purpose of this Ordinance is to promote the public health, safety and welfare within the City’s Watersheds by minimizing the damages and maximizing the benefits described in Section 925.02 of this Ordinance by provisions designed to:

A. Manage stormwater runoff impacts at their source by regulating activities which cause such problems.

B. Utilize and preserve the desirable existing natural drainage systems.

C. Encourage infiltration of stormwater, where appropriate, to maintain groundwater recharge, to prevent degradation of surface and groundwater quality and to otherwise protect water resources.

D. Maintain the existing flows and quality of streams and watercourses in the municipality and the Commonwealth.

E. Preserve and restore the flood carrying capacity of streams.

F. Provide for proper maintenance of all permanent stormwater management BMPs that are implemented in the City.

G. Provide review procedures and performance standards for stormwater planning, design and management.

H. Manage stormwater impacts close to the runoff source which requires a minimum of structures and relies on natural processes.

I. Meet legal water quality requirements under state law, including regulations at 25 Pa. Code Chapter 93.4a to protect and maintain “existing uses” and maintain the level of water quality to support those uses in all streams and to protect and maintain water quality in “special protection” streams.

J. Prevent scour and erosion of streambanks and streambeds.

K. Provide standards to meet the NPDES permit requirements.

925.04 STATUTORY AUTHORITY

The City is empowered to regulate these activities by the authority of the Act of October 4, 1978, P.L. 864 (Act 167), 32 P.S. Section 680.1, et seq., as amended, the “Stormwater Management Act” and the “Pennsylvania Municipalities Planning Code”, 53. P.S. Section 10101, et seq.

925.05 APPLICABILITY

This Ordinance shall apply to those areas of the City which are located within the Catasauqua Creek & Lehigh River Sub-Basin, Monocacy Creek, Nancy Run and Saucon Creek Watersheds as delineated on the official maps available for inspection at the City, Engineering Bureau.

The following activities are defined as Regulated Activities and shall be regulated by this Ordinance:

A. Land development.

B. Subdivision.

C. Construction of new or additional impervious surfaces (driveways, parking lots, etc.).

D. Construction of new buildings or additions to existing buildings, including residential construction.

E. Earth moving

F. Agricultural Operations

G. Forest Management Operations

H. Nursery Operations

I. Diversion or piping of any natural or man-made stream channel.

J. Installation of stormwater systems or appurtenances thereto.

K. Regulated Earth Disturbance Activities.

925.06 EXEMPTIONS

A. Impervious Cover - Any proposed Regulated Activity, except those defined in Section 925.05I and 925.05J, which would create 10,000 square feet or less of additional impervious cover is exempt from the Drainage Plan preparation provisions of this Ordinance except as cited in Section 925.06C and D. The date of the City Ordinance adoption of the original Act 167 Stormwater Management Ordinances (1988) shall be the starting point from which to consider tracts as “parent tracts” in which future subdivisions and respective impervious area computations shall be cumulatively considered. For development taking place in stages, the entire development plan must be used in determining conformance with this criteria. Additional impervious cover shall include, but not be limited to, any roof, parking or driveway areas and any new streets and sidewalks constructed as part of or for the proposed Regulated Activity. Any additional areas proposed to initially be gravel, crushed stone, porous pavement, etc. shall be assumed to be impervious for the purposes of comparison to the exemption criteria. Any existing gravel, crushed stone or hard packed soil areas on a site shall be considered as pervious cover for the purpose of exemption evaluation. All of the impervious cover added incrementally to a site above the initial 10,000 square feet shall be subject to the provisions of this Ordinance. If a site has previously received an exemption and is proposing additional development such that the total impervious cover on the site exceeds 10,000 square feet, the total impervious cover on the site proposed since the original ordinance date must meet the provisions of this Ordinance.

B. Prior Drainage Plan Approval - Any Regulated Activity for which a Drainage Plan was previously prepared as part of a subdivision or land development proposal that received preliminary plan approval from the municipality prior to the effective date of this Ordinance is exempt from the water quantity provisions of this Ordinance, except as cited in Section 925.06C, provided that the approved Drainage Plan included design of stormwater facilities to control runoff from the site currently proposed for development consistent with ordinance provisions in effect at the time of approval and the approval has not lapsed under the Municipalities Planning Code. If significant revisions are made to the Drainage Plan after both the preliminary plan approval and the effective date of this Ordinance, preparation of a new Drainage Plan, subject to the provisions of this Ordinance, shall be required. Significant revisions would include a change in control methods or techniques, relocation or redesign of control measures or changes necessary because soil or other conditions are not as stated on the original Drainage Plan.

C. These exemptions shall not relieve the applicant from implementing such measures as are necessary to protect health, safety and property. These measures include adequate and safe conveyance of stormwater on the site and as it leaves the site. These exemptions shall not relieve the applicant from meeting the water quality standards in this Ordinance for all development proposed since the municipal adoption date of this Ordinance.

D. Any regulated activity that meets the exemption criteria in Section 925.06A or B, in lieu of meeting the water quality criteria in Section 925.15, will be consistent with the Ordinance if one of the BMPs listed below is employed on the site to control water quality.

1. Controlling runoff through a “sheet flow” system of vegetative or similar buffers having a minimum flow length equal to the length of the impervious areas.
2. Disconnecting roof downspouts from direct discharge to curb/gutter or storm sewer systems and allowing the downspout discharge to flow over plant, lawn or woodland areas in such a manner as to avoid rill or gully erosion.
3. Infiltration designed to meet the provisions of this Ordinance.
4. Employing any one of the BMPs listed in Section 304.O.

Sites that meet the exemption criteria in Section 925.06A or B are not required to conduct a Preliminary Site Investigation (as defined in Section 925.11) as long as infiltration BMPs are not proposed. If infiltration BMPs are proposed, a Preliminary Site Investigation shall be performed. The City shall have the authority to require, review, approve, reject or recommend alternative methods for meeting the water quality requirements of this Ordinance.

E. No exemptions shall be provided for regulated activities as defined in Sections 925.05I and 925.05J.

925.07 REPEALER

Any ordinance of the City inconsistent with any of the provisions of this Ordinance is hereby repealed to the extent of the inconsistency only.

925.08 SEVERABILITY

Should any section or provision of this Ordinance be declared invalid by a court of competent jurisdiction, such decision shall not affect the validity of any of the remaining provisions of this Ordinance.

925.09 COMPATIBILITY WITH OTHER ORDINANCE REQUIREMENTS

Approvals issued pursuant to this Ordinance do not relieve the applicant of the responsibility to secure required permits or approvals for activities regulated by any other applicable code, rule, act or ordinance.

925.10 DUTY OF PERSONS ENGAGED IN THE DEVELOPMENT OF LAND

Notwithstanding any provisions of this Ordinance, including exemption and waiver provisions, any landowner and any person engaged in the alteration or development of land which may affect stormwater runoff characteristics shall implement such measures as are reasonably necessary to prevent injury to health, safety or other property. Such measures shall include such actions as are required to manage the rate, volume, direction and quality of resulting stormwater runoff in a manner which otherwise adequately protects health and property from possible injury.

925.11 DEFINITIONS

For the purposes of this Ordinance, certain terms and words used herein shall be interpreted as follows:

A. Words used in the present tense include the future tense; the singular number includes the plural, and the plural number includes the singular; words of masculine gender include feminine gender; and words of feminine gender include masculine gender.
B. The word “includes” or “including” shall not limit the term to the specific example but is intended to extend its meaning to all other instances of like kind and character.

C. The words “shall” and “must” are mandatory; the words “may” and “should” are permissive.

Accelerated Erosion – The removal of the surface of the land through the combined action of human activities and natural processes, at a rate greater than would occur because of the natural process alone.

Act 167 – Act of October 4, 1978, P.L. 864, the “Stormwater Management Act.”

Act 247 – Act of 1968, P.L. 805, No. 247 “ Pennsylvania Municipalities Planning Code.”

Best Management Practice (BMP) – Activities, facilities, measures or procedures used to manage stormwater quantity and quality impacts from the regulated activities listed in Section 105, to meet State Water Quality Requirements, to promote groundwater recharge and to otherwise meet the purposes of this Ordinance.

Best Management Practice Operations and Maintenance Plan – Documentation, included as part of a Drainage Plan, detailing the proposed BMPs, how they will be operated and maintained and who will be responsible.

Bioretention – Densely vegetated, depressed features that store stormwater and filter it through vegetation, mulch, planting soil, etc. Ultimately stormwater is evapotranspirated, infiltrated, or discharged. Optimal bioretention areas mimic natural forest ecosystems in terms of species diversity, density, distribution, use of native plants, etc.

Buffer – (1) Streamside Buffer - A zone of variable width located along a stream that is vegetated and is designed to filter pollutants from runoff.
(2) Special Geologic Feature Buffer – A required isolation distance from a special geologic feature to a proposed BMP needed to reduce the risk of sinkhole formation due to stormwater management activities.

