ISOLATION DISTANCES FROM A WATER-SUPPLY WELL – Distances must be measured horizontally from the water-supply well. The minimum isolation distance must be maintained between a new well and a contamination source, even if the contamination source is no longer in use. An isolation distance is not required if the contamination source and any related contaminated soil have been removed. A sensitive water-supply well must be located at least twice the indicated distance. A sensitive water-supply well is a well with less than 50 feet of watertight casing, and which is not cased below a confining layer or confining materials of at least 10 feet in thickness. A community public water-supply well must be a minimum of 50 feet from this contamination source. A well or boring may not be constructed inside a building. A well or boring may be located between 5 and 10 feet of an electric transmission line, gas pipe or LP tank if the well or boring is placarded, and work is not performed on the well or boring unless the electric line is deenergized and grounded or shielded, and the LP tank does not contain flammable gas. The 20-foot distance applies only to an irrigation well and a fertilizer chemigation supply tank. A community public water-supply well must be a minimum of 50 feet from a petroleum tank or container with a capacity between 56 and 1,100 gallons, unless the tank or container is used to fuel emergency pumping equipment and is located in a room or building separate from the community well.

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Isolation Distances From a Water-Supply Well

Well Management Program

Minnesota Department of Health

Minnesota Rules, Chapter 4725
Rules Relating to Wells and Borings
Effective date: August 4, 2008

 

The isolation distances below are from Minnesota Rules, chapter 4725.

Distances must be measured horizontally from the water-supply well. 

Minnesota Statutes, section 103I.205, subdivision 6, prohibits constructing, placing, or installing an actual or potential contaminant source from a well that is less than the minimum distance prescribed by rule.

The minimum isolation distance must be maintained between a new well and a contamination source, even if the contamination source is no longer in use.

An isolation distance is not required if the contamination source and any related contaminated soil have been removed.

Additional information and explanations can be found in the Rules Handbook, A Guide to the Rules Relating to Wells and Borings, or by contacting the Well Management Section.

If you have questions about isolation distances not listed here, please contact the Minnesota Department of Health Well Management Section.

