1070 (09/05)
Wisconsin Department of Natural Resources
Conservation Practice Standard
Note: Words in the standard that are shown in italics are described in X. Definitions. The words are italicized the first time they are used.
I. Definition
A temporary permeable fabric installed in a waterway or waterbody to minimize sediment transport. A silt curtain does not extend to the bottom of the channel and is placed parallel or perpendicular to the direction of flow.
II. Purposes
The purpose of this practice is to provide sediment containment while construction activities are occurring in or directly adjacent to a waterway or waterbody.
III. Conditions Where Practice Applies
This practice applies where construction activities intrude or are directly adjacent to a waterway or waterbody. This includes but is not limited to bridge construction, rip rap placement, utility work, streambank restoration, boat launches and dredging.
Silt curtain is intended for calm water conditions where it will not be subjected to wind, wave, or current. Silt curtains are appropriate to settle out coarse and granular soils where water depth at the time of construction is greater than or equal to 4 feet. For applications in finer sediment or moving water see WDNR Technical Standard 1069 Turbidity Barrier.
IV. Federal, State, and Local Laws
Users of this standard shall be aware of applicable federal, state, and local laws, rules, regulations, or permit requirements governing the use and placement of silt curtains. This standard does not contain the text of federal, state, or local laws.
V. Criteria
This section establishes the minimum standards for design, installation and performance requirements.
A. Installation – Details of construction not listed in the text shall conform to the pertinent requirements of Figure 1.
1. The silt curtain shall be installed before construction activities are initiated in or adjacent to the waterway or waterbody. Install the silt curtain as close to the construction as practical. The curtain shall remain in place and be maintained until the construction activity is completed and the disturbed area is stabilized 1.
2. The ends of the silt curtain shall be securely anchored and keyed into the shoreline to fully enclose the area where sediment may enter the water.
3. A 2-foot gap shall exist between the weighted lower end of the curtain and the bottom of the waterway or waterbody.
4. Bottom anchors shall be used to hold the silt curtain in the same position relative to the bottom the waterway or waterbody without interfering with the function of the curtain. Anchors shall either be driven into the bottom of the waterway or waterbody or be weighted and attached to the curtain floatation device via an anchor line. Manufacture's recommendations shall be followed for the number and spacing of anchors.
5. Danger buoys shall be used as directed by the Coast Guard or DNR permit when working in navigable waters.
B. Material:
1. Reusable components of the silt curtain system shall be clean and free of potential exotic species. Fabric cannot be reused.
2. The silt curtain shall be constructed from heavy woven filter fabric to allow water to pass through the barrier yet retain sediment. All fabric seams shall be heat sealed or sewn. Silt curtain fabric shall conform to the specifications in Table 1.
3. Flotation devices shall be flexible, buoyant units contained in an individual floatation sleeve or collar attached to the curtain. Use expanded polystyrene logs or equivalent having a 49 square inch minimum end area. Do not use polystyrene beads or chips. Buoyancy provided by the floatation device shall be sufficient to support the weight of the curtain and maintain a freeboard of at least 3 inches above the water surface level.
4. Top load lines shall consist of 5/16 inch steel cable.
5. Bottom load lines shall consist of a minimum ¼-inch steel chain incorporated into the bottom hem of the curtain. Larger chain sizes may be used where additional weight to serve as ballast to hold the curtain in a vertical position is required.
VI. Considerations
A. Sediment that has settled out by the silt curtain should only be removed as directed by the regulatory authority because re-suspension of sediment will likely occur during the removal process. Use of polymers may help prevent resuspension of sediment. See WDNR Technical Standard 1051 Sediment Control Water Application of Polymers for further guidance.
B. Silt curtains are meant to manage sediment in the waterbody. The best way to prevent sediment from entering the waterbody is through the implementation of effective upland erosion control, stopping sediment transport at its source.
VII. Plans and Specifications
Plans and specifications for installing a silt curtain shall be in keeping with this standard and shall describe the requirements for applying the practice to achieve its intended purpose:
A. Location of silt curtain.
B. Material specification conforming to standard.
C. All plans, standard detail drawings, or specifications shall include schedule for installation, inspection, and maintenance. The responsible party shall be identified.
VIII. Operation and Maintenance
A. Silt curtains shall be inspected daily and repaired if necessary.
B. Regardless of upland stabilization conditions silt curtains shall not be removed until the water behind the curtain has equal or greater clarity than the waterway or waterbody. Soil particles shall be allowed to settle for a minimum of 24 hours prior to removal of the curtain.
