Source: http://www.ecode360.com/10223961
Timestamp: 2017-09-23 07:20:00
Document Index: 613671558

Matched Legal Cases: ['§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', 'art 630', '§ 203', 'art 630', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', 'art 630', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', 'art 630', 'art 650', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203', '§ 203']

Township of Hamilton, NJ Stormwater Management
Ch 203 Art XXV Stormwater Management
§ 203-261 Scope and purpose; applicability.
§ 203-262 Site development stormwater plans.
§ 203-263 Methodologies for calculation of stormwater runoff rate and volume, stormwater runoff quality, and groundwater recharge.
§ 203-264 Stormwater management performance standards for major development.
§ 203-265 Design, construction, and safety standards for structural stormwater management measures.
§ 203-266 Inspection, maintenance and repair of stormwater management measures.
§ 203-267 Definitions.
§ 203-268 Violations and penalties.
§ 203-269 Appendices.
§ 203-270 Additional sources for technical guidance.
§ 203-271 Stormwater Landscape Illustrations, Appendix A; Appendix B.
Article XXV: Stormwater Management
[Added 5-21-2007 by Ord. No. 1593-2007]
Chapter 203: Land Use and Development Article XXV Stormwater Management
Increases of stormwater runoff, soil erosion and nonpoint source pollutants have occurred in the past as a result of land development, and contribute to the degradation of the water resources of the Township of Hamilton.
Certain lands of the Township of Hamilton lie within the Pinelands Area, and therefore, development in this portion of the Township of Hamilton is subject to the requirements of the Pinelands Protection Act (N.J.S.A. 13:18A-1 et seq.) and the implementing regulations and minimum standards contained in the Pinelands Comprehensive Management Plan (N.J.A.C. 7:50-1.1 et seq.) (CMP). The purpose and intent of these regulations and standards is to promote orderly development of the Pinelands so as to preserve and protect the significant and unique natural, ecological, agricultural, archaeological, historical, scenic, cultural and recreational resources of the Pinelands.
Pinelands Area resources are to be protected in accordance with the Pinelands Comprehensive Management Plan at N.J.A.C. 7:50 et seq., New Jersey's Stormwater Management Rules at N.J.A.C. 7:8-1.1 et seq. and New Jersey's surface water quality antidegradation policies contained in the New Jersey Surface Water Quality Standards at N.J.A.C. 7:9B-1.1 et seq. Permitted uses shall maintain the ecological character and quality of the Pinelands, including good water quality and natural rates and volumes of flow.
Increased stormwater rates and volumes and the sediments and pollutants associated with stormwater runoff from future development projects have the potential to adversely affect the Township of Hamilton's streams and water resources and the streams and water resources of downstream municipalities.
It is in the public interest to regulate the discharge of stormwater runoff from major development projects, as defined in § 203-267 of this article, in order to control and minimize increases in stormwater runoff rates and volumes, to maintain groundwater recharge, and to control and minimize soil erosion, stream channel erosion and nonpoint source pollution associated with stormwater runoff.
Therefore, it is the purpose of this article to establish minimum stormwater management requirements and controls for major development, consistent with the statewide stormwater requirements at N.J.A.C. 7:8, the regulations and standards contained in the Pinelands CMP, and the provisions of the adopted master plan and land use ordinances of the Township of Hamilton.
Through this article, the Township of Hamilton has established the following goals for stormwater control:
To restore, protect, maintain and enhance the quality of the streams and water resources of the Township of Hamilton and the ecological character and quality of the Pinelands Area;
To minimize pollutants in stormwater runoff from new and existing development in order to restore, protect, enhance and maintain the chemical, physical and biological integrity of the surface and groundwaters of the Township of Hamilton, to protect public health and to enhance the domestic, municipal, recreational, industrial and other uses of water;
To protect public safety through the proper design and operation of stormwater management basins; and
To encourage the use of drainage facilities and vegetated buffer zones as open space, recreation and conservation areas.
In order to achieve the goals for stormwater control set forth in this article, the Township of Hamilton has identified the following management techniques:
Compliance with the stormwater runoff quantity and rate, groundwater recharge, erosion control, and stormwater runoff quality standards established through N.J.A.C. 7:8-1.1 et seq., and this article, shall be accomplished to the maximum extent practicable through the use of nonstructural BMPs, before relying on structural BMPs. Nonstructural BMPs are also known as "low-impact development (LID) techniques.
This article shall apply to all site plans and subdivisions for major developments that require preliminary or final site plan or subdivision review; and
All major development projects undertaken by the Township of Hamilton shall comply with this article.
Procedures. In addition to other development review procedures set forth in the Code of the Township of Hamilton, major developments shall comply with the stormwater management requirements and specifications set forth in this article. New agricultural development that meets the definition of major development in § 203-267 of this article shall be submitted to the appropriate Soil Conservation District for review and approval in accordance with the requirements of N.J.A.C. 7:8-5.4(b).
Natural watercourses should not be dredged, cleared of vegetation, deepened, widened, straightened, stabilized or otherwise altered without a stream encroachment permit from the New Jersey Department of Environmental Protection, Division of Water Resources, Bureau of Flood Plain Management.
In their interpretation and application, the provisions of this article shall be held to be the minimum requirements for the promotion of the public health, safety, and general welfare. This article is not intended to interfere with, abrogate, or annul any other ordinances, rule or regulation, statute, or other provision of law, except that where any provision of this article imposes restrictions different from those imposed by any other ordinance, rule or regulation, or other provision of law, the more restrictive or stringent provisions or higher standards shall control.
In the event that a regional stormwater management plan(s) is prepared and formally adopted pursuant to N.J.A.C. 7:8-1.1 et seq. for any drainage area(s) or watershed(s) of which the Township of Hamilton is a part, the stormwater provisions of such a plan(s) shall be adopted by the Township of Hamilton within one year of the adoption of a Regional Stormwater Management Plan (RSWMP) as an amendment to an Areawide Water Quality Management Plan. Local ordinances proposed to implement the RSWMP shall be submitted to the Commission for certification within six months of the adoption of the RSWMP per N.J.A.C. 7:8 and the Pinelands CMP (N.J.A.C. 7:50).
Whenever an applicant seeks municipal approval of a site development that is subject to this article, the applicant shall submit all of the required components of the checklist for the site development stormwater plan at Subsection C below as part of the applicant's application for subdivision or site plan approval. These required components are in addition to any other information required under any provisions of the Township of Hamilton's land use ordinance or by the Pinelands Commission pursuant to N.J.A.C. 7:50-1.1 et seq.
Any application for approval of a major development shall include at least the following information. All required engineering plans shall be submitted to the Township of Hamilton and the Pinelands Commission, if located within the Pinelands Area, in CAD Format 2000 or higher, registered and rectified to NJ State Plane Feet NAD 83 or Shape Format NJ State Plane Feet NAD 83, and all other documents shall be submitted in both paper and commonly used electronic file formats such as .pdf, word processing, database or spreadsheet files. Three copies of each item shall be submitted.
Topographic base map. The applicant shall submit a topographic base map of the site which extends a minimum of 300 feet beyond the limits of the proposed development, at a scale of one inch equals 200 feet or greater, showing one-foot contour intervals. The map shall indicate the following: existing surface water drainage, shorelines, steep slopes, soils, highly erodible soils, perennial or intermittent streams that drain into or upstream of any Category One or Pinelands waters, wetlands and floodplains along with their appropriate buffer strips, marshlands and other wetlands, pervious or vegetative surfaces, existing surface and subsurface human-made structures, roads, bearing and distances of property lines, and significant natural and man-made features not otherwise shown. The Township of Hamilton or the Pinelands Commission, if applicable, may require upstream tributary drainage system information as necessary.
Detailed soil and other environmental conditions on the portion of the site proposed for installation of any stormwater BMPs, including, at a minimum: soils report based on on-site soil tests; locations and spot elevations, in plan view, of test pits and permeability tests; permeability test data and calculations; and any other required soil data (e.g., mounding analyses results) correlated with location and elevation of each test site; cross-section of proposed stormwater BMP with side-by-side depiction of soil profile drawn to scale and seasonal high water table elevation identified; and any other information necessary to demonstrate the suitability of the specific proposed structural and nonstructural stormwater management measures relative to the environmental conditions on the portion(s) of the site proposed for implementation of those measures.
The applicant shall submit a detailed land use planning and source control plan which provides a description of how the site will be developed to meet the erosion control, groundwater recharge and stormwater runoff quantity and quality standards at § 203-264 through use of nonstructural or low-impact development techniques and source controls to the maximum extent practicable before relying on structural BMPs. The land use planning and source control plan shall include a detailed narrative and associated illustrative maps and/or plans that specifically address how each of the following nine nonstructural strategies identified in Subchapter 5 of the NJDEP Stormwater Management Rules (N.J.A.C. 7:8-5) and set forth below {Subsection C(1)(d)[1][a] through [i]} will be implemented to the maximum extent practicable to meet the standards at § 203-264 of this article on the site. If one or more of the nine nonstructural strategies will not be implemented on the site, the applicant shall provide a detailed rationale establishing a basis for the contention that use of the strategy is not practicable on the site.
For sites where stormwater will be generated from high pollutant loading areas or where stormwater will be exposed to source material, as defined in § 203-267 of this article, the applicant shall also demonstrate in the land use planning and source control plan that the requirements of § 203-264 have been met.
The use of nonstructural strategies to meet the performance standards in § 203-264 of this article is not required for development sites creating less than one acre of disturbance. However, if the project is within the Pinelands Area, each application for major development that requires a landscaping plan shall contain a landscaping or revegetation plan in accordance with the CMP standards at N.J.A.C. 7:50-6.24(c). In addition, the applicant shall demonstrate that, at a minimum, existing trees and vegetation on the development site will be preserved and protected according to the minimum standards established by provisions of the Township of Hamilton Land Use Ordinance, Zoning Ordinance or by conditions of zoning or variance approval.
