Stormwater Management & Erosion Control Local Law
Performance Standards

Erosion Control Plans shall be prepared in accordance with performance standards which have been structured to achieve the purposes and objectives of a Stormwater Management & Erosion Control Local Law as well as to ensure that the quality and quantity of runoff after development is not substantially altered from pre-development conditions.   The following performance standards must be satisfied:

1. Existing vegetation on a project site shall be retained and protected as much as possible to minimize soil loss from the project site.

2. Sediment control practices/measures, where necessary, shall be designed to protect the natural character of waterbodies on-site as well as off-site. The practices must be in place from the start of land disturbance activities to establishment of permanent stabilization.

  1. The off-site impacts of erosion and sedimentation from the development site shall not be any greater during and following land disturbance activities than under pre-development conditions.
  2. Water in stream reaches on-site and downstream of construction areas shall not have substantial visible contrast relative to color, taste, odor, turbidity and sediment deposition from the water in reaches upstream of the construction area.
  3. Sediment laden runoff shall not be allowed to enter any waterbody and result in deposition on the bottom of the waterbody, degrade its natural biological functions, or be deleterious to the classified usage of the water.

3. Erosion and sediment control measures shall be constructed prior to beginning any land disturbances. All runoff from disturbed areas shall be directed to the sediment control devices. These devices shall not be removed until the disturbed land areas are stabilized.

4. Specific guidance.

  1. Exposure Restrictions: No more than 10 acres of unprotected soil shall be exposed at any one time. Previous earthwork shall be stabilized in accord with approved design standards and specifications referenced in Section 4.h before additional area is exposed.
  2. Grading: Perimeter grading shall blend with adjoining properties.
  3. Vegetative Protection: Where protection of trees and/or other vegetation is required, the location shall be shown on a Erosion Control Plan or on the drawings for the proposed development project. The method of protecting vegetation during construction shall conform to the design specifications referenced in Section 4.h.
  4. Drainage Control.

1) Surface runoff that is relatively clean and sediment free shall be diverted or otherwise prevented from flowing through areas of construction activity on the project site. This will greatly reduce sediment loading in surface runoff.

2) A fill associated with an approved temporary sediment control structure or permanent stormwater management structure, shall not be created which causes water to pond off-site on adjacent property, without first having obtained ownership or permanent easement for such use from the owner of the off-site or adjacent property.

3) In general, natural drainage channels shall not be altered. Pursuant to Article 15 of the Environmental Conservation Law, a protected stream and banks thereof shall not be altered or relocated without the approval of the Department of Environmental Conservation.

4) Runoff from any land disturbing activity shall not be discharged or have the potential to be discharged off-site or into storm drains or into water courses unless such discharge is directed through a properly designed, installed and maintained structure, such as a sediment trap, to retain sediment on-site. Accumulated sediment shall be removed when it takes up 60% of the storage capacity of the sediment retention structure. (See Section 4.h below for design specifications.)

5) For finished grading, adequate gradients shall be provided so as to prevent water from standing on the surface of lawns for more than 24 hours after the end of a rainfall, except in a swale flow area which may drain as long as 48 hours after the end of rainfall.

6) Permanent swales or other points of concentrated water flow shall be stabilized. Biotechnical approaches using certain types of grasses, such as reed canary grass, are preferable to using sod, gabions and rip-rap where water quality enhancement is a high priority and the swale design allows. However, sod, gabions, or rip-rap may be used to stabilize swales where soils and gradient preclude the use of reed canary grass. Use of grasses may require an erosion control matting as provided for in the design specifications referenced in Section 4.h below.

7) Surface lows over cut and fill slopes shall be controlled as provided for in the design specifications for vegetating waterways referenced in Section 4.h.

  1. Timing.

    1) Except as noted below, all sites shall be seeded and mulched with erosion control materials such as rye grass, straw mulch, jute, or excelsior (wood shavings) within 15 days of initial disturbance. If construction has been suspended, or sections completed, areas shall be seeded immediately and stabilized with erosion control materials. Maintenance shall be performed as necessary to ensure continued stabilization.

    2) For active construction areas, such as borrow or stockpile areas, roadway improvements, and areas within 50 feet of a building under construction, a perimeter sediment control system consisting, for example, of silt fencing or hay bales, shall be installed and maintained to contain soil.

    3) On cut sides of roads, ditches shall be stabilized immediately with rock rip-rap or other non-erodible liners, or where appropriate, vegetative measures such as sod. When seeding is approved, an anchor mulch shall be used and soil shall be limed and fertilized in accord with recommendations referenced in Section 4.h.

    4) Permanent seeding shall optimally be undertaken in the spring from April 1 through June 15, and in late summer from August 1 to October 15. During the peak summer months and in the fall after October 15 when seeding is found to be impracticable, an appropriate mulch shall be applied. Permanent seeding may be undertaken during summer if plans provide for adequate watering of the seedbed.

      Option 4A: Ground cover can be required as stated in the above sub-section during the winter months;

      Option 4B: Stricter requirements for ground cover and erosion control for late autumn - early spring construction can be put in place to make it more difficult to build in the non-growing season;

      Option 4C: A moratorium for construction in the winter months could be established.

    5) All slopes steeper than 15%, as well as basin or trap embankments, and perimeter dikes shall, upon completion, be stabilized with sod, seed and anchored straw mulch, or other approved stabilization measures. Areas outside of the perimeter sediment control system shall not be disturbed. Maintenance shall be performed as necessary to ensure continued stabilization.

    6) Temporary sediment trapping devices shall be removed within thirty (30) calendar days following establishment of permanent stabilization in all contributory drainage areas. Stormwater management structures used temporarily for sediment control shall be made permanent within this time period as well. Accumulated sediments removed from temporary sediment traps or permanent stormwater management facilities shall be disposed of such that they will not erode and enter a waterbody.

  2. Stream Corridor Management. The bed and banks of all on-site and off-site streams which may be impacted by land clearing, grading, and construction activities shall be protected to prevent sedimentation, stream bank erosion, stream enlargement, or degradation of loss of fisheries habitat. Measures for protecting the bed and/or banks of a stream may include gabion baskets, rip-rap, log cribbing, and vegetative measures. Whenever possible, vegetative stream bank stabilization practices are recommended over structural practices such as rip-rap and gabion linings that may unnecessarily alter the existing stream ecosystem. Native species of vegetation shall be used for stream bank stabilization wherever practical. In undertaking stream bank stabilization activities for protected streams, the Applicant shall comply with appropriate protection of water provisions in Article 15 of the Environmental Conservation Law.
  3. Maintenance

    7) All points of construction ingress and egress shall be protected to prevent the deposition of materials onto traversed public thoroughfares either by installing and maintaining a stabilized construction entrance or by maintaining a vehicle wash area in a safe disposal area to wash vehicle shells and undercarriage. All materials deposited onto public thoroughfares shall be removed immediately. Proper precaution shall be taken to assure that the removal of materials deposited onto public thoroughfares will not enter catch basins, storm sewers, or waterbodies.

    8) Accumulated sediment shall be removed when 60% of the storage capacity of sediment retention structures is reached. All removed sediment shall be disposed of in a spoil area where it can be graded, mulched and seeded to prevent erosion and sedimentation.

  4. Design specifications. The designs, standards and specifications for controlling erosion and sedimentation found in the most recent version of the following publication are acceptable for use and shall be identified and shown in the Erosion Control Plan: ANew York Guidelines for Urban Erosion and Sediment Control, Urban Soil Erosion and Sediment Control Committee.
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CLW IO 2004