Capture/Reuse – Stormwater management techniques such as cisterns and rain barrels which direct runoff into storage devices, surface or sub-surface, for later re-use, such as for irrigation of gardens and other planted areas. Because this stormwater is utilized and no pollutant discharge results, water quality performance is superior to other non-infiltration BMPs.

Carbonate Bedrock – Rock consisting chiefly of carbonate minerals, such as limestone and dolomite; specifically a sedimentary rock composed of more than 50% by weight of carbonate minerals that underlies soil or other unconsolidated, superficial material.

Cistern – An underground reservoir or tank for storing rainwater.

City – City of Bethlehem.

Closed Depression – A distinctive bowl-shaped depression in the land surface. It is characterized by internal drainage, varying magnitude, and an unbroken ground surface.

Conservation District – The Lehigh or Northampton County Conservation District, as applicable.

Constructed Wetlands – Constructed wetlands are similar to wet ponds (see below) and consist of a basin which provides for necessary stormwater storage as well as a permanent pool or water level, planted with wetland vegetation. To be successful, constructed wetlands must have adequate natural hydrology (both runoff inputs as well as soils and water table which allow for maintenance of a permanent pool of water). In these cases, the permanent pool must be designed carefully, usually with shallow edge benches, so that water levels are appropriate to support carefully selected wetland vegetation.

Culvert – A pipe, conduit or similar structure including appurtenant works which carries surface water.

Dam – An artificial barrier, together with its appurtenant works, constructed for the purpose of impounding or storing water or another fluid or semifluid or a refuse bank, fill or structure for highway, railroad or other purposes which does or may impound water or another fluid or semifluid.

DEP – The Pennsylvania Department of Environmental Protection (formerly the Pennsylvania Department of Environmental Resources).

Design Storm – The depth and time distribution of precipitation from a storm event measured in probability of occurrence (e.g., 50-yr. storm) and duration (e.g. 24-hour), and used in computing stormwater management control systems.

Detention Basin – A basin designed to retard stormwater runoff by temporarily storing the runoff and releasing it at a predetermined rate.

Developer – A person, partnership, association, corporation or other entity, or any responsible person therein or agent thereof, that undertakes any Regulated Activity of this Ordinance.

Development Site – The specific tract of land for which a Regulated Activity is proposed.

Diffused Drainage – See Sheet Flow.

Drainage Easement – A right granted by a land owner to a grantee, allowing the use of private land for stormwater management purposes.

Drainage Plan – The documentation of the proposed stormwater quantity and quality management controls to be used for a given development site, including a BMP Operations and Maintenance Plan, the contents of which are established in Section 925.21.

Earth Disturbance Activity – A construction or other human activity which disturbs the surface of the land, including, but not limited to, clearing and grubbing, grading, excavations, embankments, road maintenance, building construction and the moving, depositing, stockpiling or storing of soil, rock or earth materials.

Erosion – The removal of soil particles by the action of water, wind, ice, or other geological agents.

Existing Uses – Those uses actually attained in the water body on or after November 28, 1975, whether or not they are included in the water quality standards. (25 Pa. Code Chapter 93.1)

Fill – Man-made deposits of natural soils or rock products and waste materials.

Filter Strips – see Vegetated Buffers.

Freeboard – The incremental depth in a stormwater management structure, provided as a safety factor of design, above that required to convey the design runoff event.

Groundwater Recharge – Replenishment of existing natural underground water supplies.

Hardship Waiver Request – A written request for a waiver alleging that the provisions of this Ordinance inflict unnecessary hardship upon the applicant. Waivers from the water quality provisions of this Ordinance shall not be granted.

Hot Spot Land Uses – A Land Use or activity that generates higher concentrations of hydrocarbons, trace metals or other toxic substances than typically found in stormwater runoff. These land uses are listed in Section 925.15P.

Hydrologic Soil Group (HSG) – Soils are classified into four HSGs (A, B, C and D) to indicate the minimum infiltration rates, which are obtained for bare soil after prolonged wetting. The Natural Resources Conservation Service (NRCS) of the US Department of Agriculture defines the four groups and provides a list of most of the soils in the United States and their group classification. The soils in the area of the development site may be identified from a soil survey report that can be obtained from local NRCS offices or conservation district offices. Soils become less permeable as the HSG varies from A to D.

Impervious Surface (Impervious Cover) – A surface which prevents the percolation of water into the ground.

Infiltration Practice – A practice designed to direct runoff into the ground, e.g. French drain, seepage pit, seepage trench or bioretention area.

Infiltration Structure – A structure designed to direct runoff into the ground, e.g. French drain, seepage pit, trench or perforated pipe or similar.

Karst – A type of topography or landscape characterized by depressions, sinkholes, limestone towers and steep-sided hills, underground drainage and caves. Karst is usually formed on carbonate rocks, such as limestones or dolomites and sometimes gypsum.

Land Development – (i) the improvement of one lot or two or more contiguous lots, tracts or parcels of land for any purpose involving (a) a group of two or more buildings, or (b) the division or allocation of land or space between or among two or more existing or prospective occupants by means of, or for the purpose of streets, common areas, leaseholds, condominiums, building groups or other features; (ii) a subdivision of land; (iii) development in accordance with Section 503(1.1) of the Pennsylvania Municipalities Planning Code.

Loading Rate – The ratio of the land area draining to the system, as modified by the weighting factors in Section 925.18B, compared to the base area of the infiltration system.

Low Impact Development – A development approach that promotes practices that will minimize post-development runoff rates and volumes thereby minimizing needs for artificial conveyance and storage facilities. Site design practices include preserving natural drainage features, minimizing impervious surface area, reducing the hydraulic connectivity of impervious surfaces, and protecting natural depression storage.

“Local” Runoff Conveyance Facilities – Any natural channel or manmade conveyance system which has the purpose of transporting runoff from the site to the mainstream.

LVPC – Lehigh Valley Planning Commission of Lehigh and Northampton Counties.

Mainstem (main channel) – Any stream segment or other conveyance used as a reach in the Lehigh, Monocacy, Nancy Run or Saucon Creek hydrologic model.

Manning Equation (Manning formula) – A method for calculation of velocity of flow (e.g. feet per second) and flow rate (e.g. cubic feet per second) in open channels based upon channel shape, roughness, depth of flow and slope. “Open channels” may include closed conduits so long as the flow is not under pressure.

Maryland Stormwater Design Manual – A stormwater design manual written by the Maryland Department of the Environment and the Center for Watershed Protection. As of January 2004, the Manual can be obtained through the following web site: www.mde.state.md.us.

Minimum Disturbance/Minimum Maintenance Practices (MD/MM) – A site design practice in which careful limits are placed on site clearance prior to development allowing for maximum retention of existing vegetation (woodlands and other), minimum disturbance and compaction of existing soil mantle and minimum site application of chemicals post-development. Typically, MD/MM includes disturbance setback criteria from buildings as well as related site improvements such as walkways, driveways, roadways, and any other improvements. These criteria may vary by community context as well as by type of development being proposed. Additionally, MD/MM also shall include provisions (e.g., deed restrictions, conservation easements) to protect these areas from future disturbance and from application of fertilizers, pesticides, and herbicides.
Municipality – City of Bethlehem, Lehigh or Northampton County (as applicable), Pennsylvania.

No Harm Option – The option of using a less restrictive runoff quantity control if it can be shown that adequate and safe runoff conveyance exists and that the less restrictive control would not adversely affect health, safety and property.

NPDES – National Pollutant Discharge Elimination System.

NRCS – Natural Resource Conservation Service - U.S. Department of Agriculture. (Formerly the Soil Conservation Service.)

Oil/Water Separator – A structural mechanism designed to remove free oil and grease (and possibly solids) from stormwater runoff.

Open Channel – Any storm water conveyance facility through which water normally flows by gravity. An open channel may be exposed, such as a swale, street gutter, or stream; or unexposed such as a culvert.

Outfall – “Point source” as described in 40 CFR § 122.2 at the point where the City’s storm sewer system discharges to surface waters of the Commonwealth.

Peak Discharge – The maximum rate of flow of stormwater runoff at a given location and time resulting from a specified storm event.

Penn State Runoff Model (PSRM) – The computer-based hydrologic modeling technique used in previous Act 167 Plans. PSRM was also updated to include water quality modeling capabilities and renamed PSRM-QUAL. The PSRM and PSRM-QUAL calculation methodologies were used as the basis for writing the WATERSHED model.

Person – An individual, partnership, public or private association or corporation, or a governmental unit, public utility or other for or not for profit statutory entity or other legal entity whatsoever which is recognized by law as the subject of rights and duties.

Point Source – any discernible, confined and discrete conveyance, including, but not limited to, any pipe, ditch, channel, tunnel or conduit from which stormwater is or may be discharged, as defined in State regulations at 25 Pa. Code § 92.1.

Preliminary Site Investigation – The determination of the depth to bedrock, the depth to the seasonal high water table and the soil permeability for a possible infiltration location on a site through the use of published data and on-site surveys. In carbonate bedrock areas, the location of special geologic features must also be determined along with the associated buffer distance to the possible infiltration area. See Appendix G.