Calculations (groundwater recharge and stormwater runoff rate, volume and quality). The applicant shall submit comprehensive hydrologic and hydraulic design calculations for the predevelopment and post-development conditions for the design storms specified in § 203-263. The standards for groundwater recharge and stormwater runoff rate, volume and quality required by § 203-264 shall be met using the methods, calculations and assumptions provided in § 203-263.
Inspection, maintenance and repair plan. The applicant shall submit a detailed plan describing how the proposed stormwater management measure(s) shall meet the maintenance and repair requirements of § 203-266 of this article. Said plan shall include, at a minimum, the following elements:
Exception from submission requirements. An exception may be granted from submission of any of these required components [except Subsection C(1)(g) above, inspection, maintenance, and repair plan] if its absence will not materially affect the review process. However, for sites located within the Pinelands Area, items required pursuant to the application requirements in the Pinelands CMP [N.J.A.C. 7:50-4.2(b)] shall be submitted to the NJ Pinelands Commission unless the Executive Director waives or modifies the application requirements.
In complying with the stormwater runoff quantity and rate standards in § 203-264B, the design engineer shall calculate the stormwater runoff rate and volume using the USDA Natural Resources Conservation Service (NRCS) Runoff Equation, Runoff Curve Numbers, and Dimensionless Unit Hydrograph, as described in the NRCS National Engineering Handbook Part 630 — Hydrology and Technical Release 55 — Urban Hydrology for Small Watersheds, incorporated herein by reference, as amended and supplemented. Alternative methods of calculation may be utilized, provided such alternative methods are at least as protective as the NRCS methodology when considered on a regional stormwater management basis.
In complying with the stormwater runoff quality standards in § 203-264F(1), the design engineer shall calculate the stormwater runoff rate and volume using the USDA Natural Resources Conservation Service (NRCS) Runoff Equation, Runoff Curve Numbers, and Dimensionless Unit Hydrograph, as described in the NRCS National Engineering Handbook Part 630 - Hydrology and Technical Release 55 - Urban Hydrology for Small Watersheds, as amended and supplemented.
R = A + B - (A x B)/100, where:
For purposes of TSS reduction calculations, Table 2 presents the presumed removal rates for certain BMPs designed in accordance with the New Jersey BMP Manual. The BMP Manual may be obtained from the address identified in § 203-270A or found on the NJDEP's website at www.njstormwater.org. TSS reduction shall be calculated based on the removal rates for the BMPs in Table 2
Alternative stormwater management measures, removal rates and methods of calculating removal rates may be used if the design engineer provides documentation demonstrating the capability of these alternative rates and methods to the Township of Hamilton. Any alternative stormwater management measure, removal rate or method of calculating the removal rate shall be subject to approval by the Township of Hamilton and a copy shall be provided to the following:
The Division of Watershed Management, New Jersey Department of Environmental Protection, P.O. Box 418, Trenton, NJ 08625-0418; and
The New Jersey Pinelands Commission, P.O. Box 7, New Lisbon, NJ 08064, if the site is located within the Pinelands area.
Source: 7:8-5.5(c) and New Jersey BMP Manual Chapter 4
Total Phosphorous Percent Removal Rate
40% to 60% (final rate based upon detention time; see New Jersey BMP Manual, Chap. 9)
Pollutant removal rates as certified by NJDEP; see § 203-263
80% (porous paving)
80% (permeable pavers with storage bed)
60% (turf grass)
70% (native grasses, meadow and planted woods)
80% (indigenous woods)
50% to 90% (final rate based upon pool volume and detention time; see NJ BMP Manual)
Nutrient removal rates for stormwater BMPs. For purposes of post-development nutrient load reduction calculations, Table 2 presents the presumed removal rates for certain BMPs designed in accordance with the New Jersey BMP Manual. If alternative stormwater BMPs are proposed, the applicant shall demonstrate that the selected BMPs will achieve the nutrient removal standard required in § 203-264F.
In complying with the groundwater recharge requirements in § 203-264C(1)(a), the design engineer may calculate groundwater recharge in accordance with the New Jersey Groundwater Recharge Spreadsheet (NJGRS) computer program incorporated herein by reference as amended and supplemented. Information regarding the methodology is available in § 203-269A or from the New Jersey BMP Manual.
In complying with the groundwater recharge requirements in § 203-264C(1)(b), the design engineer shall:
Calculate stormwater runoff volumes in accordance with the USDA Natural Resources Conservation Service (NRCS) methodology, including the NRCS Runoff Equation and Runoff Curve Numbers, as described in the NRCS National Engineering Handbook Part 630 — Hydrology and Technical Release 55 — Urban Hydrology for Small Watersheds as amended and supplemented; and
To the maximum extent practicable, the performance standards in this section for major development shall be met by incorporating the nine nonstructural strategies identified in Subchapter 5 of the NJ Stormwater Management Rules (N.J.A.C. 7:8-5), and set forth in § 203-262C(1)(d)[1], into the design. The applicant shall identify within the land use planning and source control plan required by § 203-262C(1)(d) of this article how each of the nine nonstructural measures will be incorporated into the design of the project to the maximum extent practicable.
If the applicant contends that it is not practical for engineering, environmental or safety reasons to incorporate any of the nine nonstructural strategies into the design of a particular project, the applicant shall provide a detailed rationale establishing a basis for the contention that use of the strategy is not practical on the site. This rationale shall be submitted in accordance with the checklist requirements established by § 203-262 to the Township of Hamilton. A determination by the Township of Hamilton that this rationale is inadequate or without merit shall result in a denial of the application unless one of the following conditions is met:
The land use planning and source control plan is amended to include a description of how all nine nonstructural measures will be implemented on the development site, and the amended plan is approved by the Township of Hamilton;
The land use planning and source control plan is amended to provide an alternative nonstructural strategy or measure that is not included in the list of nine nonstructural measures, but still meets the performance standards in § 203-264, and the amended plan is approved by the Township of Hamilton; or
The land use planning and source control plan is amended to provide an adequate rationale for the contention that use of the particular strategy is not practical on the site, and the amended plan is approved by the Township of Hamilton.
In addition to all other requirements of this section, each applicant shall demonstrate that, at a minimum, existing trees and vegetation on the development site will be preserved, protected and maintained according to the minimum standards established by provisions of the Township of Hamilton Land Use Ordinance, Zoning Ordinance or by conditions of zoning or variance approval. Existing trees and vegetation shall be protected during construction activities in accordance with the Standard for Tree Protection During Construction provided in the NJ State Soil Conservation Committee Standards for Soil Erosion and Sediment Control in New Jersey, which is incorporated herein by reference as amended and supplemented. Vegetated buffer strips should be created or, where practicable, retained in their natural state along the banks of all watercourses, water bodies or wetlands. The width of the buffer should be sufficient to prevent erosion, trap the sediment carried with overland runoff, provide access to the water body and allow for periodic flooding without damage to structures. If there is no natural vegetated buffer, if the vegetated buffer strip cannot be retained or the buffer is damaged or altered during construction activities, the buffer shall be recreated pursuant to the following design standards. Plant materials specified for vegetated buffer strips should reference the use of native shrubs and trees, as required in the Pinelands Comprehensive Management Plan (CMP) at N.J.A.C. 7:50-6.24, and with common plant names identified at N.J.A.C. 7:50-6.25. Per every 1,500 square feet of applicable buffer area, the following plant material shall be installed:
[Amended 5-4-2009 by Ord. No. 1647-2009]
One deciduous canopy tree, two inches to 2 1/2 inches caliper.
Two ornamental trees, eight feet to 10 feet.
Three evergreen trees, six feet to eight feet.
Eight shrubs.
Area shall be seeded with native grass seed or meadow mix.
Mulch, as needed, to stabilize planting and retain soil.
In addition to all other requirements of this section, each application for major development within the Pinelands Area that requires a landscaping plan shall contain a landscaping or revegetation plan in accordance with the Pinelands CMP standards at N.J.A.C. 7:50-6.24(c).
Any land area used as a nonstructural stormwater management measure to meet the performance standards in § 203-264 shall be dedicated to a government entity; shall be subjected to a conservation easement filed with the appropriate County Clerk's office; or shall be subjected to an equivalent form of restriction approved by the Township of Hamilton that ensures that that measure, or an equivalent stormwater management measure, is maintained in perpetuity, as detailed in § 203-266 of this article.
Guidance for nonstructural stormwater management strategies is available in the New Jersey BMP Manual, which may be obtained from the address identified in § 203-270A or found on the NJDEP's website at www.njstormwater.org.
Exception for major development sites creating less than one acre of disturbance. The use of nonstructural strategies to meet the performance standards in § 203-264 of this article is not required for major development creating less than one acre of disturbance. However, the following requirements shall be met:
Each application for major development in the Pinelands Area that requires a landscaping plan shall contain a landscaping or revegetation plan prepared in accordance with the Pinelands CMP standards [N.J.A.C. 7:50-6.24(c)];
Each applicant shall demonstrate that, at a minimum, existing trees and vegetation on the development site will be preserved and protected according to the minimum standards established by provisions of the Township of Hamilton Land Use Ordinance, Zoning Ordinance or by conditions of zoning or variance approval; and
Existing trees and vegetation shall be protected during construction activities in accordance with the Standard for Tree Protection During Construction provided in the NJ State Soil Conservation Committee Standards for Soil Erosion and Sediment Control in New Jersey, which is incorporated herein by reference as amended and supplemented.
For all major developments, the total runoff volume generated from the net increase in impervious surfaces by a ten-year, twenty-four-hour storm shall be retained and infiltrated on-site.
In addition, the design engineer, using the assumptions and factors for stormwater runoff and groundwater recharge calculations contained in § 203-263, shall either:
In tidal flood hazard areas, a stormwater runoff quantity analysis in accordance with Subsection B(4)(a), (b) and (c) above shall only be applied if the increased volume of stormwater runoff could increase flood damages below the point of discharge.
