m |
|||
Line 4: | Line 4: | ||
Projects that will either extend more than one season or will still be active during the winter months need to take special considerations when planning for winter shutdown or an active winter construction season. A winter construction plan should be developed to specifically address shutdown procedures or active construction plans. Projects that plan to continue construction during the winter seasons should sequence construction events such that areas having high potential for erosion and sedimentation be fully constructed and stabilized prior to the presence of frozen conditions whenever possible. | Projects that will either extend more than one season or will still be active during the winter months need to take special considerations when planning for winter shutdown or an active winter construction season. A winter construction plan should be developed to specifically address shutdown procedures or active construction plans. Projects that plan to continue construction during the winter seasons should sequence construction events such that areas having high potential for erosion and sedimentation be fully constructed and stabilized prior to the presence of frozen conditions whenever possible. | ||
− | === | + | ===Shutting down construction sites for winter=== |
All winter shutdown activities should be performed before frozen conditions are present and must be completed within 14 days following the end of construction for the season. BMPs should not be installed on top of snow when used as part of winter shutdown. | All winter shutdown activities should be performed before frozen conditions are present and must be completed within 14 days following the end of construction for the season. BMPs should not be installed on top of snow when used as part of winter shutdown. | ||
− | *Seed all proposed vegetated areas | + | *Seed all proposed vegetated areas to ensure germination. |
− | *Stabilize all slopes no later than October 15th with either rock, permanent or temporary vegetation, straw mulch secured with netting (slopes less than 15%), erosion control blanket (slopes 15% or greater). Vegetated slopes that have not germinated with at least 70% cover | + | *Stabilize all slopes no later than October 15th with either rock, permanent or temporary vegetation, straw mulch secured with netting (slopes less than 15%), erosion control blanket (slopes 15% or greater). Vegetated slopes that have not germinated with at least 70% cover should be augmented with another method in these areas. |
*Stabilize all areas of bare soil (not including road, parking and staging areas) with a temporary seed mix or straw mulch crimped into the soil. | *Stabilize all areas of bare soil (not including road, parking and staging areas) with a temporary seed mix or straw mulch crimped into the soil. | ||
*Apply temporary seed or mulch stockpiles of soil materials with hay or straw at twice the normally recommended rate, with a minimum thickness of 3 inches having 80% to 90% cover. A 4-inch layer of erosion control mix may also be used. | *Apply temporary seed or mulch stockpiles of soil materials with hay or straw at twice the normally recommended rate, with a minimum thickness of 3 inches having 80% to 90% cover. A 4-inch layer of erosion control mix may also be used. | ||
− | *Install all sediment barriers with adequate area to allow access for inspection and maintenance. Install vertical markers every 100 feet to identify their locations during melt conditions | + | *Install all sediment barriers with adequate area to allow access for inspection and maintenance. Install vertical markers every 100 feet to identify their locations during melt conditions. |
*All road, parking and staging areas that have not been fully constructed prior to winter shutdown should be stabilized with a minimum of 3 inches of a sand and gravel mix with a gradation such that less than 12% of the sand passes the number 200 sieve. | *All road, parking and staging areas that have not been fully constructed prior to winter shutdown should be stabilized with a minimum of 3 inches of a sand and gravel mix with a gradation such that less than 12% of the sand passes the number 200 sieve. | ||
Projects that will either extend more than one season or will still be active during the winter months need to take special considerations when planning for winter shutdown or an active winter construction season. A winter construction plan should be developed to specifically address shutdown procedures or active construction plans. Projects that plan to continue construction during the winter seasons should sequence construction events such that areas having high potential for erosion and sedimentation be fully constructed and stabilized prior to the presence of frozen conditions whenever possible.
All winter shutdown activities should be performed before frozen conditions are present and must be completed within 14 days following the end of construction for the season. BMPs should not be installed on top of snow when used as part of winter shutdown.
Construction during the winter months presents many additional challenges that require modifications to traditional construction practices in order to continue with work. Typically, a winter construction plan should be followed once the ground begins to freeze. Frozen ground can cause equipment slippage during operation, make excavations difficult or impossible with the available equipment, and material stockpiles can freeze, which hinders the ability to achieve adequate compaction or uniformly distribute materials. In addition to the information provided below, MnDOT also includes additional resources.
Winter construction plans typically include the following provisions:
As winter construction progresses, there will be additional needs for stabilization, which cannot be addressed with traditional methods.
Typical temporary winter BMPs
Link to this table
Sediment barriers | Erosion control (not to be installed on more than 1" of snow) |
---|---|
Erosion control mix berms | Straw mulch (blankets, disc or crimp into soil or snow) |
Continuous contained berms | Erosion control blankets |
Sand bag berms | Sand or stone on areas to be paved |
Prepare a snow management plan for the site to account for adequate storage of cleared snow through the winter and control of meltwater. Snow storage locations should be placed down slope of all disturbed areas, but not located within stormwater treatment BMPs. Snow mixed with significant amounts of soil should be stored in separate locations that are designed to handle larger volumes of sediment. See the management approaches section under [cold climate impact on runoff management] for additional recommendations.
Many earthwork operations can continue through the winter months on frozen soils with specific modifications.
Occasionally, it may be necessary to relocate frozen or saturated soils to continue with construction. Separate storage locations should be identified for storage of frozen soils and snow mixed with soil. During construction, if mid-winter melts occur over frozen soil, the saturated soil may be removed on access drives and stored in these locations. Additionally, during trenching and excavation operations, frozen soil may be removed and stored here as well to access the unfrozen subgrade. Do not fill excavations with frozen or saturated soils.
Shallow drainage paths with a minimum width of 2 feet should be placed within the soil stockpile areas to direct runoff to treatment BMPs for sediment control and prevent mixing with surrounding spring runoff.
Regardless of whether or not a construction site has been shut down for the winter, all installed BMPs must be monitored and corrective actions taken as necessary. Gravel, sandbags, erosion blankets, and mulch should be kept on site to address any immediate repair needs. Repairs to BMPs should be made immediately and any accumulated sediment should be remove upon each inspection.
Inactive construction sites:
Active construction sites:
During spring thaw, it may be necessary to suspend construction activities until soils are no longer saturated. Keeping vehicle travel areas free of snow at night and covered with snow during the day can help to maintain frost penetration in the ground. It is extremely important that all BMPs are being actively monitored and promptly maintained during the spring thaw period.
See cold climate impact on runoff management for recommendations for controlling snowmelt runoff.