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The final step when all contributing drainage areas have been stabilized

Constructing infiltration systems.
Link to this table

Noncompliant construction Compliant construction
In these pictures, inlets to the infiltration basin were not protected, and sediment enters the basin from exposed soils on the still active construction site. The basin was not protected from sedimentation, and sediment runs off the side slopes and is deposited in the basin.
Inlets to the infiltration basin were not protected.PNG
Heavy equipment should work from outside of the infiltration basin so soils are not compacted. In this photo, the basin has been over-excavated as designed. The excavator sits outside the basin and uses a frost ripper to loosen the soils. The same process is used to incorporate a sand/compost mix into the basin.
Heavy equipment work from outside infiltration basin so soils not compacted.PNG
Sediment entering the basin from exposed soils on the construction site and from the side slopes clogs the system.
Sediment entering the basin clogs the system.PNG
Identifying infiltration areas with signs notifies staff, subcontractors and others to keep heavy machinery out, ensuring that soils are not compacted.
Identifying infiltration areas with signs.PNG
Months later, the construction project is complete. The basin captures rainfall from a small rain event but it doesn’t infiltrate. Costly repairs are required in order for it to function properly.
Basin captures rainfall from a small rain event but it doesn’t infiltrate.PNG
This photo shows a system that has been properly protected after construction. Contributing drainage areas have been stabilized and the basin has been protected with the orange silt fence from both sedimentation and compaction from vehicle traffic.
System that has been properly protected after construction.PNG
Avoid using heavy equipment to construct infiltration systems. Heavy equipment will compact soils in the system and infiltration rates will decrease or stop altogether. Once at final grade, the infiltration system should be staked off and marked so that heavy vehicles or equipment do not compact the soils.
Heavy equipment will compact soils and infiltration rates will decrease or stop.PNG
Infiltration is prohibited in certain areas – check the permit!
  • Areas that receive discharges from vehicle fueling and maintenance
  • Areas with less than 3 feet of separation from the bottom of the system and seasonally saturated soils, wetlands, and bedrock
  • Areas that receive discharges from industrial facilities not authorized to infiltrate under an Industrial Stormwater Permit
  • Areas where high levels of contaminants in soil or groundwater will be mobilized by infiltration
  • Areas with clay soils
  • Karst areas
  • Areas where infiltration rates are more than 8.3 inches/hour
  • Aareas within a Drinking Water Supply Management Area (DWSMA) as defined in Minn. R. 4720.5100, subp. 13., if the system will be located:
    • in an Emergency Response Area (ERA) within a DWSMA classified as having high or very high vulnerability as defined by the Minnesota Department of Health; or
    • in an ERA within a DWSMA classified as moderate vulnerability unless a regulated MS4 Permittee performed or approved a higher level of engineering review sufficient to provide a functioning treatment system and to prevent adverse impacts to groundwater; or
    • outside of an ERA within a DWSMA classified as having high or very high vulnerability, unless a regulated MS4 Permittee performed or approved a higher level of engineering review sufficient to provide a functioning treatment system and to prevent adverse impacts to groundwater


This page was last edited on 21 March 2019, at 14:49.

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