City of Northwoods, MO Design Requirements

[Ord. No. 07-02 §1, 5-8-2007]

Design. The design of erosion and sediment controls required for land disturbance activities shall comply with the following minimum requirements:

Land disturbance, erosion and sediment control practices and watercourse crossings shall be adequate to prevent transportation of sediment from the site.

Materials brought to any site or property under a permit issued under this code, where said material is intended to be utilized as fill material at the site for land disturbance, erosion or sediment control, shall consist of clean uncontaminated earth, soil, dirt, sand, rocks, gravel or masonry materials or other approved materials.

Cut and fill slopes shall be no greater than 3:1 except as approved by the Department of Public Works to meet other community or environmental objectives. All exactions, grading or filling shall have a finished grade not to exceed a 3:1 slope (thirty-three percent (33%)). Steeper grades may be approved by the Director of Public Works if the excavation is through rock or if the excavation or the fill is adequately protected (a designed heal wall or toe wall may be required). Turf reinforce mattresses (TRM), rock slopes and other Best Management Practices (BMP) could be utilized for slopes in excess of 3:1, but should be approved by a qualified geotechnical engineer hired by the developer and approved by the City prior to and/or during installation and they should be listed for concurrence prior to installation. Retaining walls that exceed a height of forty-two (42) inches shall require the construction of safety guards as identified in the appropriate Sections(s) of the adopted BOCA Codes and must be approved by the City Building Department. Permanent safety guards shall be constructed in accordance with the appropriate Section(s) of the adopted BOCA Codes (latest edition). Also, the following water quality issues as a reference can be used: Protecting Water Quality — A Field Guide to Erosion, Sediment and Stormwater Best Management Practices for Development Sites in Missouri.

Clearing and grading of natural resources, such as forests and wetlands, shall not be permitted, except when in compliance with all other City ordinances.

Clearing techniques that retain existing vegetation to the maximum extent practicable shall be used and the time period for disturbed areas to be without vegetative cover shall be minimized to the extent practical.

Clearing, except that necessary to establish sediment control devices, shall not begin until all sediment control devices have been installed and have been stabilized.

Phasing shall be required on all sites disturbing greater than thirty (30) acres of land. The size of each phase will be established by the Department of Public Works at the time of plan review for the issuance of a major land disturbance permit. Phasing should identify the expected date on which clearing will begin, the estimated duration of exposure of cleared areas and the sequence of clearing, installation of temporary sediment control measures, installation of storm drainage, paving streets and parking areas and establishment of temporary and permanent vegetative cover. The Director of Public Works may waive specific requirements for the content of submissions upon finding that the information submitted is sufficient to show that the work will comply with the objective and principles of these regulations.

Erosion Control Design. Erosion control requirements shall include the following:

Soil stabilization shall be completed within five (5) days of clearing or inactivity in construction.

If seeding or another vegetative erosion control method is used, it shall become established within two (2) weeks or the site shall be reseeded or a non-vegetative option employed. Where natural vegetation is removed during grading, vegetation shall be re-established in such a density, seventy-five percent (75%) vegetative cover of area disturbed, as to prevent erosion. Permanent type grasses shall be established as soon as possible or during the next seeding period after grading has been completed. When grading operations are completed or suspended more than thirty (30) days, permanent grass must be established at sufficient density, fifty percent (50%) to seventy-five percent (75%) vegetative cover, to provide erosion control on the site. Between permanent grass seeding periods, temporary cover shall be provided according to the Director of Public Works recommendations. All finished grades (areas not to be disturbed by future improvements) in excess of twenty percent (20%) slopes 5:1 shall be mulched and tacked.

Techniques shall be employed to ensure stabilization on steep slopes and in drainage ways. Provisions shall be made to accommodate the increased runoff caused by changed soil and surface conditions during and after grading. Unvegetated open channels shall be designed so that gradients result in velocities of two (2) fps (feet per second) or less. Open channels with velocities more than two (2) fps and less than five (5) fps shall be established in permanent vegetation by use of commercial erosion control blankets or lined with rock riprap or concrete or other suitable materials as approved by the Director of Public Works. Detention basins, diversions or other appropriate structures shall be constructed to prevent velocities above five (5) fps.

Soil stockpiles must be stabilized or covered at the end of each workday or perimeter controls must be in place to prevent silt from the stockpile from leaving the site.

