A. Stormwater management measures for development regulated under this article shall be designed to provide erosion control, groundwater recharge, stormwater runoff quantity control and stormwater runoff quality treatment in accordance with this article.
(1) Major development shall meet the minimum design and performance standards for erosion control established under the Soil Erosion and Sediment Control Act, N.J.S.A. 4:24-39 et seq., and implementing rules at N.J.A.C. 2:90 and 16:25A.
(2) All development regulated under this article shall meet the minimum design and performance standards for groundwater recharge, stormwater runoff quality, and stormwater runoff quantity at § 175-172O., P., and Q. by incorporating green infrastructure as provided at § 175-172N.
B. All development regulated under this article shall incorporate a maintenance plan for the stormwater management measures in accordance with § 175-178.
C. Stormwater management measures shall avoid adverse impacts of concentrated flow on habitat for threatened and endangered species in accordance with N.J.A.C. 7:8-5.2(c) and N.J.A.C. 7:50-6.27 and 6.33.
D. Tables 1, 2, and 3 below summarize the ability of stormwater best management practices identified and described in the New Jersey Stormwater BMP Manual to satisfy the green infrastructure, groundwater recharge, stormwater runoff quality and stormwater runoff quantity standards specified in § 175-172N., O., P., and Q. When designed in accordance with the most current version of the New Jersey Stormwater BMP Manual and this article, the stormwater management measures found in Tables 1, 2, and 3 are presumed to be capable of providing stormwater controls for the design and performance standards as outlined in the tables below. Upon amendments of the New Jersey Stormwater BMP Manual to reflect additions or deletions of BMPs meeting these standards, or changes in the presumed performance of BMPs designed in accordance with the New Jersey Stormwater BMP Manual, the NJDEP shall publish in the New Jersey Registers a notice of administrative change revising the applicable table. The most current version of the BMP Manual can be found on the NJDEP website at: https://njstormwater.org/bmp_manual2.htm.
E. Where the BMP tables at N.J.A.C. 7:8-5.2(f) differ with Tables 1, 2 and 3 below due to amendment, the BMP Tables at N.J.A.C. 7:8-5.2(f) shall take precedence, except that in all cases the lowest point of infiltration must maintain a minimum separation of two (2) feet to seasonal high water table as required by § 175-172H.(2) unless otherwise noted.
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Table 1: Green Infrastructure BMPs for Groundwater Recharge, Stormwater Runoff
Quality, and/or Stormwater Runoff Quantity
Best Management Practice | Stormwater Runoff Quality TSS Removal Rate (percent) | Stormwater Runoff Quantity | Groundwater Recharge | Minimum Separation from Seasonal High Water Table (Feet) |
Cistern | 0 | Yes | No | -- |
Dry Well(a) | 0 | No | Yes | 2 |
Grass Swale | 50 or less | No | No | 2(e) |
1(f) | ||||
Green Roof | 0 | Yes | No | -- |
Manufactured Treatment Device(a), (g) | 50 or 80 | No | No | Dependent upon the device |
Pervious Paving System(a) | 80 | Yes | Yes(b) | 2(b) |
No(c) | 2(c) | |||
Small-Scale Bioretention Basin(a) | 80 or 90 | Yes | Yes(b) | 2(b) |
No(c) | 1(c) | |||
Small-Scale Infiltration Basin(a) | 80 | Yes | Yes | 2 |
Small Scale Sand Filter(a) | 80 | Yes | Yes | 2 |
Vegetative Filter Strip | 60-80 | No | No | -- |
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Table 2: Green Infrastructure BMPs for Stormwater Runoff Quantity
(or for Groundwater Recharge and/or Stormwater Runoff Quality with a
Variance from N.J.A.C. 7:8-5.3)
Best Management Practice | Stormwater Runoff Quality TSS Removal Rate (percent) | Stormwater Runoff Quantity | Groundwater Recharge | Minimum Separation from Seasonal High Water Table (Feet) |
Bioretention System | 80 or 90 | Yes | Yes(b) | 2(b) |
No(c) | 1(c) | |||
Infiltration Basin | 80 | Yes | Yes | 2 |
Sand Filter(b) | 80 | Yes | Yes | 2 |
Standard Constructed Wetland | 90 | Yes | No | 2(i) |
Wet Pond(d) | 50-90 | Yes | No | 2(i) |
Table 3: BMPs for Groundwater Recharge, Stormwater Runoff Quality, and/or
Stormwater Runoff Quantity only with a Variance from N.J.A.C. 7:8-5.3
