Sites for all land development activities disturbing more than 1/2 acre must be stabilized by means of mulch, vegetation, or equivalent as soon as practicable, and within no more than seven days, whenever construction activities have temporarily or permanently ceased at that site, unless earth-disturbing activities will be resumed within 14 days. In the case of snow cover or frozen ground, sites should still be mulched, to control runoff during snowmelt. Maintenance should be performed as necessary to ensure continued stabilization. Specifications for mulching as well as temporary and permanent vegetative stabilization can be found in the New York Standards and Specifications for Erosion and Sediment Control. In addition, land-disturbing activities that are subject to a basic or full SWPPP shall be required to comply with any standards contained therein.
Land development activities disturbing less than 1/2 acre may use Appendix E of the New York Standards and Specifications for Erosion and Sediment Control, called "Erosion and Sediment Control Plan for Small Homesite Control," to meet the SWPPP requirement, unless the Stormwater Management Officer requests more detail. In addition, land-disturbing activities that are subject to a basic or full SWPPP shall be required to comply with any standards contained therein.
Vegetation planted for the purpose of site stabilization and/or stormwater management should not include species that are considered "invasive." Applicants must avoid plants on lists through qualified sources such as the Invasive Plant Council of New York State, as well as the Tompkins County Invasive Plant List. Applicants should refer to Table H.5 of the New York State Stormwater Management Design Manual for a list of plants native to New York State which are recommended for stormwater ponds, wetlands, bioretention, and other vegetated treatment areas.
Projects should follow the guidance on winter site stabilization/site inspections posted by DEC, and those projects requiring a Full SWPPP should make use of the water quality sizing guidelines for cold climates in Appendix I of the New York State Stormwater Management Design Manual, because the City meets the "rule of thumb" of having average annual snowfall depth that is greater than average annual precipitation depth.
Redevelopment projects and high-density projects (in areas zoned for high density) often make more efficient use of the land, and may reduce overall impacts to natural areas. This regulation is not intended to create a disincentive for such projects. The Stormwater Management Officer can allow some degree of flexibility for such projects, so long as the minimum New York State standards are met. Chapter 9 of the New York State Stormwater Management Design Manual (currently a draft) should be followed for redevelopment projects.
Land development activities shall not discharge untreated stormwater directly into a jurisdictional wetland or natural water body without adequate treatment, nor modify jurisdictional wetlands for stormwater impoundment. Silt fence shall not be placed within 50 feet of a wetland boundary.
The City of Ithaca notes that Chapter 7 of the Stormwater Design Manual provides helpful charts and criteria to guide selection of appropriate stormwater management practices for a site. Applicants should consider these criteria while selecting practices.
If a project is composed of separate and distinct phases, the stormwater management practices may also be installed in phases, but the standards of this regulation must be met during all phases.
Off-site stormwater control areas may be shared between two or more property owners or developments, provided that the Stormwater Management Officer has approved the design and the required maintenance agreements, and the required easements have been obtained and recorded.
To the maximum extent practicable, stormwater management objectives shall be met by incorporating nonstructural stormwater management strategies into the project design. Nonstructural practices reduce the need for expensive and high-maintenance stormwater management facilities, and thereby are a benefit to the applicant and to the City of Ithaca. The following nonstructural strategies should be applied wherever possible:
Protect areas that provide water quality benefits or areas particularly susceptible to erosion and sediment loss.
Maximize the protection of natural drainage features and vegetation.
Minimize land disturbance including clearing and grading.
Minimize impervious surfaces and break up or disconnect the flow of runoff over impervious surfaces.
Maximize the time of concentration from preconstruction to post-construction. "Time of concentration" is defined as the time required for water to flow from the most remote point of the site area (in time of flow) to the outlet.
Favor movement of water through the site as sheet flow through vegetated areas, rather than concentrated flows.
Provide vegetated open-channel conveyance systems discharging into and through stable vegetated areas.
Provide low-maintenance landscaping that encourages retention and planting of native vegetation and minimizes the use of fertilizers and pesticides.
Provide other source controls to prevent or minimize the use or exposure of pollutants at the site, in order to prevent or minimize the release of those pollutants into stormwater runoff.
DEC has identified a set of 18 "better site design practices" which can reduce the impacts of a project, and also often reduce costs. Many of these practices will result in smaller required stormwater treatment and storage volumes. These are generally nonstructural or smaller-scale practices than those described in the Stormwater Design Manual. Recommended better site design practices are described in the DEC document called "Better Site Design."
If the applicant contends that the minimum number of practices cannot be incorporated into project design due to site limitations, the applicant shall explain such limitations. If the limitations are due to conflict with other City of Ithaca regulations, the Stormwater Management Officer will work with the applicant to the extent possible.
The DEC has also identified a set of six practices (several of which overlap with the better site design practices above) which qualify for stormwater credits. If these practices are implemented as described in the document titled "The Use and Implementation of Stormwater Credits," they can result in a calculated reduction in the water quality treatment volume, and occasionally in the water quantity storage volumes, required for projects subject to a full SWPPP.
These practices must be implemented as described in "The Use and Implementation of Stormwater Credits."
These practices must be reviewed and approved by the City of Ithaca before the credit can be taken.
DEC's procedure for application of these credits is currently evolving. Projects making use of credits may require a sixty-day review by DEC and/or a letter from the City of Ithaca certifying that the credit has been applied correctly.
Applicants should make use of these credits wherever site conditions permit.
Any nonstructural strategy applied that requires continued protection or maintenance in order to function over the long term should include an appropriate written agreement to ensure such protection or maintenance, either by means of an easement, maintenance agreement, deed restriction, or dedication to an appropriate government agency or land trust, as approved by the reviewing board.
The following applies to projects requiring a full SWPPP. In order to maximize groundwater recharge and reduce runoff, infiltration practices should be used where site conditions permit. If more than 50% of the soil at a project site is shown as hydrologic group A or B in the county soil survey, the applicant must do one of the following:
Conduct a preliminary screening to determine whether the site meets the criteria for infiltration practices. The preliminary screening involves checking the most detailed current NRCS soil survey (available in paper form, by contacting the local Soil and Water Conservation District office) to determine whether the infiltration practice criteria described in the Stormwater Design Manual are met. If the soil characteristics show that the criteria are likely to be met, the applicant must continue feasibility testing as described in Appendix D of the Stormwater Design Manual, and move forward with an infiltration practice if the site passes both initial feasibility and concept design testing. If at any point infiltration is determined infeasible, proceed to Option 2 (Subsection B) below.
Apply a combination of site appropriate better site design practices and/or stormwater credits that will result in sufficient infiltration of stormwater runoff, as approved by the Stormwater Management Officer.
However, stormwater from high pollutant loading areas or stormwater hotspots or industrial stormwater exposed to source material shall not be infiltrated.