Public Water Supplier – A person who owns or operates a public water system.

Public Water System – A system which provides water to the public for human consumption which has at lest 15 service connections or regularly serves an average of at least 25 individuals daily at least 60 days out of the year. (See 25 Pa. Code Chapter 109)

Qualified Geotechnical Professional – A licensed professional geologist or a licensed professional engineer who has a background or expertise in geology or hydrogeology.

Rational Method – A method of peak runoff calculation using a standardized runoff coefficient (rational ‘c’), acreage of tract and rainfall intensity determined by return period and by the time necessary for the entire tract to contribute runoff. The rational method formula is stated as follows: Q = ciA, where “Q” is the calculated peak flow rate in cubic feet per second, “c” is the dimensionless runoff coefficient (see Appendix C), “i” is the rainfall intensity in inches per hour, and “A” is the area of the tract in acres.

Reach – Any of the natural or man-made runoff conveyance channels used for watershed runoff modeling purposes to connect the subareas and transport flows downstream.

Recharge Volume (Rev) – The portion of the water quality volume (WQv) used to maintain groundwater recharge rates at development sites. (see Section 925.15J)

Regulated Activities – Actions or proposed actions which impact upon proper management of stormwater runoff and which are governed by this Ordinance as specified in Section 925.05.

Regulated Earth Disturbance Activities – Earth disturbance activity of one acre or more with a point source discharge to surface waters or to the municipality’s storm sewer system or earth disturbance activity of five acres or more regardless of the planned runoff. This includes earth disturbance on any portion of, part or during any stage of a larger common plan of development.

Release Rate – The percentage of the pre-development peak rate of runoff for a development site to which the post-development peak rate of runoff must be controlled to avoid peak flow increases throughout the watershed.

Return Period – The average interval in years over which an event of a given magnitude can be expected to recur. For example, the twenty-five (25) year return period rainfall or runoff event would be expected to recur on the average once every twenty-five years.

Road Maintenance – Earth disturbance activities within the existing road cross-section such as grading and repairing existing unpaved road surfaces, cutting road banks, cleaning or clearing drainage ditches and other similar activities.

Runoff – That part of precipitation which flows over the land.

Sediment Traps/Catch Basin Sumps – A chamber which provides storage below the outlet in a storm inlet to collect sediment, debris and associated pollutants, typically requiring periodic clean out.

Seepage Pit/Seepage Trench – An area of excavated earth filled with loose stone or similar material and into which surface water is directed for infiltration into the ground.

Separate Storm Sewer System – A conveyance or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels or storm drains) primarily used for collecting and conveying stormwater runoff.

Sheet Flow – Stormwater runoff flowing in a thin layer over the ground surface.

Soil-Cover-Complex Method – A method of runoff computation developed by NRCS which is based upon relating soil type and land use/cover to a runoff parameter called a Curve Number.

Special Geologic Features – Carbonate bedrock features, including but not limited to closed depressions, existing sinkholes, fracture traces, lineaments, joints, faults, caves and pinnacles, which may exist and must be identified on a site when stormwater management BMPs are being considered.

Spill Prevention and Response Program – A program that identifies procedures for preventing and, as needed, cleaning up potential spills and makes such procedures known and the necessary equipment available to appropriate personnel.

State Water Quality Requirements – As defined under state regulations -- protection of designated and existing uses (See 25 Pa. Code Chapters 93 and 96)--including:

A. Each stream segment in Pennsylvania has a “designated use,” such as “cold water fishes” or “potable water supply,” which are listed in Chapter 93. These uses must be protected and maintained, under state regulations.
B. “Existing uses” are those attained as of November 1975, regardless whether they have been designated in Chapter 93. Regulated Earth Disturbance activities must be designed to protect and maintain existing uses and maintain the level of water quality necessary to protect those uses in all streams, and to protect and maintain water quality in special protection streams.
C. Water quality involves the chemical, biological and physical characteristics of surface water bodies. After Regulated Earth Disturbance activities are complete, these characteristics can be impacted by addition of pollutants such as sediment, and changes in habitat through increased flow volumes and/or rates as a result of changes in land surface area from those activities. Therefore, permanent discharges to surface waters must be managed to protect the stream bank, streambed and structural integrity of the waterway, to prevent these impacts.

Storage Indication Method – A method of routing or moving an inflow hydrograph through a reservoir or detention structure. The method solves the mass conservation equation to determine an outflow hydrograph as it leaves the storage facility.

Storm Drainage Problem Areas – Areas which lack adequate stormwater collection and/or conveyance facilities and which present a hazard to persons or property.

Storm Sewer – A system of pipes or other conduits which carries intercepted surface runoff, street water and other wash waters, or drainage, but excludes domestic sewage and industrial wastes.

Stormwater – The surface runoff generated by precipitation reaching the ground surface.

Stormwater Filters – Any number of structural mechanisms such as multi-chamber catch basins, sand/peat filters, sand filters, and so forth, which are installed to intercept stormwater, flow and remove pollutants prior to discharge. Typically, these systems require periodic maintenance and clean out.

Stormwater Management Plan – The plan for managing stormwater runoff adopted by Lehigh and Northampton Counties for the Lehigh, Monocacy, Nancy Run or Saucon Creek Watersheds as required by the Act of October 4, 1978, P.L. 864, (Act 167), as amended, and known as the “Stormwater Management Act”.

Stream – A watercourse.

Subarea – The smallest unit of watershed breakdown for hydrologic modeling purposes for which the runoff control criteria have been established in the Stormwater Management Plan.

Subdivision – The division or redivision of a lot, tract or parcel of land by any means into two or more lots, tracts, parcels or other divisions of land including changes in existing lot lines for the purpose, whether immediate or future, of lease, partition by the court for distribution to heirs or devisees, transfer of ownership or building or lot ownership: Provided, however, that the subdivision by lease of land for agricultural purposes into parcels of more than ten acres, not involving any new street or easement of access or any residential dwelling, shall be exempted.

Surface Waters of the Commonwealth – Any and all rivers, streams, creeks, rivulets, impoundments, ditches, watercourses, storm sewers, lakes, dammed water, wetlands, ponds, springs and all other bodies or channels of conveyance of surface water, or parts thereof, whether natural or artificial, within or on the boundaries of this Commonwealth.

Swale – A low-lying stretch of land which gathers or carries surface water runoff. See also Vegetated Swale.

Technical Best Management Practice Manual & Infiltration Feasibility Report, November 2002 – The report written by Cahill Associates that addresses the feasibility of infiltration in carbonate bedrock areas in the Little Lehigh Creek Watershed. The report is available at the LVPC offices.

Trash/Debris Collectors – Racks, screens or other similar devices installed in a storm drainage system to capture coarse pollutants (trash, leaves, etc.).

Vegetated Buffers – Gently sloping areas that convey stormwater as sheet flow over a broad, densely vegetated earthen area, possibly coupled with the use of level spreading devices. Vegetated buffers should be situated on minimally disturbed soils, have low-flow velocities and extended residence times.

Vegetated Roofs – Vegetated systems installed on roofs that generally consist of a waterproof layer, a root-barrier, drainage layer (optional), growth media, and suitable vegetation. Vegetated roofs store and eventually evapotranspirate the collected rooftop rainfall; overflows may be provided for larger storms.

Vegetated Swales – (1) Vegetated earthen channels designed to convey stormwater. These swales are not considered to be water quality BMPs. (2) Broad, shallow, densely vegetated, earthen channels designed to treat stormwater while slowly infiltrating, evapotranspirating, and conveying it. Swales should be gently sloping with low flow velocities to prevent erosion. Check dams may be added to enhance performance.

Water Quality Inserts – Any number of commercially available devices that are inserted into storm inlets to capture sediment, oil, grease, metals, trash, debris, etc.

Water Quality Volume (WQv) – The volume needed to capture and treat 90% of the average annual rainfall volume. (see Section 925.15B)

Watercourse – Any channel of conveyance of surface water having defined bed and banks, whether natural or artificial, with perennial or intermittent flow.

Watershed – The entire region or area drained by a river or other body of water, whether natural or artificial.

WATERSHED – The computer-based hydrologic modeling technique adapted to the Lehigh, Monocacy, Nancy Run or Saucon Creek Watersheds for the Act 167 Plan. This model was written by Tarsi Software Laboratories and uses the same algorithms found in the Penn State Runoff Quality Model (PSRM-QUAL). The model has been “calibrated” to reflect actual flow values by adjusting key model input parameters.

Wet Detention Ponds – A basin that provides for necessary stormwater storage as well as a permanent pool of water. To be successful, wet ponds must have adequate natural hydrology (both runoff inputs as well as soils and water table which allow for maintenance of a permanent pool of water) and must be able to support a healthy aquatic community so as to avoid creation of mosquito and other health and nuisance problems.

