Minnesota Stormwater Manual test page 5

Warning: This page is an edit and testing page use by the wiki authors. It is not a content page for the Manual. Information on this page may not be accurate and should not be used as guidance in managing stormwater.

Recommendations for snow storage

This section provides guidance and recommendations for identifying appropriate snow storage areas, storing snow in those areas, and operations and maintenance of snow storage areas.

Siting recommendations

Methods for identifying baseflow contribution

Consult local groundwater maps and/or reports if they are available. Examples includes a County geologic atlas. This method is easy to use and reasonably accurate in most cases. Compare water table (groundwater) elevations to surface water elevations. This method is relatively easy to use if groundwater elevation data exists, but it is subject to inaccuracies as water levels fluctuate. Utilize existing reports from local studies. Examples include using information from remediation studies. These reports are reasonably accurate if the study was conducted near the receiving water. Baseflow separation methods are accurate but data intensive unless monitoring data exist for the receiving water. Link here for a video on computing baseflow using baseflow separation.

• Identify receiving waters and assess the risk to them. Although identifying the contribution of baseflow to receiving waters can be challenging, it is important if meltwater will infiltrate and recharge groundwater. Potential receiving waters include the following.
  • Streams and rivers with a significant baseflow component
  • Streams and rivers with low baseflow component
  • Lakes and wetlands with a baseflow component
  • Lakes and wetlands with limited baseflow
  • Groundwater
• Consult with your local community or municipality for technical guidelines on snow site management and operations.
• Estimate how much snow disposal capacity is needed for the season so that an adequate number of disposal sites can be selected and prepared. Plan on snow storage capacity equal to 20-30 percent of the snow volume from the source area.
• Determine potential pollutants of concern from the snow source areas
• Considering potential pollutants of concern, when practicable, designate snow storage areas in locations that enable runoff to be directed to stormwater BMPs for treatment prior to discharge to a receiving water, including groundwater.
• Snow storage should be avoided in the following situations.
  • Within a floodplain
  • Within 100 feet of active karst or areas where fractured bedrock is within 50 feet of the land surface
  • Within setback distances from receiving waters
  • On permeable soils (Hydrologic Soil Group A) where infiltration is not recommended or is prohibited under the Minnesota Construction Stormwater General Permit
  • In sanitary landfills, quarries, and gravel pits
  • In sections of parks or playgrounds that will be used for direct contact recreation after the snow season
  • In a receiving water (e.g. lake, river, wetland)
• Prioritize potential sites based on the following selection criteria.
  • Upland sites are preferred
  • Slopes should be less than 6 percent, with slopes less than 2 percent preferred
  • Site that can be used indefinitely are preferred, particularly if the site can be engineered to minimize environmental impacts
  • Preference is for storage on permeable material that meets typical stormwater design standards found in the Minnesota Stormwater Manual (e.g. 3 feet separation to seasonal high water table)

Site recommendations

• Storage
  • Snow should not be stored in stormwater treatment BMPs.
  • Snow may be stored above a vegetated filter strip
  • Do not locate snow storage areas on top of drain inlets.
  • Where applicable, locate storage areas outside of jurisdictional snow storage ROWs (usually 15-20 feet off of roadway).
  • Avoid siting snow storage on compacted or poorly draining soils (D soils), unless the meltwater is diverted to a treatment BMP that can treat the water quality volume.
  • For snow that may contain elevated levels of pollutants (e.g., commercial parking lots or roads), site snow storage on an impervious surface that drains to a stormwater treatment BMP.
  • Employ concave landscaped areas rather than mounded landscapes for snow storage.
  • Locate snow storage areas to maximize solar exposure and away from primary roadways to the greatest extent feasible
• Site
  • Clearly identify the boundaries of the snow storage area to be visible under winter conditions.
  • When storing snow in close proximity to sensitive receiving waters, construct a berm around the perimeter of the snow storage area to contain the snowmelt or construct a vegetated filter strip between the receiving water and the snow storage area.
  • When storing snow in landscaped areas, plant with native and adapted species tolerant of snow storage (perennials that die back annually and shrubs/trees that can bend with weight, but not break).
  • For unpaved snow storage areas where snowplowing equipment will operate, the snow storage area should be covered with gravel or plowed to maintain 12 inches of packed snow to reduce soil disturbance and soil compaction.
  • Snow storage areas should be maintained to reduce erosion and to ensure easy removal of accumulated pollutants or sediments such as sand, road dirt, trash and salts.
  • A silt fence, earthen berm or equivalent barrier should be placed securely on the downgradient side of the snow disposal site. These types of structures can be used to direct meltwater and surface runoff to settling ponds or detention basins and to minimize the possible seepage of contaminants into groundwater. If earthen berms or channels are used to contain or direct the flow of melt water they should be stabilized to prevent soil erosion during high flows.
  • Plant stockpile areas with salt-tolerant ground cover species
• Meltwater
  • When feasible, route meltwater to an appropriate stormwater treatment BMP. This is highly recommended if downstream receiving waters are sensitive to or impaired for pollutants of concern in the stored snow.
  • Provide appropriate pretreatment when routing meltwater to a downstream BMP. This may be achieved within the storage area if the storage area provides adequate storage volume to trap sediment left behind by melting snow
  • Meltwater should cross a gravel or erosion resistant buffer zone between the filter berm and surface water.
  • Sites which do not drain to treatment BMP should be contained by a snow fence, filter berm, small detention basin and buffer zone ( between the filter berm and storm sewer). An example of such a site might be a gravel parking lot which has sewer drainage.

Inspection and maintenance

• Before and after winter, clean the designated snow storage area of accumulated sand, trash, and debris, and inspect any associated drainage outlets or conveyance facilities for damage or erosion.
• Before and after winter, repair any damage or erosion that may have occurred to the snow storage area from snow removal equipment or other snow storage activities.
• Restore the soil if needed. Regrade if channelization from snowmelt or flowing water has occurred. Reseed with appropriate vegetation.
• Assess and if necessary, rehabilitate the infiltration capacity of the storage area and confirm conveyance facilities are functional.
• Monitor the quality of snowmelt