Best Management Practice | Stormwater Runoff Quality TSS Removal Rate (percent) | Stormwater Runoff Quantity | Groundwater Recharge | Minimum Separation from Seasonal High Water Table (Feet) |
Blue Roof | 0 | Yes | No | N/A |
Extended Detention Basin | 40-60 | Yes | No | 2 |
Manufactured Treatment Device(h) | 50 or 80 | No | No | Dependent upon the device |
Sand Filter(c) | 80 | Yes | No | 2 |
Subsurface Gravel Wetland | 90 | No | No | 2 |
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Best Management Practice | Stormwater Runoff Quality TSS Removal Rate (percent) | Stormwater Runoff Quantity | Groundwater Recharge | Minimum Separation from Seasonal High Water Table (Feet) |
Wet Pond | 50-90 | Yes | No | 2(i) |
Footnotes to Tables 1, 2, and 3: (a) Subject to the applicable contributory drainage area limitation specified at § 175-172N.(2). (b) Designed to infiltrate into the subsoil. (c) Designed with underdrains, where stormwater percolates into the underdrain through the soils and is not directed to the underdrain by an outlet control structure. (d) Designed to maintain at least a ten-foot wide area of native vegetation along at least 50 percent of the shoreline and to include a stormwater runoff retention component designed to capture stormwater runoff for beneficial reuse, such as irrigation. (e) Designed with a slope of less than two percent. (f) Designed with a slope of equal to or greater than two percent. (g) Manufactured treatment devices that meet the definition of green infrastructure at § 175-171. (h) Manufactured treatment devices that do not meet the definition of green infrastructure at § 175-171. (i) The top elevation of the impermeable layer or liner must maintain this two-foot minimum separation to the seasonal high water table. |
F. An alternative stormwater management measure, alternative removal rate, and/or alternative method to calculate the removal rate may be used if the design engineer demonstrates the capability of the proposed alternative stormwater management measure and/or the validity of the alternative rate or method to the municipality. A copy of any approved alternative stormwater management measure, alternative removal rate, and/or alternative method to calculate the removal rate shall be provided to the NJDEP and the Pinelands Commission in accordance with § 175-174B. Alternative stormwater management measures may be used to satisfy the requirements at § 175-172N. only if the measures meet the definition of green infrastructure at § 175-171. Alternative stormwater management measures that function in a similar manner to a BMP listed at § 175-172N.(2) are subject to the contributory drainage area limitation specified at § 175-172N.(2) for that similarly functioning BMP. Alternative stormwater management measures approved in accordance with this subsection that do not function in a similar manner to any BMP listed at § 175-172N.(2) shall have a contributory drainage area less than or equal to two and one-half acres, except for alternative stormwater management measures that function similarly to cisterns, grass swales, green roofs, standard constructed wetlands, vegetative filter strips, and wet ponds, which are not subject to a contributory drainage area limitation. Alternative measures that function similarly to standard constructed wetlands or wet ponds shall not be used for compliance with the stormwater runoff quality standard unless a variance in accordance with § 175-179 is granted from § 175-172N.
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G. Hydraulic impacts.
(1) For all major development, groundwater mounding analysis shall be required for purposes of assessing the hydraulic impacts of mounding of the water table resulting from infiltration of stormwater runoff from the maximum storm designed for infiltration. The mounding analysis shall provide details and supporting documentation on the methodology used. Groundwater mounds shall not cause stormwater or groundwater to breakout to the land surface or cause adverse impacts to adjacent water bodies, wetlands, or subsurface structures, including, but not limited to, basements and septic systems. Where the mounding analysis identifies adverse impacts, the stormwater management measure shall be redesigned or relocated, as appropriate.