C. Care shall be taken when removing the silt curtain to minimize the release or re-suspension of accumulated sediment.
D. To prevent the spread of exotic species silt curtains shall not be reused on other sites. Buoys and chains can be reused but shall be either disinfected with vinegar or cleaned with hot water greater than 104 deg. F then allowed to completely dry for a minimum period of five days. If there are any questions about the occurrence of zebra mussels, Eurasian water-milfoil, or other aquatic invasive species in a waterbody that you are working in or intend to work in contact your local DNR staff.
IX. References
Virginia Erosion and Sediment Control Handbook, Third Edition, 1992
WisDOT Facilities Development Manual: Chapter
10, Section 10, Subject 43, Silt Screen
X. Definitions
Stabilized (V.A.1): Means that all land disturbing construction activities at the construction site have been completed, and that a uniform perennial vegetative cover has been established with a density of at least 70% of the cover for the unpaved areas and areas not covered by permanent structures, or that employ equivalent stabilization measures.
Stone Tracking Pad and Tire Washing
1057 (08/03)
Wisconsin Department of Natural Resources
Conservation Practice Standard
Note: Words in the standard that are shown in italics are described in IX. Definitions. The words are italicized the first time they are used.
I. Definition
A stabilized pad of stone aggregate or tire washing station located at any point where traffic will egress a construction site.
II. Purpose
The purpose of this standard is to reduce off-site sedimentation by eliminating the tracking of sediment from construction sites.
III. Conditions Where Practice Applies
Either a stone tracking pad or tire washing station shall be used at all points of construction egress. This standard applies where construction traffic is likely to transport sediment off site.
IV. Federal, State, and Local Laws
Users of this standard shall be aware of applicable federal, state, and local laws, rules, regulations, or permit requirements governing the use and placement of this practice. This standard does not contain the text of federal, state, or local laws.
V. Criteria
This section establishes the minimum standards for design, installation and performance requirements.
A. Tracking Pad:
1. The tracking pad shall be installed prior to any traffic leaving the site.
2. The aggregate for tracking pads shall be 3 to 6 inch clear or washed stone. All material to be retained on a 3-inch sieve.
3. The aggregate shall be placed in a layer at least 12 inches thick. On sites with a high water table, or where saturated conditions are expected during the life of the practice, stone tracking pads shall be underlain with a WisDOT Type R geotextile fabric to prevent migration of underlying soil into the stone.
4. The tracking pad shall be the full width of the egress point. The tracking pad shall be at a minimum 50 feet long.
5. Surface water must be prevented from passing through the tracking pad. Flows shall be diverted away from tracking pads or conveyed under and around them by using a variety of practices, such as culverts, water bars1, or other similar practices.
B. Tire washing: If conditions on the site are such that the sediment is not removed from vehicle tires by the tracking pad, then tires shall be washed utilizing pressurized water before entering a public road.
1. The washing station shall be located on-site in an area that is stabilized and drains into suitable sediment trapping or settling device.
2. The wash rack shall consist of a heavy grating over a lowered area. The rack shall be strong enough to support the vehicles that will cross it.
C. Rocks lodged between the tires of dual wheel vehicles shall be removed prior to leaving the construction site.
VI. Considerations
A. Vehicles traveling across the tracking pad should maintain a slow constant speed.
B. The best approach to preventing off-site tracking is to restrict vehicles to stabilized areas.
C. It is always preferable to prevent sediment from being deposited upon the road than cleaning the road later. Sediment on a road can create a safety hazard as well as a pollution problem.
D. Any sediment tracked onto a public or private road should be removed by street cleaning, not flushing, before the end of each working day.
VII. Plans and Specifications
A. Plans and specifications for installing tracking pads shall be in keeping with this standard and shall describe the requirements for applying the practice to achieve its intended purpose. The plans and specifications shall address the following:
1. Location of all points of egress with tracking pad locations shown
2. Material specifications conforming to standard
3. Schedule for installation and removal
4. Standard drawings and installation details
5. Stabilization after removal
B. All plans, standard detail drawings, or specifications shall include schedule for installation, inspection, and maintenance. The responsible party shall be identified.
VIII. Operation and Maintenance
A. Tracking pads and tire washing stations shall, at a minimum, be inspected weekly and within 24 hours after every precipitation event that produces 0.5 inches of rain or more during a 24-hour period.
B. The tracking pad performance shall be maintained by scraping or top-dressing with additional aggregate.
C. A minimum 12-inch thick pad shall be maintained.
IX. Definitions
