§ 15.55.060. General standards for domestic wells.

A.

Prohibited wells. Well pits are prohibited. The development services department may, at its discretion, allow an existing well pit to remain in use if it is shown the pit provides adequate protection against flooding.

B.

Well location and minimum setbacks. The location of a well shall be at a site readily accessible year round for testing, repair or maintenance purposes. The minimum separation requirements between wells and other specified facilities or areas shall be:

TABLE A-1

SEPARATION OF WELL FROM:	MINIMUM SEPARATION DISTANCE IN FEET
Private sewer line	25
Curtain drain	25
Petroleum Hydrocarbon storage tank	25
Sewer trunk line	75
Any other source of potential contamination	75
Holding tank	75
Septic absorption field	100
Sewer manhole or cleanout	100
Septic tank	100
Animal containment areas	50
Manure/animal excreta storage areas	100

 

C.

Well drilling. The commercial drilling of a well and subsequent rehabilitation or deepening operation shall be performed by a licensed well driller. Any drilling method used in the construction of a well shall meet the following requirements:

1.

The well driller shall notify the development services department of the proposed date of commencement of any drilling or rehabilitation or deepening or decommissioning operation prior to the start of operation.

2.

The ground surface surrounding the well for at least ten feet shall be sloped or contoured to allow surface water to drain away from the well.

3.

The well driller shall exercise reasonable care during excavation or drilling operation to prevent contamination to any aquifer.

4.

Organic drilling fluid may be used only if the fluid is approved for such use by the National Sanitation Foundation (NSF) or by an equivalent organization; these fluids are listed in NSF Standard 60 and NSF Standard 61 and in associated product listings described in these two standards.

5.

Water used in the drilling process shall be obtained from a source providing potable water.

6.

Water wells shall be drilled and cased with non-perforated pipe to a minimum depth of 40 feet, in unconsolidated materials and in bedrock. If bedrock is encountered at a depth greater than 20 feet and less than 40 feet, then the easing shall extend a minimum of 20 feet into the bedrock. Where it is necessary to case bedrock to meet these requirements, an oversized borehole shall be drilled from surface to the required depth into the bedrock. The resulting oversized borehole shall be grouted in accordance with section 15.55.060D.2.

7.

A well completed in unconsolidated formations shall be constructed so water only enters the well from a single water producing zone.

D.

Well casing. All casing shall be installed with NSF approved potable water materials in new or like new condition, free of pits or breaks. The following wall thickness shall be used, except all casing greater than the nominal size of six inches shall have a wall thickness of at least 0.250 inches:

TABLE A-2

NOMINAL SIZE (INSIDE DIAMETER) (INCHES)	OUTSIDE DIAMETER (INCHES)	WALL THICKNESS (INCHES)
4	4.50	0.237
5	5.50	0.244
5.5	6.00	0.245
6.125 (6 1/8 ")	6.625 (6 5/8 ")	0.250

 

1.

Joints. All casing joints shall be screw-coupled or welded and shall be water tight. If welded joints are used, the weld shall be at least as thick as the thickness of the well casing.

2.

Grouting. Grouting the outer annular space is necessary to prevent shallow non-potable water or surface waters from entering into a potable water aquifer. All wells shall be ground with bentonite slurry or granules as follows:

a.

From the pitless adapter level to at least ten feet below the pitless adapter or, from the surface to a minimum 20 feet below the surface;

b.

If bedrock is encountered as described in section 15.55.060C.6., the following grouting procedures shall be followed:

i.

The permanent well casing shall be grouted from the bottom of the borehole up using high solids bentonite slurry (minimum 20 percent solids content). The oversized bore shall be stabilized to eliminate caving and sloughing.

ii.

If the permanent casing is used as a tremie to place the grout by circulating from the up, a minimum one-inch annulus spacing from the bottom of the bore to surface shall be required.

iii.

If a temporary casing is used to stabilize the oversized bore, it shall be removed upon completion of grouting procedures.

3.

Pitless adapters. Pitless adapters shall be installed by a certified pump installer, a certified well driller or by an excavator under the supervision of a certified pump installer or well driller. The burial depth and type of pitless adapter installed shall be recorded on the pump installation log pursuant to section 15.55.060J. When installed, pitless adapters shall be one of the types approved by the development services department.

4.

Well casing stick up. All well casing shall extend a minimum of 18 inches above the finished grade, with the ground sloped to drain away from the casing.

5.

Well seal. The top of the casing shall be closed with a sanitary well seal of a type approved by the development services department.

6.

Drive shoe. When the casing is driven or otherwise forced into the well bore, the bottom of the casing shall be protected from damage by the use of a drive shoe or mechanical device.

7.

Perforating or slotting. Perforating or slotting of the casing utilized for the purpose of allowing water to enter the well from water producing zones encountered above the bottom of the casing shall not extend higher than 40 feet below the ground surface, unless it meets the requirements of section 15.55.060C.6.

E.

Well accessories. The commercial installation of well accessories shall be performed by a certified well driller or certified pump installer.

F.

Minimum water well production and testing. If the minimum sustained rate of production and recovery of a well is less than 150 gallons per day per bedroom, as determined by a well yield test and/or recovery test, water storage facilities shall be installed.

1.

