Words in all CAPITAL LETTERS are those with special definitions as noted in §
276-2 of the LAND USE REGULATIONS.
As used in this regulation, the terms listed in §
276-2 of the Land Use Regulations shall have the meanings indicated therein.
APPLICANT
The person, persons, corporation or other legal entity, or
their assigns, applying for a Site Plan, Subdivision, Excavation,
Driveway and/or Stormwater Management Permit.
BEST MANAGEMENT PRACTICE
A proven or accepted structural, nonstructural, or vegetative
measure, as described in the New Hampshire Stormwater Manual (as amended)
which reduces erosion, peak runoff rate or volume, or improves the
quality of stormwater runoff.
CRITICAL AREA
Disturbed area of any size within 50 feet of a stream, bog,
water body, or poorly or very poorly drained soils; or disturbed areas
exceeding 2,000 square feet in highly erodible soils; or disturbed
areas of more than 25 feet in length on slopes greater than 10%.
DEVELOPMENT
Any construction or land disturbance or grading activities
other than for agricultural and silvicultural practices.
DISCONNECTED IMPERVIOUS COVER
Impervious cover that directs stormwater runoff to on-site
vegetated areas to allow infiltration into the soil or be filtered
by overland flow such that the stormwater is not directly released
from a site to off-site drainage infrastructure or adjacent water
bodies or wetlands.
DISTURBANCE
Any grading, excavation or other land disturbance activity
for the purpose of development or redevelopment and not part of any
routine maintenance activity associated with existing developed areas.
EFFECTIVE IMPERVIOUS AREA
Impervious cover that discharges stormwater runoff directly
to other paved surfaces, off-site drainage infrastructure or adjacent
water bodies or wetlands.
GROUNDWATER RECHARGE VOLUME (GRv)
Volume of runoff to be infiltrated based on existing soils
as calculated in accordance with N.H. Code Admin. R. Part Env-Wq 1504.12.
IMPERVIOUS SURFACE
Any surface that prevents or significantly impedes infiltration
of water into the underlying soil. This includes, but is not limited
to, buildings, rooftops, asphalt or concrete paved areas, artificial
turf and compacted gravel or soil resulting from vehicle traffic.
LOW-IMPACT DEVELOPMENT (LID)
Low-impact development consists of site planning and design
strategies intended to maintain or replicate predevelopment hydrology
through the use of site planning, source control, and small-scale
practices integrated throughout the site to prevent, infiltrate and
manage runoff as close to its source as possible. Examples of LID
strategies are pervious pavement, rain gardens, green roofs, bioretention
basins and swales, filtration trenches, and other functionally similar
BMPs located near the runoff source.
NEW DEVELOPMENT
Any proposed construction, land alteration or site grading
on an existing undeveloped parcel or a developed parcel with less
than 40% of the parcel area comprised of impervious surfaces.
QUALIFIED PROFESSIONAL
A person knowledgeable in the principles and practice of
stormwater management and erosion and sedimentation control, including
a Certified Professional in Erosion and Sediment Control (CPESC),
a Certified Professional in Storm Water Quality (CPSWQ) or a licensed
Professional Engineer (PE).
REDEVELOPMENT
Any construction, land alteration, or improvement of any
existing parcel that is already developed and has 40% or more the
parcel area comprised of impervious surfaces. Alterations and improvements
may include proposed disturbances to existing impervious area (including
demolition and removal of road/parking lot materials down to the erodible
subbase).
STABILIZED SOIL
A.
When the soil erosion rate approaches that of undisturbed soils.
soils which are disturbed shall be considered protected when covered
with a healthy and stabilized when one of the following is achieved:
(1)
A minimum of 85% vegetative cover has been established;
(2)
A minimum of 3 inches of non-erosive material such as stone
or riprap has been placed; or
(3)
Erosion control blankets have been installed in accordance with
Env-Wq 1506.03.
B.
Note: Measures listed under Subsections
A(2) and
(3) are considered temporary and ultimately, the site needs to be fully vegetated or have a non-erodible surface.
WATER QUALITY VOLUME
Volume of runoff to be retained or treated as calculated
in accordance with N.H. Code Admin. R. Part Env-Wq 1504.10.
The design shall conform to the standards set forth in NHDES
NH Stormwater Manual (as amended), or as directed in the Land Use
Regulations, whichever dictates the higher standard.
