1.Purpose and Intent
The purpose and intent of stormwater management shall include:
a. for quantitative control of stormwater runoff, consisting of a system of native specie vegetation and structural measures that control the increased volume and rate of surface runoff caused by man-made changes to the land; and
b. for qualitative control of stormwater runoff, consisting of a system of native specie vegetation, structural or other measures that reduce or eliminate pollutants that might otherwise be carried off by surface runoff.
2.Application
The applicant shall follow all regulations and policies for proper stormwater management for the following all new subdivisions.
3.Submission Requirements
The applicant shall be responsible for providing applicable information in compliance with these Rules and Regulations.
Information to be provided shall include:
A. All storm drainage information in accordance with 6.14 of the Rules and Regulations Governing the Subdivision of Land in North Andover, Massachusetts;
B. Detailed description of the existing environmental and hydrological conditions of the site and of the receiving waters and Wetland Resource Areas. This information shall include, but not be limited to, the following:
1) the direction, flow rate, and volume of surface runoff under existing conditions and, to the extent practicable, pre-development conditions;
2) the location of areas of the site where stormwater collects or percolates into the ground;
3) a description of all surface watercourses, water bodies, and Wetland Resource Areas on or entering the site, or adjacent to the site, or into which stormwater flows. Information regarding their water quality and current water qualify classification shall be included;
4) depth of seasonal groundwater levels, approximate direction and rate of flow, seasonal fluctuations;
5) location of 100 year flood zones/plains;
6) principal vegetation types;
7) topography described in full contour detail, at two (2) foot intervals, with area of steep slope (over 10%) highlighted;
8) soils, with an accompanying analysis of the best use potential of the soils and the hydrological group classification: the soil map and use potentials analysis prepared by the U.S. Soil Conservation Service shall be used as the basis for this analysis.
C. Proposed alterations of the site shall be described in detail including, but not limited to, the following:
1) changes in topography, described in full contour, with details at two (2) foot intervals;
2) areas where vegetation will be cleared or otherwise altered;
3) areas that will be covered with an impervious surface and a description of the surfacing material(s);
D. The proposed development layout shall be described in detail including, but not limited to, the following:
1) the site arrangement including the location of structures, roadways, parking areas, sewage disposal facilities and undisturbed lands;
2) all drainage systems to be provided, including the location and design of the roadway and individual lot subdrains and full drainage calculations and supporting documentation;
E. Predicted impacts of the proposed development on existing conditions shall be described in detail and shall include:
1) changes in water quality including, but not limited to, ground and surface water;
2) changes in groundwater levels;
3) changes in the incidence and duration of flooding on the site and upstream and downstream from it;
4) adverse impacts on Wetland Resource Areas;
5) impacts on vegetation.
F. All components of the drainage system and any measures for the detention, retention or infiltration of water and/or for the protection of water quality shall be described in detail, including the following:
1) the channel, direction, volume and rate of flow and the quality of stormwater that will be conveyed from the site, with a comparison to existing conditions and to the extent practicable, pre-development conditions;
2) detention and retention areas and devices, including:
i) plans for discharge of contained waters, including the time to draw down from full condition, and description of outlet structures;
ii) maintenance plans: including maintenance schedule, an outline of responsible parties and owners, and all pertinent information and/or agreements to be executed to insure proper maintenance;
iii)an evaluation of the pollutant removal efficiency of such devices under the existing conditions;
3) areas of the site to be used or reserved for percolation including the depth to seasonal groundwater table, and prediction of the impact on groundwater quality;
4) areas to be utilized in overland flow, the hydrological soil type of such areas, vegetation present, and the soil susceptibility to erosion;
5) any other information which the Applicant or the Planning Board believes is necessary for an evaluation of the development.