Well yield testing. Upon completion of a well, a well yield test shall be performed by a certified well driller or pump installer or a certified civil engineer or a hydrogeologist. The well yield test shall be performed by bailing, air lifting or by pumping. The well yield test shall accurately determine the well's sustained productivity from test data including, but not limited to, static water level, pumping water level, drawdown rate, recovery rate or any other information useful in determining the sustained producing rate. If the well's initial sustained production rate is less than one gallon per minute, the development services department may require additional testing by alternative methods.

2.

Water quality testing. Drinking water from the well shall be properly sampled and analyzed by a certified laboratory for levels of total coliform bacteria, other bacteria, arsenic and nitrate. The results of this sampling shall be submitted to the development services department within 30 days of the completion of the well. The levels of total coliform and other bacteria shall conform to drinking water limits established in section 15.55.060K. For other contaminants, including arsenic and nitrate, the departments shall use the current USEPA public drinking water standards as a guideline to trigger actions deemed necessary to protect the public health. Such actions shall be taken in partnership by the Anchorage Health Department and the development services department and may include, but are not limited to, issuing a health advisory, discontinuation of the use of water from the well for drinking water, decommissioning of the well, or requiring water treatment. The above departments may require other contaminants to be analyzed if deemed necessary for the protection of public health.

G.

Well disinfection. Wells shall be disinfected as follows:

1.

New or deepened wells. Immediately after completion of drilling or deepening wells, the well shall be disinfected. After the well is flushed of drill cuttings, apply a chlorine compound proportioned to provide a concentration of at least 50 ppm as free chlorine to the entire volume of water in the well bore. The chlorine shall be introduced into the well in a manner which shall distribute it throughout the entire water depth. Allow the chlorinated water to remain in the well undisturbed for at least 24 hours.

2.

Hydrofractured or redeveloped wells. While redeveloping or hydrofracturing wells and when possible, a free chlorine residual in the well of at least five ppm shall be maintained.

3.

Pump work. On completion of pump installation work, a chlorine compound proportioned to provide a concentration of at least 50 ppm as free chlorine to the entire volume of water in the well bore shall be applied. After chlorine is introduced, water shall be circulated in the well so it reaches all parts of the pumping equipment, inside and out. The chlorinated water shall remain in the well for at least one hour.

4.

Flushing. After the required disinfection time has expired, the well shall be flushed of all chlorinated water before being placed in service.

H.

Well identification. All wells shall be labeled with a durable form of construction information upon completion. The construction information source shall be secured to the well casing and contain the following information:

1.

The name of the drilling contractor;

2.

The date the well was completed;

3.

The total depth;

4.

The total depth of casing;

5.

The location and type of well completion;

6.

Static water level below the top of the casing;

7.

Yield; and

8.

Height of casing above finished grade.

I.

Well logs and as-built. The certified well driller shall provide a well log to the development services department within 30 days of completion of the well. The well log shall include at least the following pertinent information:

1.

The property owner's name;

2.

The legal description and street address;

3.

The method of drilling (rotary, cable tool, etc.);

4.

A description, relative depth, and thickness of each soil stratum penetrated from the ground surface to the total depth;

5.

The relative depth and thickness of each water bearing stratum (aquifer) penetrated;

6.

The total depth drilled;

7.

The length, diameter, wall thickness and type of casing used;

8.

A description of the liner (if used) and the length and setting depth;

9.

The depth and number of perforations, (if any) in the easing and/or liner;

10.

The type and location of any screens used;

11.

The static water level and drawdown level;

12.

The well production test results including the method of testing;

13.

The dates of commencement and completion of drilling operations;

14.

The number and date of the well drilling permit issued by the development services department;

15.

The name and address of the certified well driller; and

16.

A description of the method of disinfection process used upon completion of the well.

J.

Pump installation log. The certified pump installer or well driller shall provide a pump installation log to the development services department within 30 days of completion of the installation of a pump into a water well.

1.

The pump installation log shall include at least the following pertinent information:

a.

The property owner's name;

b.

The legal description and street address of the property;

c.

The date of the pump installation;

d.

The manufacturer's name, model and size of the pump installed;

e.

The depth from top of casing that the pump is installed;

f.

The number and date of the well drilling permit issued by the development services department;

g.

The name and address of the certified pump installer, or certified well driller or excavator; and

h.

A description of the method of disinfection used.

K.

Water quality standards. Water used for domestic purposes shall not contain concentrations exceeding the following ratios:

1.

Total coliform bacteria—0 colonies per 100 ml.

2.

Other bacteria—10 colonies per 100 ml.

L.

Well decommissioning. Wells shall be decommissioned by a certified well driller or a certified pump installer in accordance with this subsection:

1.

Permanent decommissioning. A well may be permanently decommissioned by one of the following methods:

a.

Perforate the casing from the bottom to within five feet of the land surface, remove the top five feet, then pressure grout the entire length.

b.

Withdraw the casing and fill the borehole with grout, or bentonite as the casing is being withdrawn.

c.

Cut off the casing at a point two feet below ground level and fill the casing with a bentonite slurry pumped from the bottom up or with bentonite chips poured in a bridge free manner. The top of the cut off casing shall then be sealed with a 0.25 inch thick (or thicker) plate firmly welded to the top of the casing.

(AO No. 96-98(S), § 6, 8-13-96; AO No. 2005-130, § 1, 1-1-06; AO No. 2018-118 , § 2, 1-1-19)