(2) For all applicable minor development, a design engineer's certification that each green infrastructure stormwater management measure will not adversely impact basements or septic systems of the proposed development shall be required.
H. Design standards for stormwater management measures are as follows:
(1) Stormwater management measures shall be designed to take into account the existing site conditions, including, but not limited to, environmentally critical areas; wetlands; wetland transition areas; flood-prone areas; slopes; depth to seasonal high water table; soil type, permeability, and texture; drainage area and drainage patterns; and the presence of solution-prone carbonate rocks (limestone);
(2) Stormwater management measures designed to infiltrate stormwater shall be designed, constructed, and maintained to provide a minimum separation of at least two feet between the elevation of the lowest point of infiltration and the seasonal high water table;
(3) Stormwater management measures designed to infiltrate stormwater shall be sited in suitable soils verified by testing to have permeability rates between one and 20 inches per hour. A factor of safety of two shall be applied to the soil's permeability rate in determining the infiltration measure's design permeability rate. If such soils do not exist on the parcel proposed for development or if it is demonstrated that it is not practical for engineering, environmental, or safety reasons to site the stormwater infiltration measure(s) in such soils, the stormwater infiltration measure(s) may be sited in soils verified by testing to have permeability rates in excess of 20 inches per hour, provided that stormwater is routed through a bioretention system prior to infiltration. Said bioretention system shall be designed, installed, and maintained in accordance with the New Jersey Stormwater BMP Manual;
(4) The use of stormwater management measures that are smaller in size and distributed spatially throughout a parcel, rather than the use of a single, larger stormwater management measure shall be required;
(5) Methods of treating stormwater prior to entering any stormwater management measure shall be incorporated into the design of the stormwater management measure to the maximum extent practical;
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(6) To avoid sedimentation that may result in clogging and reduction of infiltration capability and to maintain maximum soil infiltration capacity, the construction of stormwater management measures that rely upon infiltration shall be managed in accordance with the following standards:
(a) No stormwater management measure shall be placed into operation until its drainage area has been completely stabilized. Instead, upstream runoff shall be diverted around the measure 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 N.J.A.C. 2:90;
(b) If, for engineering, environmental, or safety reasons, temporary stormwater management facilities and sediment basins cannot be constructed on the parcel in accordance with (a) above, the stormwater management measure may be placed into operation prior to the complete stabilization of its drainage area provided that the measure's bottom during this period is constructed at a depth at least two feet higher than its final design elevation. When the drainage area has been completely stabilized, all accumulated sediment shall be removed from the stormwater management measure, which shall then be excavated to its final design elevation; and
(c) To avoid compacting the soils below a stormwater management measure designed to infiltrate stormwater, no heavy equipment, such as backhoes, dump trucks, or bulldozers shall be permitted to operate within the footprint of the stormwater management measure. All excavation required to construct a stormwater management measure that relies on infiltration shall be performed by equipment placed outside the footprint of the stormwater management measure. If this is not possible, the soils within the excavated area shall be renovated and tilled after construction is completed. Earthwork associated with stormwater management measure construction, including excavation, grading, cutting, or filling, shall not be performed when soil moisture content is above the lower plastic limit;
(7) Dry wells shall be designed to prevent access by amphibian and reptiles;
(8) Stormwater management measures shall be designed to minimize maintenance, facilitate maintenance and repairs, and ensure proper functioning. Trash racks shall be installed at the intake to the outlet structure, as appropriate, and shall have parallel bars with one-inch spacing between the bars to the elevation of the water quality design storm established at § 175-172P.(4). For elevations higher than the water quality design storm, the parallel bars at the outlet structure shall be spaced no greater than one-third the width of the diameter of the orifice or one-third the width of the weir, with a minimum spacing between bars of one inch and a maximum spacing between bars of six inches. In addition, the design of trash racks must comply with the requirements of § 175-176C.(1);
(9) Stormwater management measures shall be designed, constructed, and installed to be strong, durable, and corrosion resistant. Measures that are consistent with the relevant portions of the residential site improvement standards at N.J.A.C. 5:21-7.3, 7.4, and 7.5 shall be deemed to meet this requirement;
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(10) Stormwater management BMPs shall be designed to meet the minimum safety standards for stormwater management BMPs at § 175-176; and
(11) The size of the orifice at the intake to the outlet from the stormwater management BMP shall be a minimum of two and one-half inches in diameter.
