MN Well Driller flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Minimum surface seal depth

A drilled well requires a continuous grout seal extending at least 20 feet below land surface, or deeper where unconsolidated material overlies bedrock, to prevent surface contamination from entering the annulus.

Annular grout volume formula

Volume equals 0.7854 times the difference between hole diameter squared and casing outside diameter squared, multiplied by sealed length, with a 10 to 15 percent excess added for washout and lost circulation.

Tremie grouting method

Grout is pumped from the bottom of the annulus upward through a pipe kept submerged in grout, which displaces water and prevents voids, bridging, and segregation that occur with free-fall placement.

Casing height above grade

Well casing must extend at least 12 inches above finished grade and at least 2 feet above the 100-year flood elevation where flooding is possible, with a watertight cap installed.

Neat cement grout mix

One 94-pound bag of Portland cement mixed with no more than 6 gallons of water; up to 5 percent bentonite by cement weight may be added to reduce shrinkage and settling.

Well development purpose

Development removes drilling fluid, fines, and sediment from the formation around the screen so the well yields clear water and reaches its intended specific capacity.

Filter pack sizing rule

Gravel pack is selected so the screen retains at least 90 percent of the pack, and the pack is sized to the formation's D50 grain size to prevent sand entry while maintaining flow.

Disinfection contact time

New or repaired wells are treated with a chlorine solution of at least 100 mg/L and left undisturbed for a minimum of 12 hours before pumping to waste and sampling.

Well abandonment sequence

Remove the pump, piping, and wiring; then remove or perforate the casing and fill the entire borehole with approved sealing material from bottom to land surface.

Approved abandonment sealants

Neat cement grout, sand-cement grout with no more than one part sand to one part cement, bentonite chips, and bentonite slurry are acceptable sealing materials for abandoned wells.

Bentonite chip placement

Chips are poured slowly by gravity through a tremie or hopper so they do not bridge in the borehole; the seal must reach land surface with no voids.

Flowing well abandonment

A flowing or artesian well must be sealed with grout placed to control the flow; simply capping the casing is not an acceptable abandonment method.

Grout curing before drilling

Placed grout must set at least 24 hours, and longer in cold weather or for large volumes, before drilling resumes or the well is developed, so the seal is not damaged.

Abandonment reporting deadline

The sealing method, materials, and depths must be reported to the Minnesota Department of Health within 30 days of completing the abandonment work.

Confining layer seal requirement

Where a confined aquifer is penetrated, the seal must extend through the confining layer so the well does not create a pathway between aquifers or to the surface.

Temporarily out-of-service well

A well not in use but intended for future service must keep intact casing and a watertight cap; it is not abandoned until permanently sealed and reported.

Sand-cement grout limit

Sand-cement grout used for sealing may contain no more than one part sand to one part cement by volume, which keeps the mix pumpable and strong enough to seal.

Minnesota well statute

Minnesota Statutes Chapter 103I is the well law that authorizes the Department of Health to regulate well construction, sealing, and water supply safety.

Minnesota well rules chapter

Minnesota Rules Chapter 4725 contains the technical requirements for wells and borings, including setbacks, construction standards, sealing, and reporting.

Well record filing deadline

The well contractor must submit the construction or sealing record to the Minnesota Department of Health within 30 days after the work is completed.

Licensing requirement

Well construction and sealing must be done by a licensed well contractor or by a person working under one; the contractor is responsible for compliance and reporting.

Owner-builder well exception

A person who owns and occupies the property may construct a domestic well only if a permit is obtained and all rule requirements are met; it is a narrow exception.

Septic setback distance

A well must be at least 50 feet from a septic tank and at least 50 feet from the soil treatment system, with larger setbacks for other contamination sources.

Property line setback

A well must be at least 20 feet from a property line unless the adjoining owner gives written consent, and it may not be placed in a floodway.

Local ordinance precedence

Local governments may adopt well ordinances stricter than the state rule, and the driller must comply with whichever requirement is more stringent.

Variance request procedure

A written variance must be requested from the Department of Health and approved before nonstandard construction begins; approval after the fact is not permitted.

Nitrate standard

The drinking water limit is 10 mg/L nitrate as nitrogen; above that level the owner must be warned not to give the water to infants under six months.

Coliform bacteria standard

Total coliform must be absent; a positive result requires resampling and, if confirmed, correction of the wellhead, casing, or seal before the water is used.

Sterile sample collection

Samples are collected in sterile containers from a purged tap or wellhead, with no chlorine residual present, because disinfectant can interfere with bacteriological results.

Arsenic maximum contaminant level

The arsenic standard is 10 micrograms per liter; arsenic occurs naturally in some Minnesota aquifers and requires testing and treatment when exceeded.

New well sampling requirement

A new well must be tested for coliform bacteria and nitrate after disinfection and before being placed in service, with results given to the owner.

Persistent bacteria response

If disinfection and retesting do not clear a bacteriological problem, the driller must inspect the casing, seal, and wellhead for defects and make repairs.