The standards for stormwater runoff quantity and rate required by this section shall be met using the methods, calculations and assumptions provided in § 203-263.
For all major developments, with the exception of those described in Subsection C(4), below, the design engineer, using the assumptions and factors for stormwater runoff and groundwater recharge calculations contained in § 203-263, shall either:
Demonstrate through hydrologic and hydraulic analysis that any increase in the project site's stormwater runoff volume for the two-year, twenty-four-hour storm from predeveloped to post-developed conditions is infiltrated on-site.
The standards for groundwater recharge required by this section shall be met using the methods, calculations and assumptions provided in § 203-263.
The preceding groundwater recharge standards shall not apply to sites that create less than one acre of disturbance.
There shall be no direct discharge of stormwater runoff from any point or nonpoint source to any wetland, wetland transition area or surface water body.
The standards for stormwater runoff quality required by this section shall be met using the methods, calculations, assumptions and pollutant removal rates provided in § 203-263.
The TSS reduction requirement in Subsection F(2) shall not apply to any stormwater runoff in a discharge regulated under a numeric effluent limitation for TSS imposed under the NJPDES rules (N.J.A.C. 7:14A) or in a discharge specifically exempt under a NJPDES permit from this requirement.
The stormwater runoff quantity and rate standards in Subsection B shall still be met for all major development sites.
This subsection applies to the following areas of a major development as defined in § 203-267 of this article:
For a major development in areas described in Subsection F(1)(a) or (1)(b) above, in addition to the infiltration requirements specified in Subsection B(2) and the groundwater recharge requirements specified in Subsection C, the applicant shall demonstrate in the land use planning and source control plan required in § 203-264C(1)(d) that the following requirements have been met:
The extent of the areas described in Subsection F(1)(a) and (1)(b) above have been minimized on the development site to the maximum extent practicable;
The stormwater runoff from the areas described in Subsection F(1)(a) and (1)(b) above is segregated to the maximum extent practicable from the stormwater runoff generated from the remainder of the site such that co-mingling of the stormwater runoff from the areas described in Subsection F(1)(a) and (1)(b) above and the remainder of the site will be minimized;
The amount of precipitation falling directly on the areas described in Subsection F(1)(a) and (1)(b) above is minimized to the maximum extent practicable by means of a canopy, roof or other similar structure that reduces the generation of stormwater runoff; and
The stormwater runoff from or co-mingled with the areas described in Subsection F(1)(a) and (1)(b) above for the water quality design storm, defined in § 203-263B, Table 1, shall be subject to pretreatment by one or more of the following stormwater BMPs, designed in accordance with the New Jersey BMP Manual to provide 90% TSS removal:
Wet ponds which shall be hydraulically disconnected by a minimum of two feet of vertical separation from the seasonal high water table and shall be designed to achieve a minimum 80% TSS removal rate;
Media filtration system manufactured treatment device with a minimum 80% TSS removal as verified by the New Jersey Corporation for Advanced Technology and as certified by NJDEP.
If the potential for contamination of stormwater runoff by petroleum products exists on-site, prior to being conveyed to the pretreatment BMP required in Subsection D(2)(d) above, the stormwater runoff from the areas described in Subsection F(1)(a) and (1)(b) above shall be conveyed through an oil/grease separator or other equivalent manufactured filtering device to remove the petroleum hydrocarbons. The applicant shall provide the reviewing agency with sufficient data to demonstrate acceptable performance of the device.
Threatened and endangered species and associated habitat standards. Stormwater management measures shall address the impacts of the development on habitat for threatened and endangered species, in accordance with N.J.A.C. 7:8-5.2(c), 7:50-6.27, and 7:50-6.33 and 34.
Exceptions from strict compliance from the groundwater recharge, stormwater runoff quantity, and stormwater runoff quality requirements established by this article may be granted, at the discretion of the Township of Hamilton, and subject to approval by the Pinelands Commission, if applicable, provided that all of the following conditions are met:
The exception is consistent with that allowed by the Township of Hamilton;
The Township of Hamilton has an adopted and effective municipal stormwater management plan in accordance with N.J.A.C. 7:8-4.4, which includes a mitigation plan in accordance with N.J.A.C. 7:8-4.2(c)11. At this time, no specific mitigation measures have been developed. Certification by the Pinelands Commission is pending. The mitigation plan shall identify what measures are necessary to offset the deficit created by granting the exception and the municipality shall submit a written report to the county review agency and the NJDEP describing the exception and the required mitigation. Guidance for developing municipal stormwater management plans, including mitigation plans, is available from the NJDEP, Division of Watershed Management, and the New Jersey BMP Manual.
For projects within the Pinelands Area, mitigation may be provided off-site, but within the Pinelands Area. Mitigation shall be within the same drainage area as the development site, and shall meet or exceed the equivalent recharge, quality or quantity performance standard which is lacking on the development site due to the exception; or
In lieu of the required mitigation, a monetary "in-lieu contribution" may be provided by the applicant to the Township of Hamilton in accordance with the following:
The amount of the in-lieu contribution shall be determined by the Township of Hamilton, but the maximum in-lieu contribution required shall be equivalent to the cost of implementing and maintaining the stormwater management measure(s) for which the exception is granted;
For projects within the Pinelands Area, the in-lieu contribution shall be used to fund an off-site stormwater control mitigation project(s) located within the Pinelands Area, and in any case shall fund projects within the same drainage area as the development site, and shall meet or exceed the equivalent recharge, quality or quantity performance standards which is lacking on the development site. Such mitigation project shall be identified by the Township of Hamilton in the Township of Hamilton's adopted municipal stormwater management plan. The stormwater control project to which the monetary contribution will be applied shall be identified by the Township of Hamilton at the time the exception is granted. The applicant shall amend the project description and site plan required in § 203-262C(3) to incorporate a description of both the standards for which an on-site exception is being granted and of the selected off-site mitigation project.
The Township of Hamilton shall expend the in-lieu contribution to implement the selected off-site mitigation project within five years from the date that payment is received. Should the Township of Hamilton fail to expend the in-lieu contribution within the required time frame, the mitigation option provided in Subsection H(1)(c)[3] of this section shall be void and the Township of Hamilton shall be prohibited from collecting in-lieu contributions.
For projects located within the Pinelands, an exception from strict compliance granted in accordance with Subsection H(1) above shall not constitute a waiver of strict compliance from the requirements of the Pinelands Comprehensive Management Plan at N.J.A.C. 7:50. An applicant should contact the Pinelands Commission to determine whether a waiver of strict compliance is also required in accordance with N.J.A.C. 7:50, Subchapter 4, Part V.
Stormwater management basin landscaping.
Stormwater management areas. Stormwater management areas include bioretention systems, constructed stormwater wetlands, detention and infiltration basins, drainage ditches and swales and wet ponds. Stormwater management areas shall be designed in accordance with the New Jersey Stormwater Best Management Practices Manual (BMP). Sensitively designed basins and soils can be a visually pleasing benefit to the health, welfare and safety of Hamilton Township residents. The general design concept of these areas should be to deemphasize their function, creating aesthetic landscape features.
The Township encourages, where possible, that stormwater management basins be designed to imitate naturalistic land forms with irregular perimeters that subtly blend into the surrounding topography. Where enclosures are required, fence alignments shall follow, as closely as possible, the configuration of the basin. Rectilinear fence alignments are to be avoided.
The area shall be graded creatively to blend into the surrounding landscape and the design of the site, i.e., provide an informal meandering edge with varying slopes and gentle berming in locations, emulating a natural parkland.
Location of plantings within stormwater management areas shall be as outlined within the New Jersey Stormwater Best Management Practices Manual, Chapter 7, "Landscaping."
Stormwater management areas shall be planted pursuant to the quantities and types listed for the landscape concepts as outlined in Subsection I(8) below. Additional shrub and herbaceous plant material should be planted in accordance with the New Jersey Stormwater Best Management Practices Manual, Chapter 7, "Landscaping." Special preference should be given to those species of trees and plants which have known pollutant-removal abilities.
A complete planting plan for stormwater management areas shall be submitted for review by and approval of the Township Landscape Architect.
All plant materials shall be species indigenous to the area as per New Jersey Stormwater Best Management Practices Manual, Chapter 7, "Landscaping." Plant materials shall be consistent with N.J.A.C. 7:50-6.24 of the Pinelands CMP and § 203-185A(4)(d) of the Township's Land Use Ordinance.
One of the following landscape concepts for stormwater detention areas or an alternative concept complying with the standards set forth herein or as approved by the Township shall be used:
Reforestation. This landscape treatment is appropriate for detention basins and drainage areas that are not highly visible or are adjacent to areas of mature woodlands, greenbelts or wetlands. It reverts the disturbed areas to a revegetated, stable, low-maintenance, natural landscape asset over time.
The area shall be graded creatively to blend into the surrounding landscape and imitate a natural depression with an irregular edge. This shall include gentle berming. Linear, geometric basins are unacceptable.
The quantity of trees to be planted on the interior of the basins shall be equal to the number of trees that would be necessary to cover the entire area, based upon a twenty-foot by twenty-foot grid to the high-water line or outflow elevation. Of this number, 10% shall be 2 1/2 inches to three inches caliper, 20% shall be one inch to two inches caliper and 70% shall be whips six feet to eight feet in height.
The trees shall be planted in groves and spaced five feet to 15 feet on center.
The ground plane shall be seeded with a naturalization, wildflower and/or meadow grass mix. The specific blend shall be approved by the Township Landscape Architect and shall comply with Pinelands and BMP requirements.
All woody and herbaceous plants shall be species indigenous to the area and/or tolerant of typical wet/dry floodplain conditions.
Planting shall not be located within 20 feet of low-flow channels to allow for maintenance.
The perimeter area (slopes above the high-water line) shall include shade trees (approximately 80 per 1,000 linear feet), evergreen trees (approximately 40 per 1,000 linear feet), ornamental trees and shrubs screening drainage structures and creating visual interest.