A. Temporary/Construction
Stormwater Management Design. The following standards shall be applied
in planning for stormwater management and erosion control as it relates
to construction. If a Stormwater Pollution Prevention Plan (SWPPP)
has been prepared to comply with the EPA Construction General Permit
(CGP), the SWPPP can also be utilized to satisfy related portions
of the required SMECP contents, provided that the listed required
elements are included in the SWPPP.
(1) The
selection, sizing, installation and maintenance of all erosion and
sediment control measures included in the SMECP shall meet, as a minimum,
the Best Management Practice design guidance set forth in the NH Stormwater
Management Manual (Vols. 1, 2, and 3, as amended).
(2) Whenever
practical, natural vegetation shall be retained, protected and/or
supplemented. The clearing of vegetation shall be done in a manner
that minimizes soil erosion. Vegetated areas to be retained should
be clearly marked and protected using construction fencing or similar
means.
(3) Soil
disturbance shall be avoided within established buffer setbacks as
established by the Town Wetland and Conservation Overlay District.
(4) The
area of disturbance shall be kept to a minimum through use of Low-Impact
Development (LID) site design and treatment methods to preserve and
protect the integrity of existing natural resources to the maximum
extent practical.
(5) Construction
site disturbance should be limited to only disturb the area necessary
for a particular construction activity or phase of development especially
in winter months.
(6) Adequate
temporary solid waste and sanitary waste disposal facilities shall
be maintained on site during the construction period, as necessary.
(7) Adequate
construction stone access pads shall be installed and maintained at
site entrance and exit locations to prevent mud and sediment from
being tracked on to pavement.
(8) An
on-site pre-construction meeting shall be held with the TOWN ENGINEER
or designated representative prior to initiating earth moving activities
and after perimeter erosion control measures, protective fencing,
waste disposal and construction access pads have been installed.
(9) Disturbed
soil areas that will remain idle for more than 30 days shall be temporarily
stabilized as soon as practicable but no later than five days from
the initial disturbance with seed and mulch, erosion control blankets
or crushed stone or other suitable measures approved by the TOWN ENGINEER
or designated representative. All disturbed soil areas that have achieved
final grading shall be permanently stabilized within three days following
final grading.
(10) Up-gradient
surface runoff from undisturbed areas shall be diverted away from
disturbed areas where feasible or carried non-erosively through the
project area. Integrity of downstream drainage systems shall be maintained.
(11) Natural
drainage patterns and conveyances, including intermittent streams,
swales, and drainage ditches shall be maintained to the extent practical
to convey runoff from the project area. Perimeter controls shall not
be placed within wetlands or intermittent and perennial stream channels.
(12) Disturbed
areas that will remain idle over the winter period shall employ winter
stabilization measures as described in Section 4-3 of the NH Stormwater
Manual, Volume 3, as amended.
(13) All
erosion and sediment control measures shall be designed and installed
in accordance with guidelines contained in the NH Stormwater Manual,
Volume 3, as amended.
(14) All erosion control measures and related drainage ways shall be routinely inspected and maintained by a qualified professional to ensure measures remain in functioning condition until final site stabilization is accomplished. See §
290-6 .
(15) All
temporary erosion and sediment control measures and accumulated sediment
shall be removed after final site stabilization.
The following are minimum technical details to be included in
stormwater management and erosion control plans (SMECP). Additional
requirements may be found in this and other sections of the Site Plan
Review and Subdivision Regulations. At the PLANNING BOARD's discretion
and in consultation with the TOWN ENGINEER, the Board may waive certain
items that are not relevant or applicable to the proposed project
following written request by the Applicant.
A. Stormwater
Management and Erosion Control Plan (SMECP) Contents:
(1) Narrative
that describes the proposed development activity, the construction
period and timing, the proposed changes in existing land use, land
cover and changes in impervious areas and how the various local and
state stormwater management and erosion control standards will be
met.
(2) Description
of on-site and adjacent wetlands, streams and other water bodies or
natural resources and the methods used to identify these resources.
(3) Description
of Low-Impact Development (LID) practices and other protective measures
to limit impacts to adjacent natural resources and water bodies.
(4) Description
of any applicable buffer setbacks, steep slopes, critical areas, existing
mature vegetation, unique habitat conditions, 100-year floodplain
limits, man-made and natural drainage conveyances and constraints
and known water quality based on local data or the NHDES 303(d) list.
(5) Description
of the proposed erosion control and stormwater treatment measures,
dewatering methods, methods and calculations of stormwater runoff
rate and volumes and BMP sizing, demonstration of no downstream impacts,
inspection and maintenance procedures including discussion of roles
and responsibilities and contingency measures for extreme precipitation
events during construction.