SECTION 2
STORMWATER MANAGEMENT REQUIREMENTS

925.12 GENERAL REQUIREMENTS

A. All storm drainage systems shall be constructed as necessary to convey the flow of surface waters without damage to persons or property. These drainage systems shall be constructed as approved by the City Engineer to drain the storm water runoff from the applicant’s land, as well as the collected runoff from development(s) at higher elevations in the same watershed. Should the land at a higher elevation be undeveloped, the design of the storm drainage system local to the applicant shall be designed as if the land above were fully developed in accordance with current zoning regulations and assuming that required runoff controls are in effect in all tributary areas.

B. Storm drainage systems shall be provided to permit unimpeded flow in natural watercourses except as modified by stormwater detention facilities, recharge facilities, water quality facilities, pipe systems or open channels consistent with this Ordinance. Storm drainage systems shall provide positive drainage away from buildings and on-site sewage disposal systems and prevent overloading of downstream drainage systems and watercourses as a result of increased rate of runoff caused by the proposed development.

C. The existing locations of concentrated drainage discharge onto adjacent property shall not be altered without written approval of the affected property owner(s) and the City Engineer.

D. Areas of existing diffused drainage discharge onto adjacent property shall be managed such that, at minimum, the peak diffused flow does not increase in the general direction of discharge, except as otherwise provided in this Ordinance. If diffused flow is proposed to be concentrated and discharged onto adjacent property, the developer must document that there are adequate downstream conveyance facilities to safely transport the concentrated discharge to the point of pre-development flow concentration, to the stream reach or otherwise prove that no harm will result from the concentrated discharge. Areas of existing diffused drainage discharge shall be subject to any applicable release rate criteria in the general direction of existing discharge whether they are proposed to be concentrated or maintained as diffused drainage areas.

E. Where a site is traversed by watercourses other than those for which a 100-year floodplain is defined by the municipality, there shall be provided drainage easements conforming substantially with the line of such watercourses. The width of any easement shall be adequate to provide for unimpeded flow of storm runoff based on calculations made in conformance with Section 925.18 for the 100-year return period runoff and to provide a freeboard allowance of one-half (0.5) foot above the design water surface level. The terms of the easement shall prohibit excavation, the placing of fill or structures, and any alterations which may adversely affect the flow of stormwater within any portion of the easement. Also, periodic maintenance of the easement to ensure proper runoff conveyance shall be required. Watercourses for which the 100-year floodplain is formally defined are subject to the applicable municipal floodplain regulations.

F. When it can be shown that, due to topographic conditions, natural drainage swales on the site cannot adequately provide for drainage, open channels may be constructed conforming substantially to the line and grade of such natural drainage swales. Capacities of open channels shall be calculated using the Manning equation.

G. Post-construction storm drainage facilities and appurtenances shall be designed and provided in accordance with the established practices in 25 Pa. Code Chapter 102 and the specifications of this ordinance as to prevent erosion in watercourse channels and at all points of discharge.

H. No Earth Disturbance activities associated with any Regulated Activities shall commence until approval by the City of a plan which demonstrates compliance with the requirements of this Ordinance.

I. Techniques described in Appendix F (Low Impact Development) of this Ordinance are encouraged because they reduce the costs of complying with the requirements of this Ordinance and the State Water Quality Requirements.

J. Infiltration for stormwater management is encouraged where soils and geology permit, consistent with the provisions of this Ordinance and, where appropriate, the Recommendation Chart for Infiltration Stormwater Management BMPs in Carbonate Bedrock in Appendix D. Infiltration is encouraged for capturing and treating the Water Quality Volume (as calculated in Section 925.15), any part of the Water Quality Volume or for otherwise meeting the purposes of this Ordinance.

925.13. PERMIT REQUIREMENTS BY OTHER GOVERNMENT ENTITIES

A. The following permit requirements apply to certain Regulated and Earth Disturbance activities and must be met prior to commencement of Regulated and Earth Disturbance activities, as applicable:

1. All Regulated and Earth Disturbance activities subject to permit requirements by DEP under regulations at 25 Pa. Code Chapter 102.

2. Work within natural drainageways subject to permit by DEP under 25 Pa. Code Chapter 102.

3. Any stormwater management facility that would be located in or adjacent to surface waters of the Commonwealth, including wetlands, subject to permit by DEP under 25 Pa. Code Chapter 105.

4. Any stormwater management facility that would be located on a State highway right-of-way or require access from a State highway shall be subject to approval by the Pennsylvania Department of Transportation (PENNDOT).

5. Culverts, bridges, storm sewers or any other facilities which must pass or convey flows from the tributary area and any facility which may constitute a dam subject to permit by DEP under 25 Pa. Code Chapter 105.

925.14. EROSION AND SEDIMENT CONTROL DURING REGULATED EARTH DISTURBANCE ACTIVITIES

A. No Regulated Earth Disturbance activities within the City shall commence until approval by the City of an Erosion and Sediment Control Plan for construction activities.

It is the intent of this section of this ordinance to require that proper erosion control be maintained on all land regardless of the area of land intentionally disturbed (if any) and regardless of the status of any construction on the land. Should the City Engineer determine that erosion control on any area of land is deficient and impacting or threatening to impact on offsite land, either directly or indirectly (such as through the creation of sinkholes that may travel offsite), the City Engineer may require that corrective action be taken in an expeditious manner. This corrective action shall be completed as soon as possible, but no later than 10 days from the date of notification of the deficiency.

Should the City Engineer determine that erosion control is deficient during construction, the City Engineer may pull all construction permits acquired from the City and- except for corrective erosion control work- stop the job until, in the opinion of the City Engineer, adequate correction of erosion control deficiencies has been made.

B. An Erosion and Sediment Control Plan is required by DEP regulations for any earth disturbance activity of 5,000 square feet or more under Pa. Code § 102.4(b).

C. A DEP NPDES Stormwater Discharges Associated with Construction Activities permit is required for Regulated Earth Disturbance activities under Pa. Code Chapter 92.

D. Evidence of any necessary permit(s) for Regulated Earth Disturbance Activities from the appropriate DEP regional office or County Conservation District must be provided to the City before the commencement of an earth disturbance activity.

E. A copy of the Erosion and Sediment Control Plan and any permit, as required by DEP regulations, shall be available at the project site at all times.

925.15 POST CONSTRUCTION WATER QUALITY CRITERIA

A. No Regulated Earth Disturbance activities within the City shall commence until approval by the City of a Drainage Plan which demonstrates compliance with this Ordinance. This Ordinance provides standards to meet NPDES Permit requirements associated with construction activities and MS4 permit requirements.

B. The Water Quality Volume (WQv) shall be captured and treated. The WQv shall be calculated two ways. First, WQv shall be calculated using the following formula:

Where WQv = water quality volume in acre-feet
c = Rational Method post-development runoff coefficient for the 2-year storm
P = 1.25 inches
A = site area in acres

Second, the WQv shall be calculated as the difference in runoff volume from pre-development to post-development for the 2-year return period storm. The effect of closed depressions on the site shall be considered in this calculation. The larger of these two calculated volumes shall be used as the WQv to be captured and treated, except that in no case shall the WQv be permitted to exceed 1.25-inches of runoff over the site area. This standard does not limit the volume of infiltration an applicant may propose for purposes of water quantity/peak rate control.

C. The WQv shall be calculated for each post-development drainage direction on a site for sizing BMPs. Site areas having no impervious cover and no proposed disturbance during development may be excluded from the WQv calculations and do not require treatment.

D. If an applicant is proposing to use a dry extended detention basin, wet pond, constructed wetland or other BMP that ponds water on the land surface and may receive direct sunlight, the discharge from that BMP must be treated by infiltration, a vegetated buffer, filter strip, bioretention, vegetated swale or other BMP that provides a thermal benefit to protect the High Quality waters of the Monocacy and Saucon Creeks from thermal impacts.

E. The WQv for a site as a result of the Regulated Activities must either be treated with infiltration or two acceptable BMPs as listed in Section 925.15O, except for minor areas on the periphery of the site that cannot reasonably be drained to an infiltration facility or other BMP.

F. Infiltration BMPs shall not be constructed on fill unless the applicant demonstrates that the fill is stable and otherwise meets the infiltration BMP standards of this Ordinance.

G. The applicant shall document the bedrock type(s) present on the site from published sources. Any apparent boundaries between carbonate and non-carbonate bedrock shall be verified through more detailed site evaluations by a qualified geotechnical professional.

H. For each proposed development in the watershed, the applicant shall conduct a preliminary site investigation on the portion of the site that is judged to be the best candidate hydrogeologically for possible infiltration, including gathering data from published sources, a field inspection of the site, a minimum of one test pit and a minimum of two percolation tests, as outlined in Appendix G. This investigation will determine depth to bedrock, depth to the seasonal high water table, soil permeability and location of special geologic features, if applicable. This investigation may be done by a certified Sewage Enforcement Officer (SEO) except that the location(s) of special geologic features shall be verified by a qualified geotechnical professional.