The entire site must be stabilized, using a heavy mulch layer or another method that does not require germination to control erosion, at the close of the construction season.

Techniques shall be employed to prevent the blowing of dust or sediment from the site.

Techniques shall be employed to divert upland runoff past disturbed slopes. The adjoining ground to development sites (lots) shall be provided with protection from accelerated and increased surface water, silt from erosion and any other consequences of erosion. Runoff water from developed areas (parking lots, paved sites and buildings) above the area to be developed shall be directed to diversions, detention basins, concrete gutters and/or underground outlet systems. Sufficiently anchored straw bales may be temporarily substituted with the approval of the Director of Public Works. All lots shall be seeded and mulched or sodded before an occupancy permit shall be issued except that a temporary occupancy permit may be issued by the Building Department in cases of undue hardship because of unfavorable ground conditions.

Sediment Control Design. Sediment control requirements shall include:

Settling basins, sediment traps or tanks and perimeter controls.

Settling basins shall be provided for each drainage area within ten (10) or more acres disturbed at one time and shall be sized to contain one-half (0.5) inch of sediment from the drainage area and be able to contain a 2-year, twenty-four (24) hour storm. If the provision of a basin of this size is impractical, other similarly effective Best Management Practices (BMP), as evaluated and specified in the Storm Water Pollution Prevention Plan (SWPPP), shall be provided.

Settling basins shall be designed in a manner that allows adaptation to provide long-term stormwater management as required by the department(s) having enforcement authority and responsibilities described in this code.

Settling basins shall have stabilized spillways to minimize the potential for erosion of the spillway or basin embankment.

Protection for adjacent properties by the use of a vegetated buffer strip in combination with perimeter controls.

Watercourse Design. Watercourse protection requirements shall include:

Encroachment into or crossings of active watercourses/riparian areas and wetlands shall be avoided to the maximum extent practicable. All County, State and Federal permits and approvals shall be obtained by a permit holder prior to beginning work authorized by a land disturbance permit.

Development along natural watercourses shall have residential lot lines, commercial or industrial improvements, parking areas or driveways set back a minimum of twenty-five (25) feet from the top of the existing stream bank. The watercourse shall be maintained and made the responsibility of the subdivision trustees or, in the case of a site plan, by the property owner. Permanent vegetation shall be left intact. Variances will include designed stream bank erosion control measures and shall be approved by the Director of Public Works. FEMA and U.S. Army Corps of Engineers guidelines shall be followed where applicable regarding site development areas designated as floodplains and wetlands.

Stabilization of any watercourse channels before, during and after any in-channel work.

If a defined watercourse is to be realigned or reconfigured, clearing and grubbing activities within fifty (50) feet of the watercourse shall not begin until all materials and equipment necessary to protect the watercourse and complete the work are on site. Once started, work shall be completed as soon as possible. Areas within fifty (50) feet of the watercourse shall be recontoured and revegetated, seeded or otherwise protected within five (5) working days after land disturbance activities have ceased.

All stormwater conveyances shall be designed according to the criteria of the St. Louis Metropolitan Sewer District (MSD) and the necessary MSD permits obtained.

Stabilization adequate to prevent erosion shall be provided at the cutlets of all pipes and paved channels.

Construction Site Access Design. Construction site access requirements for major land disturbance activities shall include:

A temporary access road provided at all land disturbance sites including a wash-down area supporting all active sites.

The Department of Pubic Works may require other measures to ensure that construction vehicles do not track sediment onto public streets or be washed with wash effluent channeled directly into storm drains.

Control Of Construction Materials And Waste. Control requirements for construction materials, construction wastes and other wastes generated on site at land disturbance sites shall include provisions satisfactory to the City.

Spill prevention and control facilities for materials such as paint, solvents, petroleum products, chemicals, toxic or hazardous substances, substances regulated under the Resource Conservation and Recovery Act (RCRA) or the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) and any wastes generated from the use of such materials and substances, including their containers. Any containment systems employed to meet this requirement shall be constructed of materials compatible with the substances contained and shall be adequate to protect both surface and ground water.

Collection and disposal of discarded building materials and other construction site wastes, including those listed in Subsection (F)(1) above.

Litter control.

Control of concrete truck washouts.

Assurance that on-site fueling facilities will adhere to applicable Federal and State regulations concerning storage and dispensers.

Provision of sufficient temporary toilet facilities to serve the number of workers on major land disturbance sites.