Provisions for emergency access as well as general maintenance of the basins shall be reviewed by the Township Engineer. Plantings shall be designed to disguise yet not hinder vehicular access.
Recreation/open space feature.
This landscape concept is appropriate in situations where a basin is the largest or only portion of open space in an area or is adjacent to existing open space and recreational open space is desired. It is also appropriate for smaller, highly visible basins where a visually pleasing open area is desired.
The objective in these situations is to integrate the area into the landscape using topography and plantings in order to complement the function of the area and to provide a visually interesting landscape feature and/or recreation space.
The area shall be graded creatively to blend into the surrounding landscape and imitate a natural depression with an irregular edge. This shall include gentle berming.
Provide perimeter plantings, including shade trees, formally or informally, evergreen trees to create and screen views and small trees and shrubs to provide a continuous landscape strip screening drainage structures and creating visual interest.
Integrate buffer plantings with perimeter plantings, where applicable.
The following are guidelines for plant quantities:
(per 1,000 linear feet)
To provide recreational open space, concentrate frequently flooded detention in basin area (five- to ten-year storm volume) and provide a gently sloping, less often flooded area (ten- to one-hundred-year storm volume) as a recreational open field space. Provide ball fields and/or open play areas integrated with plantings in a park-like manner.
At detention basins and wet basins and where fences are required, the following standards shall apply:
The perimeter of the basin shall be planted in a naturalistic manner with a combination of evergreen trees, shade trees and shrub massings. The minimum width of the basin perimeter landscaping shall be 10 feet. A minimum of 50% of all plantings are to be evergreen.
Perimeter basin landscape plantings shall meet the following minimum sizes:
2 inches caliper
2.5 to 3 feet high
Plantings shall be arranged to allow for maintenance access to all basin facilities.
All required basin perimeter plantings are to be located outside of the required fence enclosure.
Basins located in front yard areas are subject to all previously stated landscaping standards for stormwater management facilities, with the following additions:
Maximum basin depth shall be 24 inches.
Geometrically shaped basins are unacceptable.
Minimum width of plant massings shall be 10 feet.
Ornamental trees should be planted along the basin perimeter for visual interest.
Landscape plantings are to be encouraged along the slopes and bottom of detention basins and on the side slopes of retention basins above the high-water line. These plantings shall consist of herbaceous plants which are indigenous to the area and/or tolerant of typical wet/dry floodplain conditions.
Plantings shall not be located within 10 feet of low-flow channels and drainage structures to allow for maintenance.
Special landscape provisions.
Site disturbance shall be minimized and existing vegetation retained whenever possible.
Development shall follow the natural contours of the landscape whenever possible to minimize grading.
Any contiguous area of disturbance, not associated with the installation of a roadway, shall be limited to 20,000 square feet for residential development and to 100,000 square feet for any other types of development. Contiguous areas of disturbance shall be separated by at least 20 feet of area maintained at natural grade and retaining existing, mature vegetated cover.
Lawn- or grass-covered areas may comprise no more than 25% or 1/4 acre, whichever is greater of the total vegetated area.
Plants shall be selected based on consideration of site conditions and plant function. Low-maintenance design is encouraged. Use of drought-tolerant species, where applicable, is encouraged.
Structural stormwater management measures shall be designed to meet the standards established in this section. These standards have been developed to protect public safety, conserve natural features, create an aesthetically pleasing site and promote proper on-site stormwater management. The Township of Hamilton reserves the right to require existing basins that pose a health or safety hazard to be retrofitted to comply with the standards in this subsection.
The following structural stormwater management measures may be utilized as part of a stormwater management system at a major land development; provided that the applicant demonstrates that they are designed, constructed and maintained so as to meet the standards and requirements established by this article. If alternative stormwater management measures are proposed, the applicant shall demonstrate that the selected measures will achieve the standards established by this article.
For all stormwater management measures at a development site, each applicant shall submit a detailed inspection, maintenance and repair plan consistent with the requirements of § 203-266 of this article.
Use of natural, non-wetland wooded depressions for stormwater runoff storage; and
For projects within the Pinelands Area, establishment of attractive landscaping in and around the basin that mimics the existing vegetation and incorporates native Pinelands plants, including, but not limited to, the species listed in N.J.A.C. 7:50-6.25 and 6.26.
In both the Pinelands and other areas of the Township, the design of the facilities shall include, if practical, method of total drainage of basins for routine maintenance or basin failure. This system shall include a tamperproof locking device acceptable to the Township Engineer. Keys for the locking device shall be maintained by the Hamilton Township Public Works Department exclusively. The locking device shall be unlocked only for routine maintenance or emergency repairs. The applicant or developer shall enter into an agreement with the Township outlining the requirements and methods for maintenance or emergency drainage of the facility. This agreement shall be binding on both the developer and future owners of the system and shall be recorded in the Office of the Atlantic County Clerk. A standard form of agreement is on file with the Hamilton Township Planning Board Administrator.
After all construction activities and required field testing have been completed on the development site, as-built plans depicting design and as-built elevations of all stormwater management measures shall be prepared by a licensed land surveyor and submitted to the municipal engineer. Based upon the municipal engineer's review of the as-built plans, all corrections or remedial actions deemed by the municipal engineer to be necessary due to the failure to comply with the standards established by this article and/or any reasons of public health or safety shall be completed by the applicant. In lieu of review by the municipal engineer, the Township of Hamilton reserves the right to engage a professional engineer to review the as-built plans. The applicant shall pay all costs associated with such review.
A stormwater infiltration BMP shall be sited in suitable soils verified by field testing to have permeability rates between one inch and 20 inches per hour. If such site soils do not exist or if the design engineer demonstrates that it is not practical for engineering, environmental or safety reasons to site the stormwater infiltration BMP(s) in such soils, then the stormwater infiltration BMP(s) may be sited in soils verified by field testing to have permeability rates in excess of 20 inches per hour, provided that a bioretention system, designed, installed and maintained in accordance with the New Jersey BMP Manual, is installed to meet one of the following conditions:
The minimum design permeability rate for the soil within a BMP that relies on infiltration shall be 0.5 inch per hour. A factor of safety of two shall be applied to the soil's field-tested permeability rate to determine the soil's design permeability rate. (For example, if the field-tested permeability rate of the soil is four inches per hour, its design permeability rate would be two inches per hour). The minimum design permeability rate for the soil within a stormwater infiltration basin shall also be sufficient to achieve the minimum seventy-two-hour drain time described in Subsection B(1) above. The maximum design permeability shall be 10 inches per hour.
The predevelopment field test permeability rate shall be determined according to the methodologies provided in § 203-269C(3) of this article;
After all construction activities have been completed on the site and the finished grade has been established in the infiltration BMP, post-development field permeability tests shall also be conducted according to the methodologies provided in § 203-269C(3) of this article;
If the results of the post-development field permeability tests fail to achieve the minimum required design permeability rates in Subsection B(5) above utilizing a factor of safety of two, the stormwater infiltration BMP shall be renovated and retested until such minimum required design permeability rates are achieved; and
The design engineer shall conduct a mounding analysis, as defined in § 203-267, of all stormwater infiltration BMPs. The mounding analysis shall be conducted in accordance with the requirements in § 203-269C(3)(a). Where the mounding analysis identifies adverse impacts, the stormwater infiltration BMP shall be redesigned or relocated, as appropriate.
Unless the conditions in Subsection B(10)(a)[2] below are met, a stormwater infiltration basin shall not be placed into operation until its drainage area is completely stabilized. Instead, upstream runoff shall be diverted around the basin and into separate, temporary stormwater management facilities and sediment basins. Such temporary facilities and basins shall be installed and utilized for stormwater management and sediment control until stabilization is achieved in accordance with the Standards for Soil Erosion and Sediment Control in New Jersey, which is incorporated herein by reference as amended and supplemented.
If the design engineer determines that, for engineering, environmental or safety reasons, temporary stormwater management facilities and sediment basins cannot be constructed on the site, the stormwater infiltration basin may be placed into operation prior to the complete stabilization of its drainage area, provided that the basin's bottom during this period is constructed at a depth at least two feet higher than its final design elevation. All other infiltration BMP construction requirements in this section shall be followed. When the drainage area is completely stabilized, all accumulated sediment shall be removed from the infiltration BMP, which shall then be excavated to its final design elevation in accordance with the construction requirements of this section and the performance standards in § 203-264.
To avoid compaction of subgrade soils of BMPs that rely on infiltration, no heavy equipment such as backhoes, dump trucks or bulldozers shall be permitted to operate within the footprint of the BMP. All excavation required to construct a stormwater infiltration BMP shall be performed by equipment placed outside the BMP. If this is not possible, the soils within the excavated area shall be renovated and tilled after construction is completed to reverse the effects of compaction. In addition, post-development soil permeability testing shall be performed in accordance with Subsection B(5) of this section.
The overflow grate shall be secured to the outlet structure but be removable for emergencies and maintenance;
Safety ledges shall be constructed on the slopes of all new structural stormwater management measures having a permanent pool of water deeper than 2 1/2 feet. Such safety ledges shall be comprised of two steps. Each step shall be four feet to six feet in width. One step shall be located approximately 2 1/2 feet below the permanent water surface, and the second step shall be located one foot to 1 1/2 feet above the permanent water surface. See Subsection C(5)(a) below for an illustration of safety ledges in a stormwater management basin.
Stormwater collection system. This section is adapted from the Residential Site Improvements Standards, N.J.A.C. 5:21-7.2 through 7.3.
Where stormwater collection systems are required, they shall be adequately designed to accommodate all surface runoff coming to or accumulating on the tract. The determination of pipe and box culvert sizes shall be based on hydraulic computations using the Rational Method in which the actual watershed area tributary to the structure is measured. In setting the value of the runoff coefficient "C", consideration will be given to the physical features of the drainage basin. Due consideration should be given to the Hamilton Township Zoning Boundaries Map (on file in the Planning/Zoning Office) in estimating the future density of development of the drainage basin.