I. Sites where applicants intend to use infiltration BMP’s must meet the following criteria:

• Depth to bedrock below the invert of the BMP greater than or equal to 2 feet
• Depth to seasonal high water table below the invert of the BMP greater than or equal to 3 feet; except for infiltration of residential roof runoff where the seasonal high water table must be below the invert of the BMP. (If the depth to bedrock is between 2 and 3 feet and the evidence of the seasonal high water table is not found in the soil, no further testing to locate the depth to seasonal high water table is required)
• Soil permeability (as measured by the adapted 25 PA Code 73.15. percolation test in Appendix G) greater than or equal to 0.5 inches/hour and less than or equal to 12 inches per hour
• Setback distances or buffers as follows:
– 100 feet from water supply wells
– 15 feet downgradient or 100 feet upgradient from building foundations; except for residential development where the required set back is 15 feet downgradient or 40 feet upgradient from building foundations.
– 50 feet from septic system drainfields; except for residential development where the required setback is 25 feet from septic drainfields.
– 50 feet from a geologic contact with carbonate bedrock unless a preliminary site investigation is done in the carbonate bedrock to show the absence of special geologic features within 50 feet of the proposed infiltration area.
– 100 feet from the property line unless documentation is provided to show that all setbacks from wells, foundations and drainfields on neighboring properties will be met; except for one and two family residential dwellings where the required setback is 40 feet unless documentation is provided to show that all setbacks from existing or potential future wells, foundations and drainfields on neighboring properties will be met.

If it is not feasible to infiltrate the full WQv, the applicant shall infiltrate that portion of the WQv that is feasible based on the site characteristics.

J. For entirely non-carbonate sites, the Recharge Volume (REv) shall be infiltrated
unless the applicant demonstrates that it is infeasible to infiltrate the REv for reasons
of seasonal high water table, permeability rate, soil depth or setback distances; or
except as provided in Section 925.15U.

1. The REv shall be calculated as follows:

REv = (0.25) * (I)/12

Where REv = Recharge Volume in acre-feet
I = impervious area in acres

2. The Preliminary Site Investigation described in Section 925.15H. is required and
shall continue on different areas of the site until a potentially suitable infiltration
location is found or the entire site is determined to be infeasible for infiltration.
For infiltration areas that appear to be feasible based on the preliminary site
investigation, the Additional Site Investigation and Testing as outlined in
Appendix G shall be completed.

3. If an Applicant proposes infiltration, the municipality may determine infiltration
to be infeasible if there are known existing conditions or problems that may be
worsened by the use of infiltration.

4. The site must meet the conditions listed in Section 925.15I.

5. If it is not feasible to infiltrate the full REv, the applicant shall infiltrate that
portion of the REv that is feasible based on the site characteristics. If none of
the REv can be infiltrated, REv shall be considered as part of the WQv and shall
be captured and treated as described in Section 925.15O.

6. If REv is infiltrated, it may be subtracted from the WQv required to be captured
and treated.

K. In entirely carbonate areas, where the applicant intends to use infiltration BMPs, the
Preliminary Site Investigation described in Section 925.15H. shall be conducted. For
infiltration areas that appear feasible based on the Preliminary Site Investigation, the
applicant shall conduct the Additional Site Investigation and Testing as outlined in
Appendix G. The soil depth, percolation rate and proposed loading rate, each
weighted as described in Section 925.18, along with the buffer from special geologic
features shall be compared to the Recommendation Chart for Infiltration Stormwater
Management BMPs in Carbonate Bedrock in Appendix D to determine if the site is
recommended for infiltration. In addition to the recommendation from Appendix D,
the conditions listed in Section 925.15.I. are required for infiltration in carbonate areas.

Applicants are encouraged to infiltrate the REv, as calculated in Section 925.15J, but
are not required to use infiltration BMPs on a carbonate site even if the site falls in
the “Recommended” range on the chart in Appendix D. Any amount of volume
infiltrated can be subtracted from the WQv to be treated by non-infiltration BMPs. If
infiltration is not proposed, the full WQv shall be treated by two acceptable BMPs, as
specified in Section 925.15O.

L. If a site has both carbonate and non-carbonate areas, the applicant shall investigate
the ability of the non-carbonate portion of the site to fully meet this Ordinance to
meet the requirements for REv for the whole site through infiltration. If that proves
infeasible, infiltration in the carbonate area as described in Section 304.K. or 2 other
non-infiltration BMPs as described in Section 304.O. must be used. No infiltration
structure in the non-carbonate area shall be located within 50 feet of a boundary with
carbonate bedrock, except when a Preliminary Site Investigation has been done
showing the absence of special geologic features within 50 feet of the proposed
infiltration area.

M. If infiltration BMPs are proposed in carbonate areas, the post-development 2-year runoff volume leaving the site shall be 80% or more of the pre-development runoff volume for the carbonate portion of the site to prevent infiltration of volumes far in excess of the pre-development infiltration volume.

N. Site areas proposed for infiltration shall be protected from disturbance and compaction except as necessary for construction of infiltration BMPs.

O. If infiltration is not proposed, the WQv shall be treated by two acceptable BMPs in series for each discharge location. Sheet flow draining across a pervious area can be considered as one BMP. Sheet flow across impervious areas and concentrated flow shall flow through two BMPs. If sheet flow from an impervious area is to be drained across a pervious area as one BMP, the length of the pervious area must be equal to or greater than the length of impervious area. In no case, may the same BMP be employed consecutively to meet this requirement. Acceptable BMPs are listed below along with the recommended reference for design.

Best Management Practice Design Reference
BioretentionA 4,5,11,16
Capture/Reuse1B 4,14
Constructed Wetlands 4,5,8,10,16
Dry Extended Detention Ponds 4,5,8,12,18
Minimum Disturbance/
Minimum Maintenance Practices 1,9
Significant Reduction of Existing Impervious Cover N/A
Stormwater FiltersA (Sand, Peat, Compost, etc.) 4,5,10,16
Vegetated Buffers/Filter Strips 2,3,5,11,16,17
Vegetated Roofs 4,13
Vegetated SwalesA 2,3,5,11,16,17
Water Quality Inserts for InletsD 4,7,15,16,19
Wet Detention Ponds
4,5,6,8

A This BMP could be designed with or without an infiltration component. If infiltration is proposed, the site and BMP will be subject to the testing and other infiltration requirements in this Ordinance.
B If this BMP is used to treat the entire WQv then it is the only BMP required because of this BMPs superior water quality performance.
C See table below.
D Water Quality Inlets include such BMPs as Oil/Water Separators, Sediment Traps/Catch Basin Sumps, and Trash/Debris Collectors in Catch Basins.

Number Design Reference Title
1 “Conservation Design For Stormwater Management – A Design Approach to
Reduce Stormwater Impacts From Land Development and Achieve Multiple
Objectives Related to Land Use”, Delaware Department of Natural Resources
and Environmental Control, The Environmental Management Center of the
Brandywine Conservancy, September 1997
2 “A Current Assessment of Urban Best Management Practices: Techniques for Reducing Nonpoint Source Pollution in the Coastal Zone”, Schueler, T. R., Kumble, P. and Heraty, M., Metropolitan Washington Council of Governments, 1992.
3 “Design of Roadside Channels with Flexible Linings”, Federal Highway
Administration, Chen, Y. H. and Cotton, G. K., Hydraulic Engineering
Circular 15, FHWA-IP-87-7, McLean Virginia, 1988.
4 “Draft Stormwater Best Management Practices Manual”, Pennsylvania
Department of Environmental Protection, January 2005.
5 “Evaluation and Management of Highway Runoff Water Quality”, Federal
Highway Administration, FHWA-PD-96-032, Washington, D.C., 1996.
6 “Evaporation Maps of the United States”, U.S. Weather Bureau (now
NOAA/National Weather Service) Technical Paper 37, Published by
Department of Commerce, Washington D.C., 1959.
Number Design Reference Title
7 “Georgia Stormwater Manual”, AMEC Earth and Environmental, Center for
Watershed Protection, Debo and Associates, Jordan Jones and Goulding,
Atlanta Regional Commission, Atlanta, Georgia, 2001.
8 “Hydraulic Design of Highway Culverts”, Federal Highway Administration,
FHWA HDS 5, Washington, D.C., 1985 (revised May 2005).
9 “Low Impact Development Design Strategies An Integrated Design Approach, Prince Georges County, Maryland Department of Environmental Resources, June 1999.
10 “Maryland Stormwater Design Manual”, Maryland Department of the
Environment, Baltimore, Maryland , 2000.
11 “Pennsylvania Handbook of Best Management Practices for Developing
Areas”, Pennsylvania Department of Environmental Protection, 1998.
12 “Recommended Procedures for Act 167 Drainage Plan Design”, LVPC,
Revised 1997.
13 “Roof Gardens History, Design, and Construction”, Osmundson, Theodore.
New York: W.W. Norton & Company, 1999.
14 “The Texas Manual on Rainwater Harvesting”, Texas Water Development
Board, Austin, Texas, Third Edition, 2005.
15 “VDOT Manual of Practice for Stormwater Management”, Virginia
Transportation Research Council, Charlottesville, Virginia, 2004
16 “Virginia Stormwater Management Handbook”, Virginia Department of
Conservation and Recreation, Richmond, Virginia, 1999.
17 “Water Resources Engineering”, Mays, L. W., John Wiley & Sons, Inc., 2005.
18 “Urban Hydrology for Small Watersheds”, Technical Report 55, US
Department of Agriculture, Natural Resources Conservation Service, 1986.
19 US EPA, Region 1 New England web site (as of August 2005)
http://www.epa.gov/NE/assistance/ceitts/stormwater/techs/html.