I. Manufactured treatment devices may be used to meet the requirements of this article, provided the pollutant removal rates are verified by the New Jersey Corporation for Advanced Technology and certified by the NJDEP. Manufactured treatment devices that do not meet the definition of green infrastructure at § 175-171 may be used only under the circumstances described at § 175-172N.(4).
J. Any application for a new agricultural development that meets the definition of major development at N.J.A.C. 7:8-1.2 shall be submitted to the Soil Conservation District for review and approval in accordance with the requirements at § 175-172N., O., P., and Q. and any applicable Soil Conservation District guidelines for stormwater runoff quantity and erosion control. For purposes of this subsection, "agricultural development" means land uses normally associated with the production of food, fiber, and livestock for sale. Such uses do not include the development of land for the processing or sale of food and the manufacture of agriculturally related products.
K. If there is more than one drainage area, the groundwater recharge, stormwater runoff quality, and stormwater runoff quantity standards at § 175-172O., P., and Q. shall be met in each drainage area, unless the runoff from the drainage areas converge onsite and no adverse environmental impact would occur as a result of compliance with any one or more of the individual standards being determined utilizing a weighted average of the results achieved for that individual standard across the affected drainage areas.
L. Any stormwater management measure authorized under the municipal stormwater management plan or this article shall be reflected in a deed notice recorded in the Atlantic County Clerk's Office. A form of deed notice shall be submitted to the municipality for approval prior to filing. The deed notice shall contain a description of the stormwater management measure(s) used to meet the green infrastructure, groundwater recharge, stormwater runoff quality, and stormwater runoff quantity standards at § 175-172N., O., P., and Q. and shall identify the location of the stormwater management measure(s) in NAD 1983 State Plane New Jersey FIPS 2900 US Feet or Latitude and Longitude in decimal degrees. The deed notice shall also reference the maintenance plan required to be recorded upon the deed pursuant to § 175-178B.(5). Prior to the commencement of construction, proof that the above required deed notice has been filed shall be submitted to the municipality. Proof that the required information has been recorded on the deed shall be in the form of either a copy of the complete recorded document or a receipt from the clerk or other proof of recordation provided by the recording office. However, if the initial proof provided to the municipality is not a copy of the complete recorded document, a copy of the complete recorded document shall be provided to the municipality within 180 calendar days of the authorization granted by the municipality.
M. A stormwater management measure approved under the municipal stormwater management plan or this article may be altered or replaced with the approval of the municipality, if the municipality determines that the proposed alteration or replacement meets the design and
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performance standards contained in § 175-172N., O., P., and Q. and provides the same level of stormwater management as the previously approved stormwater management measure that is being altered or replaced. If an alteration or replacement is approved, a revised deed notice shall be submitted to the municipality for approval and subsequently recorded with the Atlantic County Clerk's Office and shall contain a description and location of the stormwater management measure, as well as reference to the maintenance plan, in accordance with L above. Prior to the commencement of construction, proof that the above required deed notice has been filed shall be submitted to the municipality in accordance with L. above.
N. Green infrastructure standards.
(1) This subsection specifies the types of green infrastructure BMPs that may be used to satisfy the groundwater recharge, stormwater runoff quality, and stormwater runoff quantity standards of this article.