In computing runoff to size pipes and culverts, the rational formula shall be used:
the peak runoff rate in cubic feet per second
the runoff coefficient
the average rainfall intensity in inches per hour occurring at the time of concentration tc
the time of concentration in minutes
the size of the drainage area in acres
Typical C values for one-hundred-year frequency storm events appear in Table 1.
The Rational Method is most accurate when dealing with uniform drainage areas. Design engineers may divide nonuniform drainage areas into "uniform" subdrainage areas and calculate the runoff from each of these areas separately, or they may use the weighted average technique for a composite drainage area. Design engineers also may use runoff coefficients from the following sources, incorporated herein by reference:
HEC-22 - Urban Drainage Design Manual, Second Edition, FHWA-NHI-01-021, August 2001, U.S. Department of Transportation, Federal Highway Administration, as supplemented or amended to date.
New Jersey Department of Transportation (NJDOT) Roadway Design Manual, November 2001, as revised through March 28, 2003.
Design engineers may estimate time of concentration (tc) with Figure 1, Time of Concentration nomograph, from Roadway Design Manual, NJDOT, November 2001, as revised through March 28, 2003. Use of this figure is limited to the design of storm sewer systems. For other purposes, design engineers shall use the procedures outlined in Chapter 3 of Urban Hydrology for Small Watersheds, Technical Release No. 55 (TR-55), U.S. Department of Agriculture, NRCS.
The National Engineering Handbook, Part 630 (Hydrology) and Part 650 (Engineering Field Handbook) also may be used.
When using the Rational Method, rainfall intensity as a function of duration and storm frequency shall be based upon Figure 2, Rainfall Intensity Curves, and/or local rainfall frequency data, where available, for the two-, ten-, twenty-five-, and one-hundred-year storms. Design engineers shall use local rainfall frequency data. Current data may be obtained from the National Oceanic and Atmospheric Administration's (NOAA) National Weather Service, which is part of the U.S. Department of Commerce. See http://www.nws.noaa.gov/ohd/hdsc. In all instances, design engineers shall use a minimum time of concentration of 10 minutes. For storm sewer design, a ten-year to twenty-five-year storm frequency consistent with localized circumstances should be considered as a minimum, unless special circumstances are involved, such as inadequate downstream stormwater facilities, lack of positive overland relief, or evidence of local flooding. In such special circumstances, design engineers shall design facilities to accommodate, as a minimum, the following storm frequencies:
Ten-year storm for storm drain systems where excess flow, up to the one-hundred-year storm, can continue downgrade in the street and not exceed the gutter capacity. Also, ten-year storms shall be used at low points in storm drain systems with overland relief that is routed through the stormwater quantity control structure.
Twenty-five-year storm where flow in a storm drain is totally carried by pipe when conditions under Subsection D(4)(a) above do not apply, provided all overland relief up to the one-hundred-year storm is routed through the stormwater quantity control structure.
Twenty-five-year storm for culvert design where the culvert will be located in streams shown on the New Jersey State Atlas or the United States Coast and Geodetic Survey maps. Culverts with an upstream drainage area of 50 acres or more shall be designed to accommodate a one-hundred-year frequency storm in accordance with flood hazard area control regulations, N.J.A.C. 7:13-2.16.
Twenty-five-year storms for open channels where the upstream drainage area is less than 50 acres. When the upstream drainage area is 50 acres or more, design engineers shall design open channels to accommodate the one-hundred-year storm in accordance with flood hazard area control regulations, N.J.A.C. 7:13-2.16.
Computer software adaptations of the Rational Method or the NRCS's TR-55 are acceptable, provided their data and graphic printout allow review and evaluation.
Typical Runoff Coefficients (C Values) For 100-Year Frequency Storm
Good condition, grass cover on 75% or more of area
Fair condition, grass cover on 50% to 75% of area
Average Imperviousness
NOTE: NA denotes information is not available; design engineers should rely on another authoritative source.
SOURCE: Technical Manual for Land Use Regulation Program, Department of Environmental Protection, Bureaus of Inland and Coastal Regulations, Stream Encroachment Permits (Trenton, New Jersey, revised September 1995), p.12.
RAINFALL INTENSITY CURVES
Note: Adapted from Figure 2.1-2 in the NJDEP Technical Manual for Stream Encroachment Permits.
CLOSED CONDUITS
Vitrified sewer with manholes
Culvert straight and free of debris
Culvert with bends, connections
Sewer with manhole inlets
Unfinished steel form
Unfinished smooth wood form
Unfinished rough wood form
METAL, CORRUGATED
Finished with gravel on bottom
Gunite (good section)
Gunite (wavy section)
GRAVEL BOTTOM SIDES OF
STEEL, SMOOTH SURFACE
Planed, treated
Lined with roofing
EXCAVATED, DREDGED, OR NATURAL CHANNELS
CHANNELS NOT MAINTAINED AND BRUSH UNCUT
Dense weeds, high flow depth
DRAG LINE — EXCAVATED OR DREDGED
Light brush or banks
Short grass, few weeds
Dense weeds or aquatic plants
Cobble bottoms and clean sides
MINOR STREAMS (TOP WIDTH AT FLOOD STAGE LESS THAN 100 FEET)
(a) Streams on plain
Clean, straight, full stage, no rifts or deep pools
Same as above, but some stones and weeds
(b) Mountain streams, no vegetation in channel, banks usually steep, trees and bush along banks submerged at high stages
Design of runoff collection systems.
Design engineers shall determine hydraulic capacity for open-channel or closed-conduit flow based on the Manning equation or charts/nomographs based on this equation. The hydraulic capacity is termed Q and expressed as discharge in cubic feet per second as follows:
Q = (1.486/n)AR2/3 S1/2
Manning's roughness coefficient
Cross-sectional area of flow in square feet
Hydraulic radius in feet R = A/P where P is equal to the wetted perimeter measured in feet and defined as the length of a line of contact between the flowing water and the channel
Slope of energy grade line in feet per foot
The Mannings's roughness coefficients used by design engineers appear in Table 2.
A direct application of Manning's equation may be used for piped storm sewer systems. As an option, design engineers can use a standard step backwater calculation for storm sewer systems if the use of this approach is deemed appropriate by the designer. For other than pipe storm sewer systems, design engineers shall apply Manning's equation only when there is uniform flow, as defined by the following conditions:
The bottom slope of the channel, energy grade line, and water surface (hydraulic grade line) are parallel;
The flow regime is in the turbulent range of Reynolds number; and
The boundaries of the cross section of the channel do not move.
The design of open channels and conduits shall take tailwater effects into consideration.
Velocities in open channels, excluding water quality swales, at design flow shall not be less than 0.5 of a foot per second and not greater than a velocity that will begin to cause erosion or scouring of the channel. Design engineers shall determine permissible velocities for swales, open channels, and ditches using methods presented in Standards for Soil Erosion and Sediment Control in New Jersey at N.J.A.C. 2:90.
Velocities in closed conduits at design flow shall be at least two feet per second, but not more than the velocity that will cause erosion damage to the conduit, per the manufacturer's specifications. Minimum allowable pipe slopes shall produce velocity of at least three feet per second when the flow depth is full or half the pipe diameter.
Design engineers shall base culvert capacity on inlet/outlet analysis, as specified in Hydraulic Design of Highway Culverts, Hydraulic Design Senes (HDS) No. 5, Report No. FHWA-IP-85-15, U.S. Department of Transportation, Federal Highway Administration, September 1985, incorporated herein by reference.
Design engineers shall determine pipe size based on design runoff, conduit entrance conditions, and hydraulic capacity.
In general, no pipe size in the storm drainage system shall be less than 15 inches in diameter. Design engineers may use a twelve-inch-diameter pipe as a cross-drain to a single inlet, if the run does not exceed 50 feet.
Where pipe sizes are increased, the invert of the larger pipe shall be dropped so that the tops of the pipes will be at the same elevation.
All discharge pipes shall terminate with an appropriate precast concrete or flared-end section or concrete headwall with or without wingwalls, as conditions require. Design engineers shall consider such site conditions as slope, soil stability, vegetation, grade, and size of conduit to determine whether or not to use wingwalls.
Materials used in the construction of storm sewers shall be constructed of reinforced concrete, ductile iron, or corrugated polyethylene or, when approved by the municipal engineer, corrugated metal. The most cost-effective materials shall be permitted that conform to local site conditions and reflect the relevant operations, maintenance, and system character of the municipal stormwater system. Unless otherwise specified by the Township Engineer, reinforced concrete pipe shall be used in all construction within the public right-of-way. Specifications referred to, such as ASTM or AWWA, shall be the latest revision in effect at the time of application.
The following apply to reinforced concrete pipe:
Circular reinforced concrete pipe and fittings shall meet the requirements of ASTM C76.
Elliptical reinforced concrete pipe shall meet the requirements of ASTM C507.
Joint design and joint material for circular pipe shall conform to ASTM C443.
Joints for elliptical pipe shall be bell and spigot or tongue and grove sealed with butyl, rubber tape, rubber ring gaskets, or external sealing bands conforming to ASTM C877.
All pipe shall be Class III minimum unless loading conditions call for stronger pipe (i.e., higher class).
The minimum depth of cover over the concrete pipe shall be as designated by the American Concrete Pipe Association in Table 3.
Minimum depth of cover standards for ductile iron and corrugated polyethylene pipe shall conform to manufacturer standards.
Ductile iron pipe shall conform to ANSI/AWWA C151/A21.51. Joints shall conform to ANSI/AWWA C111/A21.ii or ANSI/AWWA C115/A21.15, as appropriate. Pipe shall be designed in accordance with ANSI/AWWA C150/A21.50. The outside of the pipe shall be coated in accordance with ANSI/AWWA C151/A21.51 and the inside lined in accordance with ANSI/AWWA C104/A21 4. Ductile iron pipe shall be installed in accordance with AWWA C600.