P. Stormwater runoff from Hot Spot land uses, as defined in Section 925.11, shall be pre-treated. In no case, may the same BMP be employed consecutively to meet this requirement and the requirement in Section 925.15O. Acceptable methods of pre-treatment are listed below.

Hot Spot Land Use Pre-treatment Method(s)
Vehicle Maintenance and Repair Facilities including Auto Parts Stores -Water Quality Inlets
-Use of Drip Pans and/or Dry Sweep Material Under Vehicles/Equipment
-Use of Absorbent Devices to Reduce Liquid Releases
-Spill Prevention and Response Program
Vehicle Fueling Stations -Water Quality Inserts for Inlets
-Spill Prevention and Response Program
Hot Spot Land Use Pre-treatment Method(s)
Storage Areas for Public Works -Water Quality Inserts for Inlets
-Use of Drip Pans and/or Dry Sweep Material Under Vehicles/Equipment
-Use of Absorbent Devices to Reduce Liquid Releases
-Spill Prevention and Response Program
-Diversion of Stormwater away from Potential Contamination Areas
Outdoor Storage of Liquids -Spill Prevention and Response Program
Commercial Nursery Operations -Vegetated Swales/Filter Strips
-Constructed Wetlands
-Stormwater Collection and Reuse
Salvage Yards and Recycling Facilities* -BMPs that are a part of a Stormwater Pollution Prevention Plan under an NPDES Permit
Fleet Storage Yards and Vehicle Cleaning Facilities* -BMPs that are a part of a Stormwater Pollution Prevention Plan under an NPDES Permit
Facilities that Store or Generate Regulated Substances* -BMPs that are a part of a Stormwater Pollution Prevention Plan under an NPDES Permit
Marinas* -BMPs that are a part of a Stormwater Pollution Prevention Plan under an NPDES Permit
Certain Industrial Uses (listed under NPDES)* -BMPs that are a part of a Stormwater Pollution Prevention Plan under an NPDES Permit
*Regulated under the NPDES Stormwater Program

Design references for the pre-treatment methods, as necessary, are listed below. An applicant may use an alternate design reference if use of the alternate reference can be justified. Alternatives may include providing documentation demonstrating that water quality has been protected or otherwise demonstrating that due to the site characteristics the land use is not a Hot Spot as defined in Section 925.11. Where the documented design methodology conflicts with the provisions of this Ordinance, this Ordinance shall govern.

Pre-treatment Method Design ReferenceA
Constructed Wetlands 5,6,10,12,18
Diversion of Stormwater away from Potential Contamination Areas 5,13
Stormwater Collection and Reuse (especially for irrigation) 5,16
Stormwater Filters (Sand, Peat, Compost, etc.) 5,6,12,18

Vegetated Swales 2,4,6,13,18,19
Water Quality Inlets 5,9,17,18,21
AThese numbers refer to the Design Reference Title Chart in Section 925.15O

Q. The use of infiltration BMPs is prohibited on Hot Spot land uses.

R. Stormwater infiltration facilities shall not be placed in or on a special geologic
feature(s). Additionally, stormwater runoff shall not be discharged into existing on-site sinkholes.

S. Applicants shall request, in writing, Public Water Suppliers to provide the Zone I Wellhead Protection radius, as calculated by the method outlined in the Pennsylvania Department of Environmental Protection Wellhead Protection regulations, for any public water supply well within 400 feet of the site. In addition to the setback distances specified in Section 925.15J and 925.15K, infiltration is prohibited in the Zone I radius as defined and substantiated by the Public Water Supplier in writing. If the applicant does not receive a response from the Public Water Supplier, the Zone I radius is assumed to be 100 feet.

T. The volume and rate of the net increase in stormwater runoff from the Regulated
Activities must be managed to prevent the physical degradation of receiving waters
from such effects as scour and streambank destabilization, to satisfy State Water
Quality Requirements, by controlling the 2-year post-development runoff to a 30%
Release Rate.

U. The municipality may, after consultation with DEP, approve alternative methods for
meeting the State Water Quality Requirements other than those in this Section, provided that they meet the minimum requirements of and do not conflict with State
law including but not limited to the Clean Streams Law.

925.16 STORMWATER MANAGEMENT DISTRICTS

A. Mapping of Stormwater Management Districts - To implement the provisions of the Catasauqua Creek and Lehigh River Sub-Basin 4, Monocacy, Nancy Run and Saucon Creek Watershed Stormwater Management Plans, the City is hereby divided into Stormwater Management Districts consistent with the Lehigh, Monocacy, Nancy Run and Saucon Creek Release Rate Maps presented in the Plans. The boundaries of the Stormwater Management Districts are shown on an official map which is available for inspection at the City Engineer’s office.

B. Description of Stormwater Management Districts - Two types of Stormwater
Management Districts may be applicable to the municipality, namely
Conditional/Provisional No Detention Districts and Dual Release Rate Districts as
described below.

1. Conditional/Provisional No Detention Districts - Within these districts, the
capacity of the “local” runoff conveyance facilities (as defined in Section 2)
must be calculated to determine if adequate capacity exists. For this
determination, the developer must calculate peak flows assuming that the site is
developed as proposed and that the remainder of the local watershed is in the
existing condition. The developer must also calculate peak flows assuming that
the entire local watershed is developed per current zoning and that all new
development would use the runoff controls specified by this Ordinance. The
larger of the two peak flows calculated will be used in determining if adequate
capacity exists. If adequate capacity exists to safely transport runoff from the
site to the main channel (as defined in Article 2), these watershed areas may
discharge post-development peak runoff without detention facilities. If the
capacity calculations show that the “local” runoff conveyance facilities lack
adequate capacity, the developer shall either use a 100% release rate control or
provide increased capacity of downstream elements to convey increased peak
flows consistent with Section 925.17P. Any capacity improvements must be
designed to convey runoff from development of all areas tributary to the
improvement consistent with the capacity criteria specified in Section 306.D.
By definition, a storm drainage problem area associated with the “local” runoff
conveyance facilities indicates that adequate capacity does not exist. Sites in
these districts are still required to meet all of the water quality requirements in
Section 304.

2. Dual Release Rate Districts - Within these districts, the 2-year post-development
peak discharge must be controlled to 30% of the pre-development
2-year runoff peak. Further, the 10-year, 25-year and 100-year postdevelopment
peak runoff must be controlled to the stated percentage of the predevelopment
peak. Release Rates associated with the 10- through 100-year
events vary from 50% to 100% depending upon location in the watershed. [For
the Monocacy Creek and Nancy Run Watersheds, the original Single Release
Rate Districts become Dual Release Rate Districts due to the channel protection
standard requiring developments to meet a 2-year 30% Release Rate.]

925.17. STORMWATER MANAGEMENT DISTRICT IMPLEMENTATION PROVISIONS

A. Applicants shall provide a comparative pre- and post-construction stormwater management hydrograph analysis for each direction of discharge and for the site overall to demonstrate compliance with the provisions of this Ordinance.

B. Any stormwater management controls required by this Ordinance and subject to a dual release rate criteria shall meet the applicable release rate criteria for each of the 2-, 10-, 25- and 100-year return period runoff events consistent with the calculation methodology specified in Section 925.18.

C. The exact location of the Stormwater Management District boundaries as they apply to a given development site shall be determined by mapping the boundaries using the two-foot topographic contours provided as part of the Drainage Plan. The District boundaries as originally drawn coincide with topographic divides or, in certain instances, are drawn from the intersection of the watercourse and a physical feature such as the confluence with another watercourse or a potential flow obstruction (e.g. road, culvert, bridge, etc.). The physical feature is the downstream limit of the subarea and the subarea boundary is drawn from that point up slope to each topographic divide along the path perpendicular to the contour lines.

D. Any downstream capacity analysis conducted in accordance with this Ordinance shall use the following criteria for determining adequacy for accepting increased peak flow rates:

1. Natural or man-made channels or swales must be able to convey the increased runoff associated with a 2-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 most current DEP Erosion and Sediment Pollution Control Program Manual. Permissible velocities from the DEP manual for selected channels are presented in Appendix C of this Ordinance.

2. Natural or man-made channels or swales must be able to convey the increased 25-year return period runoff without creating any hazard to persons or property. A one hundred (100) year design storm is required where a storm of this return period would likely cause damage to existing or future structures or their contents were it not for implementation of proper storm water management provisions.

3. Culverts, bridges, storm sewers or any other facilities which must pass or convey flows from the tributary area must be designed in accordance with DEP Chapter 105 regulations (if applicable) and, at minimum, pass the increased 25-year return period runoff.

