The objective of is to provide temporary or permanent cover to disturbed or erodible surfaces, both during and upon completion of a development project. When implemented in conjunction with appropriate site water management, erosion control measures are extremely effective at limiting erosion potential and concomitant water quality concerns.
Temporary Stockpile Protection
As a preventative measure, all temporary stockpiled materials (PDF) should be covered with 6 mil polyethylene tarps in advance of any forecasted significant rainfall events or if they will remain in place for a period greater than or equal to 2 weeks. Polyethylene tarps must have overlapping margins that are folded and secured to prevent disturbance by wind and must extend a minimum of 0.5 metres beyond the toe of the stockpile to mitigate scour. Due to the potentially significant runoff generated from large polyethylene covered stockpiles, it is strongly recommended that silt fence is installed 1 metre off set from the toe of stockpile.
Temporary Slope Protection
Temporary cut slopes (PDF) greater than 2 to 1 (horizontally and vertically) should be treated with either 6 mil polyethylene tarps or rolled erosion control products rolled erosion control products (RECPs). Typically, polyethylene will be employed for temporary slope protection while RECPs would be applied to the finished grade of a cut-slope.
Lower gradient disturbed surfaces should be stabilized via the application of hand spread or mechanically blown straw mulch, applied at a minimum rate of 3.36 tonnes per hectare. It is recommended that any exposed surfaces which will remain inactive for a period of 2 months or greater receive seeding during the growing season to further mitigate the risk of erosion.
Rolled Erosion Control Products (RECPs)
Rolled Erosion Control Products (PDF) are considered temporary surface protection and are intended for application to surfaces to mitigate raindrop and rill-erosion. RECPs typically consist of biodegradable straw or coir materials, and are intended for use in conjunction with ground cover seeding to establish vegetative cover. RECPs may be utilized as temporary slope protection without seeding in some instances; however, this approach is usually not economical. RECPs must be installed per manufacturer’s specifications.
Hydraulically applied mulch products are applied as a pumped and aerated slurry and typically consist of small pieces of cellulose fiber applied to stabilize soil from wind and water erosion, and provide temporary protection for seeds to promote germination. Hydraulic mulches are typically applied in conjunction with seeding and include the use of a tackifier to stabilize the mulch application. Track walking with heavy machinery to provide surface depressions perpendicular to the flow paths may be employed to prepare surfaces prior to hydraulic mulching. Hydraulic mulches should be applied under optimal site conditions, and should be applied at least 24 hours prior to forecast rain events.
Application prior to forecast rain events allow the mulches and tackifiers to “set up” on slopes. Application rates of all hydraulic mulches require consideration of slope gradients, slope lengths, and adherence to manufacturer’s specifications.
Permanent Slope Protection
Upon completion of slope grading, the establishment of vegetative cover is critical in mitigating long-term erosion potential. Vegetation establishment may be achieved via seeding. Upon completion of final slope treatment, seeding combined with RECPs or hydraulically applied mulches should be applied at the earliest opportunity. Application of seed outside the growing season may require re-seeding in the following year to address seed losses due to frost impacts.
Mechanical or manual application of seed directly onto prepared surfaces. Seed applications should be applied at the rate specified by the seed supplier and include fertilizer amendments per manufacturer’s recommendations or results of soil fertility testing.
Hydraulic seeding is completed in conjunction with the application of a hydraulically applied mulch.