Absorption area of a soil dispersal system
	average flow greater than 10,000 gallons/day		300		feet1
	serving a facility handling infectious or pathological wastes		150		feet1
	average flow 10,000 gallons/day or less		50		feet1
Agricultural chemical
	tank or container with 25 gallons or more or 100 pounds or more dry weight, or equipment filling or cleaning area without safeguards		150		feet
	storage or equipment filling or cleaning area with safeguards		100		feet
	storage or equipment filling or cleaning area with safeguards and roofed		50		feet
	buried piping		50		feet
	multiple tanks or containers for residential retail sale or use, no single tank or container exceeding, but aggregate volume exceeding 56 gallons or 100 pounds dry weight		50		feet
Anhydrous ammonia tank			50		feet
Animal
	feedlot, unroofed, 300 or more animal units		100		feet1
	feedlot, more than 1.0, but less than 300 animal units		50		feet1
	building or poultry building, including a horse riding area, more than 1.0 animal unit		50		feet1
	rendering plant		50		feet
	feeding or watering area within a pasture, more than 1.0 animal unit		50		feet1
	area to bury more than one animal unit		50		feet
	building, feedlot, confinement area, or kennel, 0.1 to 1.0 animal unit		20		feet1,2
Building, building projection, deck, overhang, permanent structure			3		feet3
Cesspool			75		feet1
Cistern or reservoir, buried, nonpressurized water supply			20		feet
Commercial compost site			50		feet
Construction or demolition debris disposal area			50		feet1
Cooling water pond, industrial			50		feet1
Deicing chemicals, bulk road			50		feet1
Drainfield (see Absorption area)
Dry well (sewage)			75		feet1
Electric transmission line			10		feet4
Electrical transformer storage area, oil-filled			50		feet
Elevator boring, not conforming to rule			50		feet
	conforming to rule		20		feet
Fertilizer chemigation tank, safeguarded, from irrigation well only			20		feet5
Floor drain, grate, or trough
	connected to a buried sewer		50		feet
	if buried sewer is air-tested, approved materials, serving one building, or two or less single-family residences		20		feet2
Frost-proof yard hydrant or discharge of a frost-proof hydrant draining into the soil,
	fire hydrant or flushing hydrant		10		feet
Gas (flammable or volatile) pipe			10		feet4
Grave or mausoleum			50		feet
Gravel pocket or French drain for clear water drainage			20		feet
Gray-water dispersal area			50		feet1
Hazardous substance
	tank or container, above ground or underground, 56 gallons or more, or 100 pounds or more dry weight, without safeguards		150		feet
	tank or container, above ground or underground, 56 gallons or more, or 100 pounds or more dry weight with safeguards		100		feet
	buried piping		50		feet
	multiple storage tanks or containers for residential retail sale or use, no single tank or container exceeding 56 gallons or 100 pounds, but aggregate volume exceeding		50		feet
Horizontal ground source closed loop heat exchanger buried piping			50		feet
Horizontal ground source closed loop heat exchanger buried piping and horizontal piping, approved materials and heat transfer fluid			10		feet2
Household solid waste disposal area, single residence			50		feet1
Interceptor, including a flammable waste or sediment			50		feet
Land spreading area for sewage, septage, or sludge			50		feet1
Landfill or dump, mixed municipal solid waste from multiple persons			300		feet1
Landfill, permitted demolition debris			300		feet1
Leaching pit			75		feet1
Liquid propane (LP) tank			10		feet4
Manure (liquid) storage basin or lagoon
	unpermitted or noncertified		300		feet1
	approved earthen liner		150		feet1
	approved concrete or composite liner		100		feet1
Manure (solid) storage area, not covered with a roof			100		feet1
Ordinary high water level of a stream, river, pond, storm water retention pond, lake, or reservoir			35		feet2
Petroleum
	tank or container, 1,100 gallons or more, without safeguards		150		feet
	tank or container, 1,100 gallons or more, with safeguards		100		feet
	tank or container, buried, between 56 and 1,100 gallons		50		feet
	tank or container, not buried, between 56 and 1,100 gallons		20		feet6
	buried piping		50		feet
Petroleum or crude oil pipeline to a refinery or distribution center			100		feet
Pit or unfilled space more than four feet in depth			20		feet
Pollutant or contaminant that may drain into the soil			50		feet1
Privy, nonportable			50		feet1
	portable (privy) or toilet		20		feet2
Sand filter, watertight; peat filter; or constructed wetland			50		feet
Scrap yard			50		feet
Seepage pit			75		feet1
Septic tank			50		feet
Sewage holding tank, watertight			50		feet
Sewage sump
	capacity 100 gallons or more		50		feet
	capacity less than 100 gallons, tested, conforming to rule		20		feet2
Sewage treatment device, watertight			50		feet
Sewer, buried
	collector, municipal, serving a facility handling infectious or pathological wastes, open-jointed or unapproved materials		50		feet
	approved materials, tested, serving one building, or two or less single-family residences		20		feet2
Solid waste transfer station			50		feet
Storm water drain pipe, 8 inches or greater in diameter			20		feet2
Swimming pool, in-ground			20		feet
Unused, unsealed well or boring			50		feet
Vertical heat exchanger (vertical) piping, conforming to rule			35		feet2
	horizontal piping conforming to rule		10		feet2
Wastewater rapid infiltration basin, municipal or industrial			300		feet1
Wastewater spray irrigation area, municipal or industrial			150		feet1
Wastewater stabilization pond
	municipal, 500 or more gallons/acre/day of leakage		300		feet1
	municipal, less than 500 gallons/acre/day of leakage		150		feet1
	industrial		150		feet1
Wastewater treatment unit tanks, vessels and components (Package plant)			100		feet
Water treatment backwash disposal area			50		feet1
Water treatment backwash holding basin, reclaim basin, or surge tank
	with a direct sewer connection		50		feet
	with a backflow protected sewer connection		20		feet
	Additional Isolation Distances For
	Community Public Water-Supply Wells
Highest water or flood level			50		feet
Property line, unless legally controlled through an easement			50		feet
1		A sensitive water-supply well must be located at least twice the indicated distance. A sensitive water-supply well is a well with less than 50 feet of watertight casing, and which is not cased below a confining layer or confining materials of at least 10 feet in thickness.
2		A community public water-supply well must be a minimum of 50 feet from this contamination source.
3		A well or boring may not be constructed inside a building except as provided for by Minnesota Rules, part 4725.2175.
4		A well or boring may be located between 5 and 10 feet of an electric transmission line, gas pipe or LP tank if the well or boring is placarded, and work is not performed on the well or boring unless the electric line is deenergized and grounded or shielded, and the LP tank does not contain flammable gas.
5		The 20-foot distance applies only to an irrigation well and a fertilizer chemigation supply tank meeting the requirements of Minnesota Rules, chapter 1505.
6		A community public water-supply well must be a minimum of 50 feet from a petroleum tank or container with a capacity between 56 and 1,100 gallons, unless the tank or container is used to fuel emergency pumping equipment and is located in a room or building separate from the community well; and is of double-wall construction with leak detection between walls; or is protected with secondary containment.

https://www.health.state.mn.us/communities/environment/water/wells/construction/isolate.html