E. For a proposed development site located within one release rate category subarea, the total runoff from the site shall meet the applicable release rate criteria. For development sites with multiple directions of runoff discharge, individual drainage directions may be designed for up to a 100% release rate so long as the total runoff from the site is controlled to the applicable release rate.

F. For a proposed development site located within two or more release category subareas, the peak discharge rate from any subarea shall be the pre-development peak discharge for that subarea multiplied by the applicable release rate. The calculated peak discharges shall apply regardless of whether the grading plan changes the drainage area by subarea. An exception to the above may be granted if discharges from multiple subareas re-combine in proximity to the site. In this case, peak discharge in any direction may be a 100% release rate provided that the overall site discharge meets the weighted average release rate.

G. For a proposed development site located partially within a release rate category subarea and partially within a Conditional/Provisional No Detention subarea, the size of the pre-development drainage area on a site may not be changed post-development to create potentially adverse conditions on downstream properties except as part of a “No Harm” or Hardship waiver procedure.

H. No portion of a site may be regraded between adjacent watershed(s) except as part of a “No Harm” or Hardship Waiver procedure.

I. Within a release rate category area, for a proposed development site which has areas which drain to a closed depression(s), the design release from the site will be the lesser of (a) the applicable release rate flow assuming no closed depression(s) or (b) the existing peak flow actually leaving the site. In cases where (b) would result in an unreasonably small design release, the design discharge of less than or equal to the release rate will be determined by the available downstream conveyance capacity to the main channel calculated using Section 925.17D and the minimum orifice criteria.

J. Off-site areas which 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 using the capacity criteria in Section 925.17D and the detention criteria in Section 925.18.

K. For development sites proposed to take place in phases, all detention ponds shall be designed to meet the applicable release rate(s) applied to all site areas tributary to the proposed pond discharge direction. All site tributary areas will be assumed as developed, regardless of whether all site tributary acres are proposed for development at that time. An exception shall be sites with multiple detention ponds in series where only the downstream pond must be designed to the stated release rate.

L. Where the site area to be impacted by a proposed development activity differs significantly from the total site area, only the proposed impact area shall be subject to the release rate criteria. The impact area includes any proposed cover or grading changes.

M. Development proposals which, through groundwater recharge or other means, do not increase either the rate or volume of runoff discharged from the site compared to pre-development are not subject to the release rate provisions of this Ordinance.

N. “No Harm” Water Quantity Option - For any proposed development site not located in a conditional no detention district, the developer has the option of using a less restrictive runoff control (including no detention) if the developer can prove that special circumstances exist for the proposed development site and that “no harm” would be caused by discharging at a higher runoff rate than that specified by the Plan. Special circumstances are defined as any hydrologic or hydraulic aspects of the development itself not specifically considered in the development of the Plan runoff control strategy. Proof of “no harm” would have to be shown from the development site through the remainder of the downstream drainage network to the confluence of the creek with the Lehigh River. Proof of “no harm” must be shown using the capacity criteria specified in Section 925.17D if downstream capacity analysis is a part of the “no harm” justification.

Attempts to prove “no harm” based upon downstream peak flow versus capacity analysis shall be governed by the following provisions:

1. The peak flow values to be used for downstream areas for the design return period storms (2-, 10-, 25- and 100-year) shall be the values from the calibrated WATERSHED Models or as calculated by an applicant using an alternate method acceptable to the municipality. The flow values from the WATERSHED Model would be supplied to the developer by the municipality upon request.

2. Any available capacity in the downstream conveyance system as documented by a developer may be used by the developer only in proportion to his development site acreage relative to the total upstream undeveloped acreage from the identified capacity (i.e. if his site is 10% of the upstream undeveloped acreage, he may use up to 10% of the documented downstream available capacity).

3. Developer-proposed runoff controls which would generate increased peak flow rates at storm drainage problem areas would, by definition, be precluded from successful attempts to prove “no harm”, except in conjunction with proposed capacity improvements for the problem areas consistent with Section 925.17P.

Any “no harm” justifications shall be submitted by the developer to the Lehigh Valley Planning Commission and the City Engineer for review as part of the Drainage Plan submission per Section 3. Any extra submission costs resulting from the dual submission and review shall be borne by the developer. The developer completely assumes all risks in so much that the submission of “no harm” requires a rigorous review for its approval and this approval is not guaranteed.

O. 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 based on the required release rate at the point of discharge. Peak runoff rates of discharge from a regional detention basin shall be based upon maintaining existing peak runoff rates for the tributary area, except that other criteria for discharge may apply for regional detention facilities located within a watershed with a county approved Act 167 Storm Water Management Plan. Any developer relying upon regional detention facilities in lieu of on-site controls shall pay an appropriate fee to the owner of the regional facility. Any proposed regional detention facility shall have the approval of the Lehigh Valley Planning Commission as well as the City Engineer.

P. Capacity Improvements - In certain instances, primarily within the Conditional/Provisional No Detention areas, 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 could 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. Peak flow calculations shall be done assuming that the local watershed is in the existing condition and then assuming that the local watershed is developed per current zoning and using the specified runoff controls. Any capacity improvements would be designed using the larger of the above peak flows and the capacity criteria specified in Section 925.17D. All new development in 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.

Capacity improvements may also be provided as necessary to implement any regional detention alternatives or to implement a modified “no harm” option which proposes specific capacity improvements to provide that a less stringent discharge control would not create any harm downstream.

925.18 CALCULATION METHODOLOGY

A. Stormwater runoff from all development sites shall be calculated using either the rational method or the soil-cover-complex methodology. Complete detailed drainage calculations and applicable charts and nomographs certified (i.e. P.E. Stamp) by the design engineer shall be submitted to the City Engineer.

B. Infiltration BMP loading rate percentages in the Recommendation Chart for Infiltration Stormwater Management BMPs in Carbonate Bedrock in Appendix D shall be calculated as follows:

The area tributary to the infiltration BMP shall be weighted as follows:
All disturbed areas to be made impervious: weight at 100%
All disturbed areas to be made pervious: weight at 50%
All undisturbed pervious areas: weight at 0%
All existing impervious areas: weight at 100%

C. Soil thickness is to be measured from the bottom of any proposed infiltration system. The effective soil thickness in the Recommendation Chart for Infiltration Stormwater Management BMPs in Carbonate Bedrock in Appendix D is the measured soil thickness multiplied by the thickness factor based on soil permeability (as measured by the adapted 25 PA Code 73.15. percolation test in Appendix G), as follows:

PERMEABILITY RANGE* THICKNESS FACTOR
6.0 to 12.0 inches/hour 0.8
2.0 to 6.0 inches/hour 1.0
1.0 to 2.0 inches/hour 1.4
0.75 to 1.0 inches/hour 1.2
0.5 to 0.75 inches/hour 1.0
*If the permeability rate (as measured by the adapted 25 PA Code 73.15. percolation test in Appendix G) falls on a break between two thickness factors, the smaller thickness factor shall be used.

Sites with soil permeability greater than 12.0 in./hr. or less than 0.5 in./hr., as measured by the adapted 25 PA Code 73.15. percolation test in Appendix G, are not recommended for infiltration.

D. The design of any detention basin intended to meet the requirements of this Ordinance shall be verified by routing the design storm hydrograph through the proposed basin using the storage indication method or other methodology demonstrated to be more appropriate. For basins designed using the rational method technique, the design hydrograph for routing shall be either the Universal Rational Hydrograph or the modified rational method trapezoidal hydrograph which maximizes detention volume. Use of the Modified Rational hydrograph shall be consistent with the procedure described in Section “PIPERAT” of the Users’ Manual for the Penn State Urban Hydrology Model (1987).

Detention ponds shall be designed so that they return to normal conditions within approximately twelve (12) hours after the termination of the storm, unless the City Engineer finds that downstream conditions may warrant other design criteria for storm water release. (See Appendix ‘A’ – Stormwater Design Standards)

The developer shall demonstrate that such ponds are designed, protected and located to assure that public safety is maximized and health problems are prevented. Certain protective devices and/or screenings such as fencing and landscaping may be required at the discretion of the City Engineer or Planning Commission. The depth of the facility in conjunction with the surrounding structures shall be taken into account when considering the need for the above improvements.

The developer shall verify that the operation of the detention facilities will not aggravate potential downstream peaking conditions, unless the detention facilities have been designed in accordance with an approved Act 167 Storm Water Management Plan for the applicable watershed.

E. BMPs designed to store or infiltrate runoff and discharge to surface runoff or pipe flow shall be routed using the storage indication method.

F. BMPs designed to store or infiltrate runoff and discharge to surface runoff or pipe flow shall provide storage volume for the full WQv below the lowest outlet invert.

G. Wet Detention Ponds designed to have a permanent pool for the WQv shall assume that the permanent pool volume below the primary outlet is full at the beginning of design event routing for the purposes of evaluating peak outflows.