G. Nitrogen and/or Phosphorus Loading Report: For review of water quality impact, an Applicant shall submit calculations of anticipated nitrogen and/or phosphorus contribution from roads, lawns and septic systems. The Applicant must determine the "carrying load" or ability to absorb nitrogen and phosphorus loading of all receiving water systems on site.
4. Performance Standards:
The Stormwater Management Report submitted must demonstrate that the proposed development or activity has been planned and designed and shall be constructed and maintained, to the extent that is reasonably possible, to meet each of the following standards:
a. ensure that after development that no detrimental effects shall be created or caused by the proposed development.
b. maintain the natural hydrodynamic characteristics of the watershed;
c. protect or improve the quality of surface and ground waters;
d. protect, maintain, or improve water quality or existing water quality standards for all receiving waters, water courses and water bodies;
e. protect and maintain groundwater levels;
f. protect the beneficial functioning of Wetland Resource Areas as areas for natural storage of flood waters, the chemical reduction and assimilation of pollutants and wildlife and fisheries habitat;
g. prevent increased flooding and damage that results from improper location, construction and design of structures;
h. prevent reverse salt water intrusion;
i. protect the natural fluctuating levels of salinity in estuarine areas;
j. minimize alteration to flora and fauna and adverse impacts to fish and wildlife habitat;
k. otherwise further the objectives of the Stormwater Management Policies and Regulations.
5. Design Standards
The design, construction and maintenance of stormwater systems shall be consistent with the following:
a. Discharging runoff directly into rivers, streams, watercourses, or enlarging the volume, rate or further degrading the quality of existing discharges/runoff is prohibited. Runoff shall be routed through vegetated swales, using native species and other structural and nonstructural systems designed to increase time of concentration, decrease velocity, increase infiltration, allow suspended solids to settle and remove pollutants. Such systems will utilize overland flow and re-infiltration as priority techniques for the treatment of run-off;
b. Retention and detention ponds, and methods of overland flow may be used to retain, detain and treat the increased and accelerated runoff which the development generates;
c. There shall be a minimum of two (2') feet of naturally occurring soils between the detention basin bottom and the maximum annual ground water table;
d. Water shall be released from detention ponds at a rate and in a manner approximating the natural conditions which would have occurred before development;
e. Intermittent water courses such as swales shall be vegetated;
f. The first one (1") inch of runoff from impervious surfaces, such as rooftops and paved surfaces, shall be treated in the site of the development;
g. Runoff from parking lots and streets shall be treated to remove oil and sediments. Catch basins shall be provided with hoods; in the alternative, drainage outfalls shall discharge to low velocity "vegetated treatment" swales.
h. The use of drainage facilities and vegetated buffer zones as open space and conservation areas shall be encouraged;
i. Neighboring properties shall not be effected by flooding from excessive runoff.
6. Detention/Retention Basins:
a. Performance Standards:
The performance standards shall include the following:
i) Development shall be oriented to the site so that cutting and stripping of vegetation and grading are minimized;
ii) Temporary seeding, mulching or other suitable stabilization methods shall be used to protect exposed soil areas during construction; as feasible, natural vegetation shall be retained and protected; during the months of October through March, when seeding and sodding my be impractical, an anchored mulch shall be applied as approved by the Board or by the Board's Designee; diversions and/or prepared outlets may be required in critical areas during construction.
