Soil erosion is defined as the wearing away of land by the action of wind, water, or gravity or a combination of wind, water, and gravity. The result of this wearing away of land is that soil particles are dislodged and put into motion. Soil particles that are in transport or have been transported to new locations and deposited are called sediment. The sedimentation of Michigan’s water resources can adversely affect plant, animal and aquatic life by altering the size or shape of streams, or covering the spawning habitat of aquatic species.
One way to combat sedimentation in Michigan’s water resources is to control the erosion of soil particles from construction sites. Construction projects often require the removal of layers of vegetative cover in order to complete the construction of subgrade structural components or other foundational aspects of a project, thus increasing the likelihood of erosion. With proper design considerations and planning, soil erosion can be minimized and sediment can be controlled so it does not leave the site.
Gratiot County SESC Program
The Gratiot County Permits Office accepts the responsibility for the effective control of soil erosion and sedimentation, through issuance of permits, field inspections, and compliance and enforcement within its jurisdiction pursuant to Part 91, Soil Erosion and Sedimentation Control, 1994 PA 451, as amended, the administrative rules and the Gratiot County Soil Erosion and Sedimentation Control Ordinance. This guidebook is designed to serve as a guidance document for Gratiot County Permits Office personnel who are involved in the review of permit applications, project documents, and the inspection of construction sites for soil erosion and sedimentation control measures. Section IV, Detail Drawings and Specifications, of the guidebook contains SESC measures to be incorporated into the design of construction projects.
Soil erosion and sedimentation control (SESC) will be a priority during and after all phases of construction. All SESC plans will be reviewed and approved by the Permits Office prior to issuance of a permit. In addition, a storm water permit or written waiver (if a storm water permit is not applicable) issued by the Gratiot County Drain Commissioner pursuant to the Gratiot County Administrative Guidelines for Storm Water management must be obtained prior to issuance of an SESC permit.
If the landowner and/or authorized agent designates another person as the “on-site authorized agent” to take responsibility for implementation of the permit requirements the designated “on-site authorized agent” shall jointly accept these responsibilities by signing an agreement with the landowner and provide a copy to the Permits Office for approval. Soil erosion and sedimentation control measures, including the approved construction contractor's implementation and sequencing plan, will be in place and functioning before the soil is disturbed or as specified in the construction schedule. All temporary control measures will remain in place and maintained until the impacted areas are permanently stabilized.
Individuals within the Permits Office who are responsible for projects required to comply with Part 91, are required to hold a valid SESC Certificate of Training from the Michigan Department of Environmental Quality (MDEQ) prior to appointment. This includes the County Building Official who is responsible for day to day operations and the SESC Field Inspector. The Deputy Permits Officer who provides clerical support and the SESC Clerk/Typist will be required to obtain a valid SESC Certificate of Training from the MDEQ within one year of appointment. Individuals working for consultants who provide design, review and inspection services will be required to hold a valid SESC Certificate of Training from the MDEQ.
Principles of SESC
The Permits Office recognizes seven basic principles of soil erosion and sedimentation control. These principles will be considered by the Permits Office during application and plan review, and inspection. The principles are:
- Design and construct terrain features such as slopes and drainage ways to minimize the erosion potential of the exposed site based on the soil type, time of year, proximity to waterways, duration of exposure, length and steepness of the slope, and the anticipated volume and intensity of runoff.
- Minimize the surface area of unstabilized soils left unprotected and vulnerable to runoff and wind at any one time.
- Minimize the amount of time that unstabilized soil areas are exposed to erosive forces.
- Protect and shield exposed soil areas with a cover of live vegetation, mulch, or other approved erosion resistant material during the temporary and permanent control periods of construction.
- Avoid concentrating runoff. When concentrated runoff cannot be avoided, runoff velocities shall be reduced to non-erosive velocities.
- Eroded sediments will be trapped on-site with temporary and permanent barriers, basins or other sediment retention devices while allowing for the controlled discharge of runoff waters at non-erosive velocities.
- Implement a continuous inspection and maintenance program.
The Permits Office shall review the SESC plans to assure they include at a minimum all information required in R323.1703 of Part 91 and the Gratiot County SESC Ordinance.
Contractors will be required to provide a separate line item cost estimates for:
- Construction sequencing
- Installation, maintenance and removal of temporary SESC control measures
- Installation and maintenance of permanent SESC control measures
The Permits Office is responsible for inspection during all phases of construction to ensure that SESC measures are installed in accordance with the SESC implementation plan, installed in a timely manner, maintained, and effectively controlling soil erosion and off-site sedimentation.
Based on-site conditions, the Permits Office SESC Field Inspector may approve "minor" adjustments to the overall SESC strategy such as relocating or adding silt fence, check dams, or modifying inlet protection controls. Any "major" deviations from the plan requirements, especially in areas with concentrated flows (except check dams), require the landowner or authorized agent to prepare and submit plans to the Permits Office for review and approval prior to implementation. Prior review and approval is not required if the changes are needed to mitigate the effects of a pending sediment release.
Gratiot County generally describes soil erosion project into three major program categories summarized as follows:
|Project Type||Frequency of Inspections|
|Major Project - A commercial project or large residential project with a plan that is generally complex in nature||1 to 2 times per month and after a significant rain event|
|Minor Project - A standard residential or other type of project with a plan that is relatively simple and routine in nature||1 to 2 times every other month and after a significant rain event|
|Ongoing Concerns - A project that is operating over a period of one year or more such as a sand or gravel mining operation or other similar types of projects||3 to 4 times per year and after a significant rain event|
The project descriptions and frequency of inspections are meant to serve as general guidelines only. Gratiot County recognizes each project has unique aspects and may require more or less inspections depending on the weather, nature and location of the project, compliance and enforcement issues, knowledge of the landowner, and other related issues. The standard operating procedure of the County is to take into account these and other factors when a project becomes active and an inspection schedule is established. Gratiot County reserves the right to change the inspection schedule of any project at any time.