Required and recommended minimum vertical and horizontal separation distances. This represents the minimum distance from the infiltration practice to the structure of concern. If the structure is above-ground, the distance is measured from the edge of the BMP to the structure. If the structure is underground, the vertical separation distance represents the distance from the point of infiltration through the bottom of the system to the structure, while the horizontal separation (often called setback) distance is the shortest distance from the edge of the system to the structure.
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Structure Distance (feet) Requirement or recommendation Note(s)
Vertical Saturated soil 3 Requirement1
Bedrock 3 Requirement1
Horizontal Public supply well 100 for sensitive wells; 50 for others3 Requirement
Building/structure/property line2 10 Recommended
Surface water none unless local requirements exist If nearby stream is impaired for chloride, see [1]
Septic system 35 Recommended
Contaminated soil/groundwater No specific distance. Infiltration must not mobilize contaminants.
Slope 200 Recommended from toe of slope >= 20%
Karst 1000 up-gradient 100 down-gradient Requirement1 Active karst

1 Required under the Construction Stormwater General Permit
2 Minimum with slopes directed away from the building
3If treating an average of 10,000 gallons per day; otherwise separation distance is 300 feet

This page was last edited on 7 July 2021, at 20:25.


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