iii) Soil and other materials shall not be stockpiled or redistributed, either temporarily or permanently, in locations or in such a manner as would cause suffocation of tree root systems;
iv) Erosion and sediment controls shall be coordinated with the sequence of grading, development and construction operations; control measures shall be in effect prior to commencement of each increment/phase of the process;
v) No area shall be cleared larger than that portion on which construction can be completed rapidly; large areas shall not be left bare and exposed for long periods of time;
vi) Grading shall be kept to a minimum; tree removal shall be minimized;
vii) Runoff shall be controlled and conveyed into storm drains and other outlets so it will not erode the land or cause off-site damage; sediment in runoff shall be trapped by using staked hay bales, silt fencing, or sedimentation traps;
viii) Sediment basins shall be constructed where necessary to detain runoff and to trap sediment during construction;
ix) Permanent vegetation and erosion control structures, as necessary, shall be installed preferably immediately after construction is completed but otherwise no later than the first full spring season immediately thereafter; they shall comply with the erosion and sedimentation vegetative practices recommended by the U.S. Soil Conservation Service;
x) Temporary ground cover or erosion/sedimentation controls shall be established on any unbuilt lots as required by the Board;
xi) Native species shall be used for re-vegetation;
xii) All graded areas beyond the Street Right-of-Way shall be covered with four (4") inches of topsoil and planted with a native specie of vegetative cover, sufficient to prevent erosion;
xiii)Topsoil shall be stripped from disturbed areas, stockpiled in approved areas and stabilized with temporary vegetative cover if it is to be left for more than thirty (30) calendar days; perimeter sediment controls shall be installed around each area of stockpiled topsoil.
i) Soil erosion control structures shall not be located in a front yard or side yard bordering a street;
ii) Structures should be designed to preclude the necessity for perimeter security fencing;
iii) The slope of any bank should not be greater than three (3) to one (1);
iv) The greatest depth of water in a detention pond during a 100-year design storm shall not exceed four (4) feet; release rates shall comply with the provisions of Section 6.14.3 of the Rules and Regulations Governing the Subdivision of Land in North Andover, Mass; and
v)Groundwater recharge systems shall be utilized whenever feasible.
c. Maintenance Standards - Prior to Acceptance
i) As required by the Board, all control structures and associated systems shall be inspected for functionality and damage at least twice each year by the Board's Subdivision Inspector or an agent of the Town. The costs for such inspection shall be paid by the Applicant;
ii) The Applicant shall be responsible for cleaning sediment and debris from catch basins at least annually; additional cleaning may be required by the Board;
iii) The Applicant shall be responsible for removal of trees, bushes and /or other growth in the sedimentation basins, and for keeping live native specie vegetative cover on the banks of such basins. Replacement for dead vegetative cover and re-seeding shall be completed promptly;
iv) The Applicant shall repair or replace any damaged system to the satisfaction of the Board; the Applicant shall be responsible for any damage due to flaws in design or construction; and
v)The Applicant shall be responsible for cosmetic maintenance such as periodic mowing of grassed areas in sedimentation basins.
d. Acceptance of the System
i)Prior to any acceptance by the Town or by another entity, the control structures shall be subject to a final inspection by the Board's Subdivision Inspector and/or the Town's agent; the cost of inspection shall be paid by the Applicant; the inspection shall assure compliance with the following elements:
a. the system has been constructed in accordance with the plans approved by the Board;
b. all construction debris has been removed;
c. sediment has been flushed from pipes by a pressure wash;
d. catch basins and detention/retention structures are free of sediment and
e. ground cover is fully established on slopes.
ii)No release of security for erosion and sedimentation control measures shall be granted until the Board is satisfied that the systems comply with the plans;
iii)If as a result of the final inspection the Applicant is found to be in non- compliance with the plans, the Board may use the security to assure that the control system(s) is/are brought in to conformance and is/are cleaned and maintained properly in accordance with the plans.
7.General Requirements
The Applicant shall secure future maintenance of the stormwater system by a proper bond or by a deposit or money of an amount as determined by the Board. Such security must be established to the satisfaction of the Board prior to release of any lots within the development and prior to the Board's sign-off of building permit.
In the event that the applicant does not follow maintenance procedures and programs as approved by the Board, the Board shall have the authority to expend any portion of said security to provide such maintenance.
In the event that the stormwater system is accepted by the Town or any private association and/or trust, and, therefore the Town or a private association and/or trust, assumes the ownership of said system, any remaining portion of this security may be refunded to the applicant or the homeowner's association as deemed appropriate by the Board.