Minimum Depth Of Coverage Over Concrete Pipe
(surface to top of pipe in inches)
Minimum cover as designated by the American Concrete Pipe Association.
Corrugated polyethylene pipe shall conform to AASHTO M252 for three inches through 10 inches and AASHTO M294 for sizes 12 inches and larger. All pipes greater than 12 inches in diameter shall be Type S, unless conditions dictate otherwise. Materials shall conform to ASTM D3350, Standard Specification for Polyethylene Plastics Pipe and Fittings Materials. Pipe joints and fittings shall be compatible with the pipe material and shall conform to the same standards and specifications as the pipe material. Pipe couplers shall not cover less than one full corrugation on each section of pipe. Installation shall be in accordance with ASTM D2321 Standard Practice for Underground Installation of Thermoplastic Pipe for Sewers and Other Gravity-Flow Applications. Backfill material shall be placed in six-inch lifts and compacted to 95% maximum dry density, per AASHTO T99. In areas of high groundwater tables, design engineers shall check for flotation.
Where used, corrugated aluminum pipe arch shall conform to the requirements of American Association of State Highway Officials Designation M-196-62 or American Association of State Highway Officials Designation M-211-65, both as amended. The aluminum alloy sheets shall conform to the requirements of the American Society for Testing and Materials B209 Alloy AA1 clad 3004-H34, as amended. Aluminum pipe shall not be used in dedicated Township streets, and the supplier shall give written certification that soil conditions will not adversely affect the pipe.
Where used, cast-iron pipe, together with mechanical joints, shall conform to the American Standards Association Specifications therefor, and unless otherwise specified by the Township Engineer, cast-iron pipe shall be Class 22 for pipe diameters of 12 inches or less and thickness Class 21 for a pipe diameter of 14 inches or more.
Pipe bedding and backfill shall be provided as specified in Design and Construction of Urban Stormwater Management Systems, ASCE Manuals and Reports of Engineering Practice No. 77, 1993, incorporated herein by reference. Bedding and backfill for any pipe material not covered by this manual shall be installed in accordance with manufacturer's recommendations. The municipal engineer may require the developer to provide professional certification as to the suitability of backfill material and where such suitability does not exist, any modifications needed to use on-site material and the appropriate methods to install this material. The municipal and/or utility engineer shall rely on this certification.
No pipe shall be placed on private property unless the owner of the land is to own or operate the pipe, or an easement deeded to the municipality is obtained. All easements shall be a minimum of 20 feet wide unless depth of pipe, soil conditions, or additional utilities require wider. Where the easement is located adjacent to a right-of-way, the municipality may approve a narrower easement.
All drainage pipes shall be laid in straight lines between drainage structures except when otherwise specifically provided. When deviation from a straight line is permitted, the deflection of each joint shall not exceed the manufacturer's recommended maximum for the pipe, joint and size of pipe being installed. All pipe shall conform to specified lines, grades and dimensions. Manufacturer's recommendations and specifications for bedding, backfill placement and compaction and installation procedures shall be strictly adhered to and followed.
No defective or leaking pipes, joints, connections, manholes, inlets or other parts of the work will be acceptable. All visible leakage of any description, no matter where located, shall be corrected by the contractor in a manner satisfactory to the Township Engineer.
Underdrains with a minimum pipe size of six inches must be constructed where groundwater interferes with the stability of the road base or with pavement construction.
Subsurface structure excavations shall be carried out by the contractor and, only where considered necessary by the Township Engineer, shall be carried below the required facility installation level to remove and replace unstable soils with thoroughly tamped gravel, crushed stone or crushed slag. Adequate bracing, shoring and sheeting shall be installed to protect workmen, members of the public, public and private property and the work underway. Where deemed necessary by the Township Engineer, the contractor shall provide, install and operate an adequate well-point system for dewatering to stabilize excavation bottoms and banks.
Inlets, catch basins, manholes, and outlets. This subsection is adapted from the Residential Site Improvement Standards, N.J.A.C. 5:21 - 7.4.
Design engineers shall design inlets, catch basins, and manholes in accordance with the NJDOT Standard Specifications for Road and Bridge Construction, November 2001, as supplemented. For Type A inlets, they should use a frame and single grate. Type B inlets require a frame, grate, and curb-type inlet with back piece. Type E inlets require a frame and double grate.
Design engineers shall use one of the following grate types for stormwater inlets:
The NJDOT bicycle-safe grate, as described in the NJDOT Bicycle Compatible Roadways and Bikeways Planning Design Guidelines (April 1996).
If there is no bicycle traffic, a grate where each individual clear space in that grate has an area of no more than seven square inches or is no greater than 0.5 inch across the smallest dimension.
Another grate design may be used, provided that:
There will be no bicycle traffic; and
Runoff discharging through the inlet is routed through a trash rack that complies with N.J.A.C. 5:21-7.8(d)1.ii.
Whenever a curb-opening inlet is used, the clear space in that curb opening (or each individual clear space if the curb opening has two or more clear spaces) shall have an area of no more than seven square inches, or be no greater than two inches across the smallest dimension.
Exception: Compliance with the above dimensional requirements for curb openings shall not be required, provided that runoff discharging through the inlet is routed through a trash rack that complies with N.J.A.C. 5:21-7.8(d)1.ii.
Inlet spacing depends on the inlet capacity. Maximum gutter line flow is 400 feet. The maximum capacity of a curb inlet shall be six cubic feet per second. Area inlets in parking lots should be limited to three cubic feet per second.
Manholes shall be precast concrete or concrete block coated with two coats of portland cement mortar outside the manhole. Masonry brick may be used to make vertical adjustments to rims, as long as the adjustments are 12 inches or less. In acidic soils, all manholes shall have two coats of black bitumastic waterproofing applied per manufacturer's instruction.
If precast manhole barrels and cones are used, they shall conform to ASTM Specification C478, with round rubber gasketed joints conforming to ASTM Specification C923. Both ASTM specifications are incorporated herein by reference. Maximum absorption shall be 8% in accordance with ASTM Specification C478, Method A.
If precast manholes are used, the top riser section shall terminate less than one foot below the finished grade and the manhole cover shall be flush with the finished grade.
Manhole frames and covers shall be of cast iron, conforming to ASTM Specification A48, Class 30, incorporated herein by reference, and be suitable for H-20 loading capacity. Manhole covers in remote locations may have a locking device.
The channel should be, insofar as possible, a smooth continuation of the pipe. The pipe may be laid through the manhole and the top half removed by saw cut. The completed channel should be U-shaped. The channel height shall be three-fourths of the diameter of the pipe.
The bench should provide good footing for a workman, and a place where minor tools and equipment can be laid. It must have a slope of 4% to 8%.
Applicability. Projects subject to review pursuant to § 203-261C of this article shall comply with the requirements of Subsections B and C below.
The design engineer shall prepare an inspection, maintenance and repair plan for the stormwater management measures, including both structural and nonstructural measures incorporated into the design of a major development. This plan shall be submitted as part of the checklist requirements established in § 203-262C. Inspection and maintenance guidelines for stormwater management measures are available in the New Jersey BMP Manual. At the time of approval of a site plan or subdivision containing a structural stormwater management measure, the applicant shall file a declaration of covenants and restrictions for drainage structures with the Planning Board and shall record the same with the clerk of the County of Atlantic. A standard form of this declaration is on file with the Hamilton Township Planning Board.
The name, address and telephone number of the person or persons responsible for regular inspections and preventative and corrective maintenance (including repair and replacement). If the responsible person or persons is a corporation, company, partnership, firm, association, municipality or political subdivision of this state, the name and telephone number of an appropriate contact person shall also be included. All inspections, maintenance and repairs are to be performed under the direction of a professional engineer licensed in the State of New Jersey.
The person responsible for inspection, maintenance and repair identified under Subsection B(2) above shall submit the updated inspection, maintenance and repair plan and the documentation required by Subsection B(2) and (3) above to the Township of Hamilton once per year.
The person responsible for inspection, maintenance and repair identified under Subsection B(2) above shall retain and make available, upon request by any public entity with administrative, health, environmental or safety authority over the site, the inspection, maintenance and repair plan and the documentation required by Subsection B(2) and (3) above.
In the event that the stormwater management measure becomes a public health nuisance or danger to public safety or public health, or if it is in need of maintenance or repair, the Township of Hamilton shall so notify the responsible person in writing. Upon receipt of that notice, the responsible person shall have 14 days to effect maintenance and repair of the facility in a manner that is approved by the municipal engineer or the municipal engineer's designee. The Township of Hamilton, at its discretion, may extend the time allowed for effecting maintenance and repair for good cause. If the responsible person fails or refuses to perform such maintenance and repair within the allowable time, the Township of Hamilton may immediately proceed to do so with its own forces and equipment and/or through contractors. The costs and expenses of such maintenance and repair by the Township of Hamilton shall be entered on the tax roll as a special charge against the property and collected with any other taxes levied thereon for the year in which the maintenance and repair was performed.
After every storm exceeding one inch of rainfall: inspect and, if necessary, remove and replace K5 sand layer and accumulated sediment, to restore original infiltration rate.
The assumption of the inspection and maintenance program by a municipality, county, public utility or homeowners' association; or
The posting of a financial surety in an amount equivalent to the cost of both ongoing maintenance activities and necessary structural replacements; or
The propagation, rearing and subsequent harvesting of aquatic organisms in controlled or selected environments, and their subsequent processing, packaging and marketing, including, but not limited to, activities to intervene in the rearing process to increase production such as stocking, feeding, transplanting and providing for protection from predators.
The use of vegetation (usually grasses or wetland plants) to filter and treat stormwater runoff as it is conveyed through an open channel or swale.
The maximum water depth during treatment of the stormwater quality design storm shall be 12 inches in a bioretention basin.
