In addition to the information required by Section 7.1 or otherwise by the Planning Board (and to the extent not already included therein), the Stormwater Management Plan shall also include, address, undertake, acknowledge and/or discuss the following, as applicable:
Controls and mechanisms to be implemented, together with any other strategies or BMPs that will enhance Sedimentation and/or Filtration and limit erosion, with particular attention to any discharge into the MS4;
Designs to optimize Contaminant removal efficiencies based on standards and performance data published by the UNH Stormwater Center and/or included in the latest version of the NH Stormwater Manual; and
Minimal use of identified deicing chemicals and salt, consistent with any other requirements applicable to Critical Areas; and
Salt storage and drainage controls in accordance with NH DES published guidance and, if applicable, MS4 permit requirements, including tracking and reporting salt usage using the salt accounting system administered by the UNH Technology Transfer Center [https://sso.roadsalt.unh.edu/];
Controls to be regularly inspected per the schedule established, but during the Construction Phase, not less frequently than bi-weekly, and within 24 hours after a rainstorm of 0.25 inches in a 24-hour period or greater at any time during or after construction;
Identified deficiencies to be corrected within 48 hours (or, if the public health or welfare may be endangered, within 24 hours), with records thereof retained on-site; and
Updates as necessary, with changes subject to Stormwater Manager approval before implementation;
Drainage Reports
Drainage analysis, including calculations showing volume, Peak Flow and velocity of present and future Stormwater Runoff, as well as a comparison of existing and post-construction estimated Peak Flow at each outlet location for 50-year and 100- year frequency 24-hour storm events, and for rainstorms of one inch in a 24-hour period;
As applicable, an off-site drainage plan (which may be part of the existing conditions discussion), special reports, studies and maintenance information relating thereto;
For subdivisions comprising lots with frontage on existing private or public roadways, additional discussion of Stormwater Management for Stormwater Runoff from the new lots discharging to the roadside Drainage System;
Both temporary and permanent soil stabilization measures in accordance with the NHDES Stormwater Manual Volume 3;
Upon completion of construction, the site shall be stabilized, temporary measures shall be removed, and affected areas shall be restored, as confirmed in the final inspection contemplated by Section 5.6;
Impact of Construction Activities on (a) existing topography, (b) drainage patterns, (c) soils, (d) ground cover, I Critical Areas, (f) upstream areas draining through the site, (g) adjacent development, (h) existing stormwater facilities, (i) on- and off-site utilities, (j) surface water and (k) other pertinent features;
Minimize Impervious Surfaces for parking areas and roads to the extent practicable;
Stormwater Runoff from new Impervious Surfaces to be directed to a subsurface Stormwater Treatment mechanism or discharged to a naturally occurring or fully replanted and vegetated area with slopes of 15 percent or less and with adequate controls to prevent soil erosion and concentrated flow; and
Stormwater Runoff from all Impervious Surfaces shall be treated to remove at least 90% of Total Suspended Solids and at least 60% of both total nitrogen and total phosphorus, as specified in the NH Stormwater Manual, Volumes 1 and 2, December 2008, as amended, or by another equivalent source;
Facilitate post-construction Infiltration to maximize the groundwaterrecharge volume in accordance with NHDES Alteration of Terrain requirements and applicable BMPs;
Landscaping
Stormwater Treatment areas to be planted with vegetation appropriate for the site conditions: trees, grasses, shrubs and/or other plants in sufficient numbers and density to prevent erosion and to facilitate Infiltration; and
Existing site vegetation to be retained, protected, restored and/or supplemented;
Miscellaneous
Stump removal and disposal;
Describe the tributary area (include at least one-quarter (1⁄4) mile downstream), drainage channels, conveyance systems and downstream receiving waters; and
Appendices (copies of tables, graphs, charts, test pit, percolation test and other data and assumptions used in any required calculations).
7.3Updates; Alterations.
The SMP shall be updated, if necessary, during the Construction Phase and the revisions submitted to the Planning Board and the Stormwater Manager for approval. No SMS structure or feature shall be altered without the prior approval of the Planning Board in consultation with the Stormwater Manager and other Town officials, as appropriate. The costs of any alteration, or professional review, repair or restoration of any structure or feature altered in violation of this Section, shall be borne, jointly and severally, by the Responsible Parties.
7.4Annual Certification.
By September 1 of each calendar year, an engineer licensed by the State of New Hampshire representing the Responsible Parties shall file with the Stormwater Manager an annual report:
Identifying any necessary repairs (other than routine maintenance) to any component of the SMS during the prior year and confirming their completion, or the scheduled date thereof; and
If the SMS or any component thereof is not functioning per the SMP, the nature of the malfunction or deficiency, what action will be taken to address the malfunction or deficiency, and when it will be completed; and
If the report is not filed by September 1, the Stormwater Manager, together with any professional consultants the Stormwater Manager may determine, may access the site, at a time agreed with the Responsible Parties and at their expense, to determine compliance with these regulations.
