Town of Wilton, NH

Stormwater Management Regulations

3.0 Definitions

For the purposes of these regulations, the following terms have the meanings set forth below, whether or not they are capitalized herein. To the extent they are not defined below, terms used herein have the meanings set forth in the Zoning Ordinance. Unless otherwise noted, references to Sections in these regulations are to the sections of these regulations.

3.0.1 Best Management Practices (BMPs).

Recommendations for proven measures or approaches to Stormwater Management or the conduct of Construction Activities or other land use activities, the application of which will accomplish the Stormwater Management Goals and which have been adopted or approved by an entity or body having jurisdiction over, or expertise in, the subject, as they may from time to time be amended or modified, including, without limitation, Forestry Control BMPs, Homeowner’s BMPs and any applicable construction, agricultural or other BMPs issued from time to time, as well as other guidance published by NHDES.

3.0.2 Bioretention System.

A system (sometimes referred to as a rain garden) using conditioned plantings, soil beds, gravel beds and/or vegetation in shallow depressions to collect and filter moderate amounts of stormwater runoff to maintain or improve its quality.

3.0.3 Building Inspector.

The Wilton Building Inspector.

3.0.4 Catch Basin.

An engineered drainage structure typically designed to collect stormwater runoff from impervious surfaces such as driveways, roads and parking areas, and convey it to local waterways through a Drainage System.

3.0.5 Construction Activities.

The demolition, construction or reconstruction of structures, roads, trails, driveways, parking areas, bridges, Drainage Systems, etc., on sites, public or private, located in Wilton, and all activity preparatory or incidental to such construction, including, without limitation, clearing, excavation, grading, filling, soil compaction, stockpiling topsoil, and any other activity that disturbs or alters the terrain.

3.0.6 Construction Phase.

The period during which Construction Activity takes place.

3.0.7 Contaminants.

Organic or inorganic (1) particulate material, including, without limitation, soil, sand, minerals, solid waste, petroleum products, biological material and chemical waste, or (2) gas, in each case, dissolved or suspended in Stormwater Runoff, whether or not the material itself could have a harmful effect on persons, property, its use, or the environment.

3.0.8 Covered Construction Activity.

Construction Activity described in Section 5.1 and not exempt under Section 5.2.

3.0.9 Critical Area.

An area (1) within fifty (50) feet of any wetland; (2) exceeding two thousand (2,000) contiguous square feet in highly erodible soils; (3) within, or within applicable buffers or setbacks prescribed by, the Watershed or Aquifer Protection Districts of the Town of Wilton or its MS4 Area, or (4) containing a slope greater than 10% in any horizontal segment of 25 feet.

3.0.10 Culvert.

A drainage structure designed to convey surface water or Stormwater Runoff beneath a driveway, road, embankment or other similar structure.

3.0.11 Detention.

Temporary storage of Stormwater Runoff, in a structure with a defined outlet or otherwise, before its Infiltration at a controlled rate, primarily to reduce the intensity of peak flows during storm events.

3.0.12 Disturb (including disturbed).

Action that alters the terrain, existing vegetation and/or the soil on a site, including, without limitation, Construction Activities.

3.0.13 Disturbed Area.

The total area of a site that has been, or will be, disturbed by Construction Activity.

3.0.14 Drainage System.

A public or private network of structures, including, without limitation, culverts, swales, ditches, channels and/or underground pipes (or a single such structure) designed to transport Stormwater Runoff either onsite or offsite to control its quantity, quality, timing and/or distribution.

3.0.15 Erosion.

The removal of soil, sand or rock fragments by action of water, wind, ice, gravity or other natural processes.

3.0.16 Filtration.

The process of removing Contaminants from Stormwater Runoff by passing it through a filtering medium such as sand, organic material, fabric or soil, or by sedimentation or by chemical means.

3.0.17 Forestry Control BMPs.

Best Management Practices for Erosion Control on Timber Harvesting Operations, issued by The New Hampshire Division of Forests and Lands and The UNH Cooperative Extension, 2016, as it may from time to time be amended or modified.

3.0.18 Groundwater.

Water located in zones beneath the land surface, including, without limitation, aquifers and seepage.

3.0.19 Homeowner’s BMPs.

The Best Management Practices contained in the New Hampshire Homeowners’ Guide to Stormwater Management, issued by The Watershed Management Bureau of the New Hampshire Department of Environmental Services, November 2019, as it may from time to time be amended or modified.

3.0.20 Illicit Discharge Detection and Elimination (IDDE).

The Illicit Discharge Detection and Elimination ordinance adopted by the Town of Wilton, as it may from time to time be amended or modified.

3.0.21 Impervious Surface.

Any manmade surface that prevents or significantly impedes Infiltration, including, without limitation, structures, rooftops, artificial turf, paved roads, driveways, parking areas and trails (or those constructed with compacted soil or gravel) and other outdoor areas to the extent constructed with non-porous materials.

3.0.22 Infiltration.

The process by which Stormwater Runoff percolates into the ground.

3.0.23 Low Impact Development (LID).

Strategies that maintain or replicate preexisting Stormwater Runoff and Infiltration characteristics, including, without limitation, site planning, use of pervious materials, Bioretention Systems, green roofs, detention areas, non-engineered Drainage Systems and other functionally similar BMPs located near the source of Stormwater Runoff.

3.0.24 Municipal Separate Storm Sewer System (MS4).

The Municipal Separate Storm Sewer System of the Town of Wilton.

3.0.25 MS4 Area.

The urbanized area of the Town of Wilton covered by the MS4 Permit issued to the Town by the U.S. Environmental Protection Agency (EPA), as such area may from time to time be modified.