(6) Calculations
for the infiltration or exfiltration system, test pit information
including estimated seasonal high-water table elevation for any proposed
infiltrating or exfiltrating device. These calculations should also
account for frozen ground conditions, when the devices may not function
at their optimal design.
(7) Any
other specific study, calculation, or investigation as requested by
the Town.
(8) The
SMECP and Drainage Plans shall be certified by a licensed professional
engineer, registered in the State of New Hampshire.
(9) An
erosion control inspection and maintenance plan that describes inspection
protocols, frequency, reporting, roles and responsibilities, contact
information and contingency plans for extreme weather events.
(10) A
long-term post-construction stormwater BMP maintenance plan that describes
inspection and maintenance procedures for all post-construction stormwater
control measures including a description of the responsible party
that will perform the long-term maintenance, reporting procedures
and process for corrective actions.
B. Pans of
both existing and proposed conditions shall present the following
items:
(2) Parcel
map showing property boundaries and any existing and proposed easements.
(3) North
arrow, scale, date and existing and proposed topographic contours
at two-foot intervals.
(4) Existing
and proposed structures, utilities, roads and limits of other paved
areas.
(5) Locations
and limits of CRITICAL AREAS within the Project Area and within 200
feet of project boundary and surface waters and wetlands.
(6) Surface
water and wetlands, drainage patterns, and watershed boundaries.
(7) Limits
of disturbance, areas of cut and fill and limits and types of existing
mature vegetation.
(8) Locations
and detail notes of the sediment and erosion control measures including,
but not limited to, temporary and permanent stabilization measures,
perimeter controls, slope stabilization, construction access pads
and spill containment measures to be used at various locations and
stages of construction.
(9) Proposed
stockpiles, equipment storage and refueling areas, and a plan for
stump and debris removal.
(10) Identify
locations and type of sanitary and solid waste disposal facilities,
if applicable.
(11) Construction
schedule, phasing and grading details.
(12) Extent
of 100-year floodplain boundaries if published or determined.
(13) Soils
information from a National Cooperative Soil Survey (NCSS) soil series
map or a High Intensity Soil Map of the site, prepared in accordance
with SSSNNE Special Publication No. 1. HIGHLY ERODIBLE SOILS shall
be determined by soil series.
(14) Identify
temporary and permanent wetland impact areas of poorly and/or very
poorly drained soils and areas proposed to be filled.
(15) Identification
of permanent stormwater treatment BMPs and associated design and sizing
details.
(16) Locations
of post-construction snow storage areas and temporary snow storage
area during construction.
(17) The
direction of flow of runoff using arrows and location, elevation,
and size of all existing and proposed catch basins, dry wells, drainage
ditches, swales, retention basins, and storm sewers shall be shown
on the plan.
(18) As
applicable, test pit log forms, subsurface inspection results and
infiltration rates.
(19) Location
and description of nearest receiving water (include at least 1/4 mile
downstream), drainage channels, conveyance systems and information
on water quality impairments.
(20) A
demonstration or explanation showing the adequate capacity of the
downstream system to handle flow conditions after Development.
(21) A
demonstration or explanation showing that the Development of the site
shall not affect the downstream systems negatively.
In addition to local approval, copies of the following permits
shall be required if applicable:
A. RSA 485-A:17
requires a PERMIT from the New Hampshire Department of Environmental
Services for "[...]any person proposing to significantly alter the
characteristics of the terrain, in such a manner as to impede the
natural runoff or create an unnatural runoff[...]". Regulations require
this PERMIT for any project involving more than 100,000 contiguous
square feet of disturbance or if such activity occurs in or on the
border of the surface waters of the state.
B. EPA's
Construction General Permit for Stormwater Discharges Associated With
Construction Activity (CGP): For a cumulative disturbance of one acre
of land that the EPA considers "construction activity," which includes,
but is not limited to, clearing, grading, excavation and other activities
that expose soil typically related to landscaping, demolition and
construction of structures and roads, a federal CGP shall be required.
Consult the EPA for specific rules. To apply, the entity or individual
responsible for construction site operations shall file a notice of
intent (NOI) with the EPA at least seven days prior to work beginning.
Discharge is authorized when the application status is listed as "authorized"
in the EPA public NOI database or when the APPLICANT receives an EPA
authorization letter by mail.