(2) To satisfy the groundwater recharge and stormwater runoff quality standards at § 175-172O. and P., the design engineer shall utilize BMPs identified in Table 1 at § 175-172E. and/or an alternative stormwater management measure approved in accordance with § 175-172F. The following green infrastructure BMPs are subject to the following maximum contributory drainage area limitations:
Best Management Practice | Maximum Contributory Drainage Area |
Dry well | 1 acre |
Manufactured treatment device | 2.5 acres |
Pervious pavement system | Area of additional inflow cannot exceed three times the area occupied by the BMP |
Small-scale bioretention systems | 2.5 acres |
Small-scale infiltration basin | 2.5 acres |
Small-scale sand filter | 2.5 acres |
(3) To satisfy the stormwater runoff quantity standards at § 175-172Q., the design engineer shall utilize BMPs identified in Table 1 or 2 at § 175-172E. and/or an alternative stormwater management measure approved in accordance with § 175-172F.
(4) If a variance in accordance with § 175-179. is granted from the requirements of this subsection, then BMPs from Table 1, 2, or 3 at § 175-172E. and/or an alternative stormwater management measure approved in accordance with § 175-172F. may be used to meet the groundwater recharge, stormwater runoff quality, and stormwater runoff quantity standards at § 175-172O., P., and Q.
(5) For separate or combined storm sewer improvement projects, such as sewer separation, undertaken by a government agency or public utility (for example, a sewerage company), the requirements of this subsection shall only apply to areas owned in fee
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simple by the government agency or utility, and areas within a right-of-way or easement held or controlled by the government agency or utility; the entity shall not be required to obtain additional property or property rights to fully satisfy the requirements of this subsection. Regardless of the amount of area of a separate or combined storm sewer improvement project subject to the green infrastructure requirements of this subsection, each project shall fully comply with the applicable groundwater recharge, stormwater runoff quality control, and stormwater runoff quantity standards at § 175-172O., P., and Q.
O. Groundwater recharge standards.
(1) This subsection contains the minimum design and performance standards for groundwater recharge as follows:
(2) For all major development, the total runoff volume generated from the net increase in impervious surfaces by a ten-year, 24-hour storm shall be retained and infiltrated onsite.
(3) For minor development that involves the construction of four or fewer dwelling units, the runoff generated from the total roof area of the dwelling(s) by a ten-year, 24-hour storm shall be retained and infiltrated through installation of one or more green infrastructure stormwater management measures designed in accordance with the New Jersey Stormwater BMP Manual. Appropriate green infrastructure stormwater management measures include, but are not limited to dry wells, pervious pavement systems, and small scale bioretention systems, including rain gardens.
(4) For minor development that involves any nonresidential use and will result in an increase of greater than 1,000 square feet of regulated motor vehicle surfaces, the water quality design storm volume generated from these surfaces shall be recharged onsite.
(5) Stormwater from areas of high pollutant loading and/or industrial stormwater exposed to source material shall only be recharged in accordance with § 175-172P.(8).
P. Stormwater runoff quality standards.
(1) This subsection contains the minimum design and performance standards to control stormwater runoff quality impacts of:
(a) Major development;
(b) Minor development that involves any nonresidential use and will result in an increase of greater than 1,000 square feet of regulated motor vehicle surfaces; and
(c) Any development involving the grading, clearing, or disturbance of an area in excess of 5,000 square feet within any five-year period.
(2) Stormwater management measures shall be designed to reduce the post-construction load of total suspended solids (TSS) in stormwater runoff generated from the water quality design storm established at § 175-172P.(4) as follows:
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(a) Eighty percent TSS removal of the anticipated load, expressed as an annual average shall be achieved for the stormwater runoff from the net increase of motor vehicle surface.
(b) If the surface is considered regulated motor vehicle surface because the water quality treatment for an area of motor vehicle surface that is currently receiving water quality treatment either by vegetation or soil, by an existing stormwater management measure, or by treatment at a wastewater treatment plant is to be modified or removed, the project shall maintain or increase the existing TSS removal of the anticipated load expressed as an annual average.
(3) The requirement to reduce TSS does not apply to any stormwater runoff in a discharge regulated under a numeric effluent limitation for TSS imposed under the New Jersey Pollutant Discharge Elimination System (NJPDES) rules, N.J.A.C. 7:14A, or in a discharge specifically exempt under a NJPDES permit from this requirement. Every major development, including any that discharge into a combined sewer system, shall comply with (2) above, unless the major development is itself subject to a NJPDES permit with a numeric effluent limitation for TSS or the NJPDES permit to which the major development is subject exempts the development from a numeric effluent limitation for TSS.