3.0.26 Maintenance Agreement.

The agreement, in recordable form and approved by the Planning Board, addressing, among other things, continuous maintenance of the Stormwater Management System(s) on a property or properties and other agreements and obligations with respect to the applicable Stormwater Management Plan, as further described in Section 10.0.

3.0.27 Outlet Location.

The point at which water discharges from a pipe weir, swale, ditch or drain.

3.0.28 Peak Flow.

The maximum flow of water leaving a disturbed area due to a storm event, expressed in CFS (cubic feet per second), based on the 100-year frequency 24- hour storm discharge rate (as that standard may be increased from time to time by applicable law or regulation).

3.0.29 Planning Board.

The Wilton Planning Board.

3.0.30 Post-Construction Phase.

The period following completion of Construction Activities.

3.0.31 Precipitation.

Any product of the condensation of atmospheric water vapor that falls under gravity from clouds, including, without limitation, drizzle, rain, sleet, snow, ice pellets, graupel and hail.

3.0.32 Recharge.

Replenishment of groundwater and surface waters via Infiltration, maintaining water flow and preserving water table levels.

3.0.33 Redevelopment.

Any Construction Activity proposed for land on which Impervious Surfaces constitute, or will, after such Construction Activity, constitute, more than 60% of its area.

3.0.34 Restoration (including restore).

Returning an area to a close approximation of its ecological, hydrological and topographical condition prior to disturbance.

3.0.35 Responsible Party(ies).

The owner(s) and/or operator(s) of the property or the facility where Construction Activities will take, or have taken, place, and/or any other individual(s) or entity identified in the Maintenance Agreement.

3.0.36 Retention.

Temporary storage of Stormwater Runoff in a structure without a defined outlet and whose only outlet is Infiltration.

3.0.37 Sedimentation.

The process by which solid Contaminants are removed from Stormwater Runoff by settling in a Bioretention System or other detention structure.

3.0.38 Select Board.

The Wilton Select Board.

3.0.39 Stabilized.

The state of a site when soils there will not experience accelerated or unnatural erosion. In addition to any other requirements established by the Planning Board or the Stormwater Manager, areas without Impervious Surface are presumed to be stabilized when a minimum of 85% vegetative cover has been established, a minimum of 3" of non-erosive material such as stone or a certified compost blanket has been installed, or erosion control blankets have been installed. Areas with Impervious Surface are presumed to be stabilized when base course gravels have been installed.

3.0.40 Stormwater Application.

The application required by Section 5.3, including all of the information set forth in Section 6.0.

3.0.41 Stormwater Management.

The use of, among other things, site design, construction, structural and operational BMPs, and other strategies designed to achieve Stormwater Management Goals in connection with Construction Activities.

3.0.42 Stormwater Management Goals.

During each phase of Construction Activity (including the Post-Construction Phase): (1) minimize on- and offsite erosion; (2) reduce Peak Flow; (3) maintain predevelopment, or pre-existing, Stormwater Runoff volume and patterns; (4) prevent contamination of Stormwater Runoff and degradation of its quality; (5) maximize Infiltration, (6) maximize groundwater recharge; (7) to the extent practical, capture and reuse stormwater runoff; (8) preserve existing vegetation and (9) protect any Critical Areas that may be affected.

3.0.43 Stormwater Management Plan (SMP).

The document approved by the Planning Board as part of a Stormwater Application and incorporated by reference in the Maintenance Agreement, setting out the means by which Stormwater Management will be implemented, the Stormwater Management Goals achieved, and containing the information and undertakings set forth in Section 7.0.

3.0.44 Stormwater Management System (SMS).

The system of mechanisms, structures, tools and/or controls, including, without limitation and where appropriate, Drainage Systems, Bioretention Systems, Catch Basins, Low Impact Development strategies, Stormwater Treatment mechanisms, Filtration mechanisms, and their respective components, that implements either (1) Stormwater Management, including Best Management Practices in connection with any Construction Activity, or (2) a required Stormwater Management Plan.

3.0.45 Stormwater Manager.

The individual or individuals designated from time to time by the Select Board or its designee to administer, enforce and monitor compliance with these regulations and the town’s MS4 Permit.

3.0.46 Stormwater Runoff.

The water from precipitation, drainage or other surface runoff, including, without limitation, snowmelt, that is not absorbed, evaporated, or otherwise stored within the contributing area.

3.0.47 Stormwater Treatment.

The process of removing Contaminants from Stormwater Runoff to improve its quality, by Sedimentation, Filtration, Subsurface Gravel Wetlands, or otherwise.

3.0.48 Surface Gravel Wetland.

A Low Impact Development system to treat Nonpoint Source Pollution combining Sedimentation structures with chemical Filtration, such as microbial nitrogen removal in an anaerobic subsurface zone.

3.0.49 Surface Water.

Water bodies or wet areas located on top of the Earth’s surface, including, without limitation, streams, rivers, ponds, lakes, wetlands and vernal pools (seasonal, intermittent or otherwise).

3.0.50 Swale.

A shallow, low-gradient, vegetated (grass, plants and/or shrubs) drainage channel designed to convey and treat shallow, redirected Stormwater Runoff and facilitate Infiltration.

3.0.51 Total Suspended Solids (TSS).

The dry weight of suspended particles greater than or equal to 2 microns in size, usually expressed as grams/liter.

3.0.52 Watershed.

The area of land from which surface water and/or groundwater drains to a waterbody.

3.0.53 Zoning Ordinance.

Section A, Zoning Ordinance, of the Wilton Land Use Laws and Regulations, as it may from time to time be amended or modified.