H. All stormwater detention facilities shall provide a minimum 1.0 foot freeboard above the maximum pool elevation associated with the 2- through 25-year runoff events. A 0.5 foot freeboard shall be provided above the maximum pool elevation of the 100-year runoff event. The freeboard shall be measured from the maximum pool elevation to the invert of the emergency spillway. The 2- through 100-year storm events shall be controlled by the primary outlet structure. An emergency spillway for each basin shall be designed to pass the 100-year return frequency storm peak basin inflow rate with a minimum 0.5 foot freeboard measured to the top of basin. The freeboard criteria shall be met considering any offsite areas tributary to the basin as developed, as applicable. If this detention facility is considered to be a dam as per DEP Chapter 105, the design of the facility must be consistent with the Chapter 105 regulations, and may be required to pass a storm greater than the 100-year event. The City Engineer may allow some relief from the freeboard requirements, depending upon construction methods and other extenuating circumstances.

I. The minimum circular orifice diameter for controlling discharge rates from detention facilities shall be three (3) inches. Designs where a lesser size orifice would be required to fully meet release rates shall be acceptable provided that as much of the site runoff as practical is directed to the detention facilities. The minimum 3 inch diameter does not apply to the control of the WQv.

J. Runoff calculations using the soil-cover-complex method shall use the Natural Resources Conservation Service Type II 24-hour rainfall distribution. The 24-hour rainfall depths for the various return periods to be used consistent with this Ordinance are taken from the PennDOT Intensity - Duration - Frequency Field Manual (May 1986) for Region 4:

Return Period 24-Hour Rainfall Depth
1 year 2.40 inches
2 year 3.00 inches
5 year 3.60 inches
10 year 4.56 inches
25 year 5.52 inches
50 year 6.48 inches
100 year 7.44 inches

A graphical and tabular presentation of the Type II-24 hour distribution is included in Appendix C.

K. Stormwater runoff from watersheds of one hundred (100) or less acres may be calculated using the Rational Method as described in the latest manual of the American Society of Civil Engineers. For the Rational Method use runoff coefficients, rainfall intensities consistent with appropriate times of concentration and return periods and the Intensity-Duration-Frequency Curves as presented in Appendix C and appropriate to this topic, as stated in the most up-to-date issue of the “Storm Water Design Policy Manual of the Department of Public Works.”

L. Stormwater runoff from watersheds of more than one hundred (100) acres shall be calculated using the soil-cover-complex method developed by the Soil Conservation Service or other appropriate method acceptable to the City Engineer.

All calculations using the soil-cover-complex method shall use the Soil Conservation Service Type II 24-hour rainfall distribution. The 24-hour rainfall depths for the various return periods shall be from the current issue of the PennDOT Intensity – Duration- Frequency field Manual for Region 4, as indicated in the most up-to-date issue of the “Storm Water Design Policy Manual of the Department of Public Works.”

Runoff Curve Numbers (CN’s) to be used in the soil-cover-complex method shall be based upon the matrix presented in Appendix C.

M. Runoff coefficients for use in the Rational Method shall be based upon the table presented in Appendix C.

N. All time of concentration calculations shall use a segmental approach which may include one or all of the flow types below:

1. Sheet Flow (overland flow) calculations shall use either the NRCS average velocity chart (Figure 3-1, Technical Release-55, 1975) or the modified kinematic wave travel time equation (equation 3-3, NRCS TR-55, June 1986). If using the modified kinematic wave travel time equation, the sheet flow length shall be limited to 50 feet for designs using the Rational Method and limited to 150 feet for designs using the Soil-Cover-Complex method.

2. Shallow Concentrated Flow travel times shall be determined from the watercourse slope, type of surface and the velocity from Figure 3-1 of TR-55, June 1986.

3. Open Channel Flow travel times shall be determined from velocities calculated by the Manning equation. Bankfull flows shall be used for determining velocities. Manning ‘n’ values shall be based on the table presented in Appendix C.

4. Pipe Flow travel times shall be determined from velocities calculated using the Manning equation assuming full flow and the Manning ‘n’ values from Appendix C.

O. If using the Rational Method, all pre-development calculations for a given discharge direction shall be based on a common time of concentration considering both on-site and any off-site drainage areas. If using the Rational Method, all post-development calculations for a given discharge direction shall be based on a common time of concentration considering both on-site and any off-site drainage areas.

P. The Manning equation shall be used to calculate the capacity of watercourses and storm sewers. Culverts shall be designed using standard engineering methods acceptable to the City Engineer. Manning ‘n’ values used in the calculations shall be consistent with the table presented in Appendix C.

Q. The Pennsylvania DEP, Chapter 105, Rules and Regulations, apply to the construction, modification, operation or maintenance of both existing and proposed dams, water obstructions and encroachments throughout the watershed. Criteria for design and construction of stormwater management facilities according to this Ordinance may not be the same criteria that are used in the permitting of dams under the Dam Safety Program.

SECTION 3
DRAINAGE PLAN REQUIREMENTS

925.19 GENERAL REQUIREMENTS

For any of the Regulated Activities of this Ordinance, prior to the final approval of subdivision and/or land development plans, or the issuance of any permit, or the commencement of any land disturbance activity, the owner, subdivider, developer or his agent shall submit a Drainage Plan and receive City approval of the Plan.

925.20 EXEMPTIONS

Exemptions from the Drainage Plan Requirements are as specified in Section 925.06.

925.21 DRAINAGE PLAN CONTENTS

The following items shall be included in the Drainage Plan:

A. General

1. General description of project.

2. General description of proposed permanent stormwater controls.

3. The name of the project site, the name and address of the owner of the property and the name of the individual or firm preparing the Drainage Plan.

B. Map(s) of the project area showing:

1. The location of the project relative to highways, municipalities or other identifiable landmarks.

2. Existing contours at intervals of two (2) feet. In areas of steep slopes (greater than 15%), five-foot contour intervals may be used. Off-site drainage areas impacting the project including topographic detail. Scale shall be 1”= 40’or 1”= 30’ or other scale acceptable to the City Engineer.

3. Streams, lakes, ponds or other bodies of water within the project area.

4. Other physical features including flood hazard boundaries, existing drainage swales, wetlands, closed depressions, sinkholes and areas of natural vegetation to be preserved.

5. Locations of proposed underground utilities, sewers and water lines. The locations of all existing and proposed utilities, sanitary sewers and water lines within 50 feet of property lines of the project site.

6. An overlay showing soil types and boundaries based on the Lehigh or Northampton County Soil Survey, as applicable, latest edition. Any hydric soils present on the site should be identified as such.

7. An overlay showing geologic types and boundaries .

8. Proposed changes to land surface and vegetative cover. Stormwater calculations shall show and quantify the area of additional impervious surfaces.

9. Proposed structures, roads, paved areas and buildings.

10. Final contours at intervals of two (2) feet. In areas of steep slopes (greater than 15%), five-foot contour intervals may be used.

11. Stormwater Management District boundaries applicable to the site.

12. Clear identification of the location and nature of permanent stormwater BMPs.

13. An adequate access easement around all stormwater BMPs that would provide City ingress to and egress from a public right-of-way.

14. A schematic showing all tributaries contributing flow to the site and all existing man-made features beyond the property boundary that would be affected by the project.

15. The location of all public water supply wells within 400 feet of the project and all private water supply wells within 100 feet of the project.

C. Stormwater management controls and BMPs

1. All stormwater management controls and BMPs shall be shown on a map and described, including:

a. Groundwater recharge methods such as seepage pits, beds or trenches. When these structures are used, the locations of septic tank infiltration areas and wells shall be shown.

b. Other control devices or methods such as roof-top storage, semi-pervious paving materials, grass swales, parking lot ponding, vegetated strips, detention or retention ponds, storm sewers, etc.

2. All calculations, assumptions and criteria used in the design of the BMPs shall be shown.

3. All site testing data used to determine the feasibility of infiltration on a site.

4. All details and specifications for the construction of the stormwater
management controls and BMPs.

C. The BMP Operations and Management Plan, as required in Section 6, describing how
each permanent stormwater BMP will be operated and maintained and the identity of
the person(s) responsible for operations and maintenance. A statement must be
included, signed by the landowner, acknowledging that the stormwater BMPs are
fixtures that cannot be altered or removed without approval by the municipality.

D. An Environmental Resources Site Design Assessment that describes the following:

1. The extent to which the proposed grading and impervious cover avoid
disturbance of significant environmental resources and preserve existing site
hydrology.

2. An assessment of whether alternative grading and impervious cover site design
could lessen the disturbance of significant environmental resources and/or make
better use of the site hydrologic resources.

3. A description of how the proposed stormwater management controls and BMPs
serve to mitigate any adverse impacts on environmental resources on the site.

Significant environmental resources considered in the site design assessment include, but are not limited to, steep slopes, ponds, lakes, streams, wetlands, hydric soils, floodplains, riparian vegetation, native vegetation and special geologic features.

925.22 PLAN SUBMISSION

A. For Regulated Activities specified in Sections 925.05A and 925.05B:

1.