(4) The water quality design storm is 1.25 inches of rainfall in two hours. Water quality calculations shall take into account the distribution of rain from the water quality design storm, as reflected in Table 4, below. The calculation of the volume of runoff may take into account the implementation of stormwater management measures.
Table 4: Water Quality Design Storm Distribution
Time (Minutes) | Cumulative Rainfall (Inches) | Time (Minutes) | Cumulative Rainfall (Inches) | Time (Minutes) | Cumulative Rainfall (Inches) |
1 | 0.00166 | 41 | 0.1728 | 81 | 1.0906 |
2 | 0.00332 | 42 | 0.1796 | 82 | 1.0972 |
3 | 0.00498 | 43 | 0.1864 | 83 | 1.1038 |
4 | 0.00664 | 44 | 0.1932 | 84 | 1.1104 |
5 | 0.0083 | 45 | 0.2 | 85 | 1.117 |
6 | 0.00996 | 46 | 0.2117 | 86 | 1.1236 |
7 | 0.01162 | 47 | 0.2233 | 87 | 1.1302 |
8 | 0.01328 | 48 | 0.235 | 88 | 1.1368 |
9 | 0.01494 | 49 | 0.2466 | 89 | 1.1434 |
10 | 0.0166 | 50 | 0.2583 | 90 | 1.15 |
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Time (Minutes) | Cumulative Rainfall (Inches) | Time (Minutes) | Cumulative Rainfall (Inches) | Time (Minutes) | Cumulative Rainfall (Inches) |
11 | 0.01828 | 51 | 0.2783 | 91 | 1.155 |
12 | 0.01996 | 52 | 0.2983 | 92 | 1.16 |
13 | 0.02164 | 53 | 0.3183 | 93 | 1.165 |
14 | 0.02332 | 54 | 0.3383 | 94 | 1.17 |
15 | 0.025 | 55 | 0.3583 | 95 | 1.175 |
16 | 0.03 | 56 | 0.4116 | 96 | 1.18 |
17 | 0.035 | 57 | 0.465 | 97 | 1.185 |
18 | 0.04 | 58 | 0.5183 | 98 | 1.19 |
19 | 0.045 | 59 | 0.5717 | 99 | 1.195 |
20 | 0.05 | 60 | 0.625 | 100 | 1.2 |
21 | 0.055 | 61 | 0.6783 | 101 | 1.205 |
22 | 0.06 | 62 | 0.7317 | 102 | 1.21 |
23 | 0.065 | 63 | 0.785 | 103 | 1.215 |
24 | 0.07 | 64 | 0.8384 | 104 | 1.22 |
25 | 0.075 | 65 | 0.8917 | 105 | 1.225 |
26 | 0.08 | 66 | 0.9117 | 106 | 1.2267 |
27 | 0.085 | 67 | 0.9317 | 107 | 1.2284 |
28 | 0.09 | 68 | 0.9517 | 108 | 1.23 |
29 | 0.095 | 69 | 0.9717 | 109 | 1.2317 |
30 | 0.1 | 70 | 0.9917 | 110 | 1.2334 |
31 | 0.1066 | 71 | 1.0034 | 111 | 1.2351 |
32 | 0.1132 | 72 | 1.015 | 112 | 1.2367 |
33 | 0.1198 | 73 | 1.0267 | 113 | 1.2384 |
34 | 0.1264 | 74 | 1.0383 | 114 | 1.24 |
35 | 0.133 | 75 | 1.05 | 115 | 1.2417 |
36 | 0.1396 | 76 | 1.0568 | 116 | 1.2434 |
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Time (Minutes) | Cumulative Rainfall (Inches) | Time (Minutes) | Cumulative Rainfall (Inches) | Time (Minutes) | Cumulative Rainfall (Inches) |
37 | 0.1462 | 77 | 1.0636 | 117 | 1.245 |
38 | 0.1528 | 78 | 1.0704 | 118 | 1.2467 |
39 | 0.1594 | 79 | 1.0772 | 119 | 1.2483 |
40 | 0.166 | 80 | 1.084 | 120 | 1.25 |
(5) If more than one BMP in series is necessary to achieve the required 80 percent TSS reduction for a site, the applicant shall utilize the following formula to calculate TSS reduction:
R = A + B - (A x B) / 100
Where,
R = total TSS Percent Load Removal from application of both BMPs
A = the TSS Percent Removal Rate applicable to the first BMP
B = the TSS Percent Removal Rate applicable to the second BMP
(6) Stormwater management measures shall also be designed to reduce, to the maximum extent feasible, the post-construction nutrient load of the anticipated load from the developed site in stormwater runoff generated from the water quality design storm established at § 175-172P.(4). In achieving reduction of nutrients to the maximum extent feasible, the design of the site shall include green infrastructure BMPs that optimize nutrient removal while still achieving the performance standards in § 175-172O., P., and Q.
