All stockpiles shall be designed and constructed according to the following standards:
Existing stockpiles shall be incorporated or extended to the extent possible.
Water shall be drained away from the top of any stockpile in a manner which will not adversely affect the structural stability of the stockpile and will minimize erosion.
All runoff and drainage control measures shall be designed to withstand a 100-year frequency, 24-hour duration storm as developed using good hydraulic and hydrologic practices.
If runoff from stockpiles has caused or is likely to cause violations of water quality standards, the runoff shall be collected and held in a settling basin until it meets, or is treated to meet, effluent limitations.
Runoff or drainage controls shall be designed by a qualified person proficient in hydrologic analysis and water channel design.
When a water quality problem has occurred or is likely to result from leaching of stockpiled material, the commissioner shall require one or more of the following based on the type of material and the nature and location of the problem:
the design of a monitoring system and the monitoring of water quality;
the construction of an impermeable base pad to isolate the stockpile from the groundwater;
the construction of a permeable base pad containing soil material capable of absorbing and holding the toxic materials in the leachates;
the diversion of surface waters around and away from the stockpile;
covering of stockpiles to minimize the infiltration of precipitation;
the use of internal layers of soil or other material to hold the toxic materials in the leachate;
the use of material which controls pH of the leachate; and
the collection and treatment of leachate.
MS s 93.47
June 11, 2008
Official Publication of the State of Minnesota
Revisor of Statutes