Sometimes called "vegetated swales" or "bioswales." Open, shallow, vegetated channel that slows runoff, filters it and promotes infiltration into the ground. To function properly, swales must be carefully designed and maintained. The vegetation in swales helps to trap pollutants and reduces the velocity of stormwater runoff, which allows it to percolate into the ground. Vegetated swales can be used along driveways, interior roadways, within parking lots and within street side street tree planting areas. The maximum water depth during treatment of the stormwater quality design storm shall be 18 inches in a bioretention swale.
A bioretention system consists of a soil bed planted with native vegetation located above an underdrained sand layer. It can be configured as either a bioretention basin or a bioretention swale. Stormwater runoff entering the bioretention system is filtered first through the vegetation and then the sand/soil mixture before being conveyed downstream by the underdrain system. The bottom of a bioretention system, including any underdrain piping or gravel layer, must be a minimum of one foot above the seasonal high groundwater table. The planting soil bed and underdrain system shall be designed to fully drain the stormwater quality design storm runoff volume within 72 hours. Runoff storage depths above the planting bed surface are typically shallow. The adopted TSS removal rate for bioretention systems is 90%. Pursuant to § 203-265B(4)(b) of the Township's Land Use Ordinance, bioretention systems may be constructed without an underdrain system and may discharge directly to underlying soils where such systems are used to address insitu soils with permeability rates in excess of 20 inches per hour. As defined below, rain gardens are a type of bioretention system.
A designated transitional area around a stream, lake or wetland left in a natural, usually vegetated state so as to protect the water body from runoff pollution. Development is often restricted or prohibited in a buffer zone.
Either a written statement signed and sealed by a licensed New Jersey professional engineer attesting that a BMP design or stormwater management system conforms to or meets a particular set of standards or to action taken by the Commission pursuant to N.J.A.C. 7:50-3, Part II or Part IV. Depending upon the context in which the term is used, the terms "certify" and "certified" shall be construed accordingly.
In the case of development on agricultural land, i.e., lands used for an agricultural use or purpose as defined at N.J.A.C. 7:50-2.11, development means any activity that requires a state permit; any activity reviewed by the County Agricultural Boards (CAB) and the State Agricultural Development Committee (SADC), and municipal review of any activity not exempted by the Right to Farm Act, N.J.S.A. 4:1C-1 et seq.
Any division of land into five or more lots; any construction or expansion of any housing development of five or more dwelling units; any construction or expansion of any commercial or industrial use or structure on a site of more than three acres; or any development, grading, clearing or disturbance of an area in excess of 5,000 square feet. Disturbance for the purpose of this article is the placement of impervious surface or exposure and/or movement of soil or bedrock or clearing, cutting or removing of vegetation.
An area or feature which is of significant environmental value, including, but not limited to: stream corridors; natural heritage priority sites; habitat of endangered or threatened animal species; threatened or endangered plants of the Pinelands pursuant to N.J.A.C. 7:5-6.27(a); large areas of contiguous open space or upland forest; steep slopes; and wellhead protection and groundwater recharge areas. T&E habitat constitutes habitat that is critical for the survival of a local population of threatened and endangered species or habitat that is identified using the Department's Landscape Project as approved by the Department's Endangered and Nongame Species Program, whichever is more inclusive. Threatened and endangered wildlife shall be protected in conformance with N.J.A.C. 7:50-6.33.
The approval by the approving authority of a variance or other material departure from strict compliance with any section, part, phrase or provision of this article. An exception may be granted only under certain specific, narrowly defined conditions described herein, and for development within the Pinelands Area, does not constitute a waiver of strict compliance with any section, part, phrase or provision of the Pinelands Comprehensive Management Plan (N.J.A.C. 7:50-1.1 et seq.).
An area in an industrial or commercial development site: where solvents and/or petroleum products are loaded/unloaded, stored, or applied; where pesticides are loaded/unloaded or stored; where hazardous materials are expected to be present in greater than "reportable quantities" as defined by the United States Environmental Protection Agency (EPA) at 40 CFR 302.4; where recharge would be inconsistent with an NJDEP-approved remedial action work plan or landfill closure plan; and/or where a high risk exists for spills of toxic materials, such as gas stations and vehicle maintenance facilities. The term "HPLA" shall have the same meaning as "high pollutant loading area."
A monetary fee collected by the Township of Hamilton in lieu of requiring strict on-site compliance with the groundwater recharge, stormwater runoff quantity and/or stormwater runoff quality standards established in this article.
Acts necessary to prevent, limit, remedy or compensate for conditions that may result from those cases where an applicant has demonstrated the inability or impracticality of strict compliance with the stormwater management requirements set forth in N.J.A.C. 7:8, in an adopted regional stormwater management plan, or in a local ordinance which is as protective as N.J.A.C. 7:8, and an exception from strict compliance is granted by the Township of Hamilton and the Pinelands Commission, if applicable.
Guidance developed by the New Jersey Department of Environmental Protection, in coordination with the New Jersey Department of Agriculture, the New Jersey Department of Community Affairs, the New Jersey Department of Transportation, municipal engineers, county engineers, consulting firms, contractors, and environmental organizations to address the standards in the New Jersey Stormwater Management Rules, N.J.A.C. 7:8. The BMP Manual provides examples of ways to meet the standards contained in the rule. An applicant may demonstrate that other proposed management practices will also achieve the standards established in the rules. The Manual, and notices regarding future versions of the Manual, are available from the Division of Watershed Management, NJDEP, PO Box 418, Trenton, New Jersey 08625; and on the NJDEP's website, www.njstormwater.org. The term "New Jersey BMP Manual" shall have the same meaning as "New Jersey Stormwater Best Management Practices Manual."
The New Jersey Pollutant Discharge Elimination System as set forth in N.J.S.A. 58:10A-1 et seq. and in N.J.A.C. 7:14A.
Any human-made or human-induced activity, factor, or condition, other than a point source, that may temporarily or permanently change any chemical, physical, biological, or radiological characteristic of waters of the state from what was or is the natural, pristine condition of such waters, or that may increase the degree of such change; or
The rate at which water moves through a saturated unit area of soil or rock material at hydraulic gradient of one, determined as prescribed in N.J.A.C. 7:9A-6.2 (tube permeameter test), N.J.A.C. 6.5 (pit bailing test) or N.J.A.C. 6.6 (piezometer test). Alternative permeability test procedures may be accepted by the approving authority, provided the test procedure attains saturation of surrounding soils, accounts for hydraulic head effects on infiltration rates, provides a permeability rate with units expressed in inches per hour and is accompanied by a published source reference. Examples of suitable sources include hydrogeology, geotechnical, or engineering text and design manuals, proceedings of American Society for Testing and Materials (ASTM) symposia, or peer review journals. Neither a soil permeability class rating test, as described in N.J.A.C. 7:9A-6.3, nor a percolation test, as described in N.J.A.C. 7:9A-6.4, is an acceptable test for establishing permeability values for the purpose of complying with this article.
A BMP overlaid with appropriate mulch and suitable vegetation and designed, constructed and maintained for the purpose of providing infiltration or recharge of stormwater into the soil and/or underground aquifer.
A particle size category consisting of mineral particles which are between 0.05 millimeter and 2.0 millimeters in equivalent spherical diameter. Also, a soil textural class having 85% or more of sand and a content of silt and clay such that the percentage of silt plus 1.5 times the percentage of clay does not exceed 15, as shown in § 203-269C(1) (USDA Soil Textural Triangle).
Unsaturated soil, above the seasonally high water table, which contains less than 50% by volume of coarse fragments and which has a tested permeability rate of between one inch and 20 inches per hour.
The Planning Board, Zoning Board of Adjustment or other board, agency or official of the Township of Hamilton with authority to approve or disapprove subdivisions, site plans, construction permits, building permits or other applications for development approval. For the purposes of reviewing development applications and ensuring compliance with the requirements of this article, the Township of Hamilton may designate the municipal engineer or other qualified designee to act on behalf of the Township of Hamilton.
The ocean and its estuaries, all springs, streams and bodies of surface and groundwater, whether natural or artificial, within the boundaries of New Jersey or subject to its jurisdiction.
Those lands which are inundated or saturated by water at a magnitude, duration and frequency sufficient to support the growth of hydrophytes. Wetlands include lands with poorly drained or very poorly drained soils as designated by the National Cooperative Soils Survey of the Soil Conservation Service of the United States Department of Agriculture. Wetlands include coastal wetlands and inland wetlands, including submerged lands. The New Jersey Pinelands Commission Manual for Identifying and Delineating Pinelands Area Wetlands: A Pinelands Supplement to the Federal Manual for Identifying and Delineating Jurisdictional Wetlands, dated January, 1991, as amended, may be utilized in delineating the extent of wetlands based on the definitions of wetlands and wetlands soils contained in this section, N.J.A.C. 7:50 2.11, 6.4 and 6.5. The term "wetland" shall have the same meaning as "wetlands."
Any person who erects, constructs, alters, repairs, converts, maintains, or uses any building, structure or land in violation of this article shall be subject to the penalties referenced in § 203-218, entitled Violations and penalties.
The New Jersey Geological Survey Report GSR-32: A Method for Evaluating Groundwater Recharge Areas in New Jersey. Available at http://www.njgeology.org/geodata/dgs99-2.htm.
NJDEP nonstructural strategies point system. The New Jersey Stormwater Management Rules at N.J.A.C. 7:8-5.2(a), and § 203-264A of this article, require nonstructural stormwater management strategies to be incorporated into the site design of a major development. A total of nine strategies are to be used to the maximum extent practical to meet the groundwater recharge, stormwater quality and stormwater quantity requirements of the rules prior to utilizing structural stormwater management measures. The New Jersey nonstructural stormwater management strategies point system (NSPS) provides a tool to assist planners, designers and regulators in determining that the strategies have been used to the "maximum extent practical" at a major development as required by the rules. Refer online to http://www.njstormwater.org for information on the NSPS.
A zone of saturation which exists immediately below a hydraulically restrictive horizon, and which has an upper surface that is at a pressure greater than atmospheric, either seasonally or throughout the year.