(7) For all major development, stormwater management measures shall be designed to achieve a minimum of 65 percent reduction of the post-construction total nitrogen load from the developed site, including those permanent lawn or turf areas that are specifically intended for active human use as described at N.J.A.C. 7:50-6.24(c)3, in stormwater runoff generated from the water quality design storm established at § 175-172P.(4). In achieving a minimum 65 percent reduction of total nitrogen, the design of the site shall include green infrastructure in accordance with the New Jersey Stormwater BMP Manual and shall optimize nutrient removal. The minimum 65 percent total nitrogen reduction may be achieved by using a singular stormwater management measure or multiple stormwater management measures in series.
(8) In high pollutant loading areas (HPLAs) and/or areas where stormwater runoff is exposed to source material, as defined in § 175-171, the following additional water quality standards shall apply:
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(a) The areal extent and amount of precipitation falling directly on or flowing over HPLAs and/or areas where stormwater is exposed to source material shall be minimized through the use of roof covers, canopies, curbing or other physical means to the maximum extent practical in order to minimize the quantity of stormwater generated from HPLA areas and areas where stormwater runoff is exposed to source material;
(b) The stormwater runoff originating from HPLAs and/or areas where stormwater runoff is exposed to source material shall be segregated and prohibited from co-mingling with stormwater runoff originating from the remainder of the parcel unless it is first routed through one or more stormwater management measures required at (c) below;
(c) The stormwater runoff from HPLAs and/or areas where stormwater runoff is exposed to source material shall incorporate stormwater management measures designed to reduce the post-construction load of TSS by at least 90 percent in stormwater runoff generated from the water quality design storm established at § 175-172P.(4) using one or more of the measures identified at [1] or [2] below. In meeting this requirement, the minimum 90 percent removal of total suspended solids may be achieved by utilizing multiple stormwater management measures in series:
[1] Any measure designed in accordance with the New Jersey Stormwater BMP Manual to remove total suspended solids. Any such measure must be constructed to ensure that the lowest point of infiltration within the measure maintains a minimum of two feet of vertical separation from the seasonal high-water table; and
[2] Other measures certified by the NJDEP, including a media filtration system manufactured treatment device with a minimum 80 percent removal of total suspended solids as verified by the New Jersey Corporation for Advanced Technology; and
(d) If the potential for contamination of stormwater runoff by petroleum products exists onsite, prior to being conveyed to the stormwater management measure required at (c) above, the stormwater runoff from the HPLAs and areas where stormwater runoff is exposed to source material shall be conveyed through an oil/grease separator or other equivalent manufactured filtering device providing for the removal of petroleum hydrocarbons. The applicant shall provide the review agency with sufficient data to demonstrate acceptable performance of the device.
(9) The Flood Hazard Area Control Act Rules at N.J.A.C. 7:13-4.1(c)1 establish 300-foot riparian zones along Category One waters, as designated in the Surface Water Quality Standards at N.J.A.C. 7:9B, and certain upstream tributaries to Category One waters. A person shall not undertake a major development that is located within or discharges into a 300-foot riparian zone without prior authorization from the Department under N.J.A.C. 7:13.
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(10) Pursuant to the Flood Hazard Area Control Act Rules at N.J.A.C. 7:13-11.2(j)3.i, runoff from the water quality design storm that is discharged within a 300-foot riparian zone shall be treated in accordance with this subsection to reduce the post-construction load of total suspended solids by 95 percent of the anticipated load from the developed site, expressed as an annual average.
Q. Stormwater runoff quantity standards.
(1) This subsection contains the minimum design and performance standards to control stormwater runoff quantity impacts related to applicable major and minor development.
(2) In order to control stormwater runoff quantity impacts, the design engineer shall, using the assumptions and factors for stormwater runoff calculations at § 175-173, complete one of the following:
(a) Demonstrate through hydrologic and hydraulic analysis that for stormwater leaving the site, post-construction runoff hydrographs for the two-, ten-, and 100-year storm events do not exceed, at any point in time, the pre-construction runoff hydrographs for the same storm events;
(b) Demonstrate through hydrologic and hydraulic analysis that there is no increase, as compared to the pre-construction condition, in the peak runoff rates of stormwater leaving the site for the two-, ten- and 100-year storm events and that the increased volume or change in timing of stormwater runoff will not increase flood damage at or downstream of the site. This analysis shall include the analysis of impacts of existing land uses and projected land uses assuming full development under existing zoning and land use ordinances in the drainage area;
(c) Design stormwater management measures so that the post-construction peak runoff rates for the two-, ten- and 100-year storm events are 50, 75 and 80 percent, respectively, of the pre-construction peak runoff rates. The percentages apply only to the post-construction stormwater runoff that is attributable to the portion of the site on which the proposed development or project is to be constructed; or
(d) In tidal flood hazard areas, stormwater runoff quantity analysis in accordance with (a), (b), and (c) above is required unless the design engineer demonstrates through hydrologic and hydraulic analysis that the increased volume, change in timing, or increased rate of the stormwater runoff, or any combination of the three will not result in additional flood damage below the point of discharge of the major development. No analysis is required if the stormwater is discharged directly into any ocean, bay, inlet, or the reach of any watercourse between its confluence with an ocean, bay, or inlet and downstream of the first water control structure.
(3) The stormwater runoff quantity standards shall be applied at the site's boundary to each abutting lot, roadway, watercourse, or receiving storm sewer system.
175:373 2024 S-13
§ 175-172 HAMMONTON CODE § 175-173
(4) There shall be no direct discharge of stormwater runoff from any point or nonpoint source to any wetland, wetlands transition area, or surface waterbody. In addition, stormwater runoff shall not be directed in such a way as to increase the volume and rate of discharge into any wetlands, wetlands transition area, or surface water body from that which existed prior to development of the parcel.
(5) To the maximum extent practical, there shall be no direct discharge of stormwater runoff onto farm fields to protect farm crops from damage due to flooding, erosion, and long-term saturation of cultivated crops and cropland.
R. As-built requirements for major development are as follows:
(1) After all construction activities have been completed on the parcel and finished grade has been established in each stormwater management measure designed to infiltrate stormwater, replicate post-development permeability tests shall be conducted to determine if as-built soil permeability rates are consistent with design permeability rates. The results of such tests shall be submitted to the municipal engineer or other appropriate reviewing engineer. If the results of the post-development permeability tests fail to achieve the minimum required design permeability rate, utilizing a factor of safety of two, the stormwater management measure shall be renovated and re-tested until the required permeability rates are achieved; and
(2) After all construction activities and required testing have been completed on the parcel, as-built plans, including as-built elevations of all stormwater management measures shall be submitted to the municipal engineer or other appropriate reviewing engineer to serve as a document of record. Based upon that engineer's review of the as-built plans, all corrections or remedial actions deemed necessary due to the failure to comply with design standards and/or for any reason concerning public health or safety, shall be completed by the applicant. In lieu of review by the municipal engineer, the municipality may engage a licensed professional engineer to review the as-built plans and charge the applicant for all costs associated with such review.
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