A particle size category consisting of mineral particles which are smaller than 0.002 millimeter in equivalent spherical diameter. Also, a soil textural class having more than 40% clay, less than 45% sand, and less than 40% silt, as shown in Subsection C(1) (USDA Soil Textural Triangle).
A soil textural class having 27% to 40% clay and 20% to 45% sand, as shown in Subsection C(1) (USDA Soil Textural Triangle).
A report prepared by the U.S. Department of Agriculture, Natural Resources Conservation Service, which includes maps showing the distribution of soil mapping units throughout a particular county together with narrative descriptions of the soil series shown and other information relating to the uses and properties of the various soil series.
EQUIVALENT SPHERICAL DIAMETER OF A PARTICLE
The diameter of a sphere which has a volume equal to the volume of the particle.
A soil textural class, as shown in Subsection C(1) (USDA Soil Textural Triangle), that has a maximum of 85% to 90% sand with a percentage of silt plus 1.5 times the percentage of clay not in excess of 15; or a minimum of 70% to 85% sand with a percentage of silt plus 1.5 times the percentage of clay not in excess of 30.
The moisture content corresponding to the transition between the plastic and semi-solid states of soil consistency. This corresponds to the lowest soil moisture content at which the soil can be molded in the fingers to form a rod or wire, 1/8 inch in thickness, without crumbling.
Characterized by a soil aggregate which has one axis distinctly shorter than the other two and is oriented with the short axis vertical.
A soil textural class having 35% or more of clay and 45% or more of sand, as shown in Subsection C(1) (USDA Soil Textural Triangle).
A soil textural class, as shown in Subsection C(1) (USDA Soil Textural Triangle), that has a maximum of 20% clay, and the percentage of silt plus twice the percentage of clay exceeds 30, and contains 52% or more sand; or less than 7% clay, less than 50% silt, and between 43% and 52% sand.
A particle size category consisting of mineral particles which are between 0.002 and 0.05 millimeter in equivalent spherical diameter. It also means a soil textural class having 80% or more of silt and 12% or less of clay, as shown in Subsection C(1) (USDA Soil Textural Triangle).
A soil textural class having 50% or more of silt and 12% to 27% of clay; or 50% to 80% of silt and less than 12% of clay, as shown in Subsection C(1) (USDA Soil Textural Triangle).
A soil textural class having 40% or more of clay and 40% or more of silt, as shown in Subsection C(1) (USDA Soil Textural Triangle).
A soil textural class having 27% to 40% of clay and less than 20% of sand, as shown in Subsection C(1) (USDA Soil Textural Triangle).
One of the classes of soil texture defined within the USDA system of classification (Soil Survey Manual, Agricultural Handbook No. 18, USDA Soil Conservation Service 1962).
The depth below the ground surface or the elevation with respect to some reference level, of the water level observed within a soil profile pit or boring, or within a piezometer, after this level has stabilized or become relatively constant with the passage of time.
The system of classifying soil texture used by the United States Department of Agriculture which defines 12 soil textural classes based upon the weight percentages of sand, silt and clay in that portion of the soil which passes through a sieve with two-millimeter openings. The soil textural classes are shown graphically on the USDA Soil Textural Triangle, as shown in Subsection C(1).
All soil test pits and soil permeability results shall be performed under the direct supervision of a professional engineer. All soil logs and permeability test data shall be accompanied by a certification by a professional engineer. The results and location (horizontal and vertical) of all soil test pits and soil permeability tests, both passing and failing, shall be reported to the Township of Hamilton.
Each soil test pit log shall report the depth to seasonally high water level, either perched or regional, and the static water level based upon the presence of soil mottles or other redoximorphic features, and observed seepage or saturation. Where redoxomorphic features including soil mottles resulting from soil saturation are present, they shall be interpreted to represent the depth to the seasonal high water table unless soil saturation or seepage is observed at a higher level. When the determination of the seasonally high water table shall be made in ground previously disturbed by excavation, direct observation of the static water table during the months of January through April shall be the only method permitted.
Stormwater infiltration BMPs shall not be installed in soils that exhibit artesian groundwater conditions. A permeability test shall be conducted in all soils that immediately underlie a perched zone of saturation. Any zone of saturation which is present below a soil horizon which exhibits an in-place permeability of less than 0.2 inch per hour shall be considered an artesian zone of saturation unless a minimum one-foot-thick zone of unsaturated soil, free of mottling or other redoximorphic features and possessing a chroma of four or higher, exists immediately below the unsuitable soil.
A minimum of one permeability test shall be performed at each soil test pit location. The soil permeability rate shall be determined using test methodology as prescribed in N.J.A.C. 7:9A-6.2 (tube permeameter test), 6.5 (pit bailing test) or 6.6 (piezometer test). When the tube permeameter test is used, a minimum of two replicate samples shall be taken and tested. Alternative permeability test procedures may be accepted by the approving authority, provided the test procedure attains saturation of surrounding soils, accounts for hydraulic head effects on infiltration rates, provides a permeability rate with units expressed in inches per hour and is accompanied by a published source reference. Examples of suitable sources include hydrogeology, geotechnical or engineering text and design manuals, proceedings of American Society for Testing and Materials (ASTM) symposia, or peer-review journals. Neither a soil permeability class rating test, as described in N.J.A.C. 7:9A-6.3, nor a percolation test, as described in N.J.A.C. 7:9A-6.4, is an acceptable test for establishing permeability values for the purpose of complying with this article.
Soil permeability tests shall be conducted on the most hydraulically restrictive horizon or substratum to be left in place below the basin as follows. Where no soil replacement is proposed, the permeability tests shall be conducted on the most hydraulically restrictive horizon or substratum within four feet of the lowest elevation of the basin bottom or to a depth equal to two times the maximum potential water depth within the basin, whichever is greater. Where soil replacement is proposed, the permeability tests shall be conducted within the soil immediately below the depth of proposed soil replacement or within the most hydraulically restrictive horizon or substratum to a depth equal to two times the maximum potential water depth within the basin, whichever is greater. Permeability tests may be performed on the most hydraulically restrictive soil horizons or substrata at depths greater than those identified above based upon the discretion of the design or testing engineer. The tested infiltration rate should then be divided by two to establish the soil's design permeability rate. Such division will provide a 100% safety factor to the tested rate.
The minimum acceptable "tested permeability rate" of any soil horizon or substratum shall be one inch per hour. Soil materials that exhibit tested permeability rates slower than one inch per hour shall be considered unsuitable for stormwater infiltration. The maximum reportable "tested permeability rate" of any soil horizon or substratum shall be no greater than 20 inches per hour regardless of the rate attained in the test procedure.
A groundwater mounding analysis shall be provided for each stormwater infiltration BMP. The groundwater mounding analysis shall calculate the maximum height of the groundwater mound based upon the volume of the maximum design storm. The professional engineer conducting the analysis shall provide the municipal engineer with the methodology and supporting documentation for the mounding analysis used and shall certify to the Township of Hamilton, based upon the analysis, that the groundwater mound will not cause stormwater or groundwater to breakout to the land surface or cause adverse impact to adjacent surface water bodies, wetlands or subsurface structures, including but not limited to basements and septic systems. If there is more than one infiltration BMP proposed, the model shall indicate if and how the mounds will interact. The mounding analysis shall be calculated using the most restrictive soil horizon that will remain in place within the explored aquifer thickness unless alternative analyses are authorized by the municipal engineer. The mounding analysis shall be accompanied by a cross section of the infiltration BMP and surrounding topography and the mound analysis shall extend out to the point(s) at which the mound intersects with the preexisting maximum water table elevation.
The applicant shall demonstrate that stormwater infiltration BMPs meet the seventy-two-hour drain time requirement established in § 203-265B(1) of this article.
Where flows from the water quality design storm as specified in § 203-263 are conveyed through any device (e.g., end-of-pipe netting facility, manufactured treatment device, or a catch basin hood) that is designed, at a minimum, to prevent delivery of all solid and floatable materials that could not pass through one of the following:
Where flows are conveyed through a trash rack that has parallel bars with one-inch spacing between the bars, to the elevation of the water quality design storm as specified in § 203-263 of this article; or
Where the NJDEP determines, pursuant to the New Jersey Register of Historic Places Rules at N.J.A.C. 7:4-7.2(c), that action to meet this standard is an undertaking that constitutes an encroachment or will damage or destroy the New Jersey Register listed historic property.
Catch basins. Catch basins are storm drain inlets with or without sumps. Catch basins may provide pretreatment for other stormwater BMPs by capturing large sediments. The sediment and pollutant removal efficiency of catch basins depends on the size of the sump and the performance of routine maintenance to retain the available sediment storage space in the sump. Where catch basins with sumps are proposed, the minimum two feet of separation between the bottom of the sump and seasonally high water table shall be provided.
New Jersey BMP Manual. Available from the Division of Watershed Management, New Jersey Department of Environmental Protection, P.O. Box 418, Trenton, New Jersey 08625; or online at http://www.njstormwater.org.
NJDEP Stormwater Management Facilities Maintenance Manual. Available from the Division of Watershed Management, New Jersey Department of Environmental Protection, P.O. Box 418, Trenton, New Jersey 08625; or online at http://njedl.rutgers.edu/ftp/PDFs/1188.pdf.
State Soil Conservation Committee Standards for Soil Erosion and Sediment Control in New Jersey. Available from all State Soil Conservation Districts, including Cape Atlantic Conservation District, 6260 Old Harding Highway, Mays Landing, New Jersey 08330. Phone: 609-624-3144; fax 609-625-7360; Website: www.capeatlantic.org.
Cape Atlantic Conservation District, 6260 Old Harding Highway, Mays Landing, New Jersey 08330. Phone: 609-625-3144; Fax 609-625-7360; Web site: www.capeatlantic.org.
§ 203-271 Stormwater Landscape Illustrations, Appendix A; Appendix B. [1]
Editor's Note: Appendixes A and B are included at the end of this chapter.