Idaho Admin. Code r. 58.01.08.510

Current through September 2, 2024

Section 58.01.08.510 - SITING AND CONSTRUCTION OF WELLS

Written approval by the Department is required before water from any new or reconstructed well may be served to the public. Any supplier of water for a PWS served by one (1) or more wells must ensure that the following requirements are met:

01.Site Approval. Prior to drilling, the site of a PWS well must be approved in writing by the Department. A well site evaluation report must be submitted prior to or concurrent with the PER for the well. The well site evaluation must take into account the proposed size, depth, and location of the well. The evaluation may include, but is not limited to the following types of information:

a. An evaluation of the quality of anticipated groundwater.

b. Identification of the known aquifers and the extent of each aquifer, based on the stratigraphy, sedimentation, and geologic structure beneath the proposed well site.

c. An estimate of hydrologic and geologic properties of each aquifer and confining layers.

d. Prediction of the sources of water to be extracted by the well and the drawdown of existing wells, springs, and surface water bodies that may be caused by pumping the proposed well. This prediction may be based on analytical or numerical models as determined by the Idaho Department of Water Resources permitting process.

e. Demonstration of the extent of the capture zone of the well, based on the well's design discharge and on aquifer geology, using estimates of hydraulic conductivity and storativity.

f. Description of potential sources of contamination including, but not limited to, sewers and sewage treatment/disposal facilities, highways, railroads, landfills, outcroppings of consolidated water-bearing formations, chemical facilities, waste disposal wells, and agricultural uses within five hundred (500) feet of the well site.

02.Location. In vulnerable settings, the Department may require engineering or hydrologic analysis to determine if the required setback distance is adequate to prevent contamination. Each well must be staked by the design engineer or licensed professional geologist prior to drilling and meet the following minimum distances:

Minimum Distances from a Public Water System Well
Frost free hydrant	5 feet
Property line	50 feet
Gravity wastewater line	50 feet
Any potential source of contamination	50 feet
Pressure wastewater line	100 feet
Class A Municipal Reclaimed Wastewater Pressure distribution line	50 feet
Individual home septic tank	100 feet
Individual home disposal field	100 feet
Individual home seepage pit	100 feet
Privies	100 feet
Livestock	50 feet
Drainfield - standard subsurface disposal module	100 feet
Absorption module - large soil absorption system	150 - 300 feet, see IDAPA 58.01.03
Canals, streams, ditches, lakes, ponds and tanks used to store non-potable substances	50 feet
Storm water facilities disposing storm water originating off the well lot	50 feet
Municipal or industrial wastewater treatment plant	500 feet
Reclamation and reuse of municipal and industrial wastewater sites	See IDAPA 58.01.17
Biosolids application site	1,000 feet

03.Construction Standards. In addition to meeting the requirements of these rules, all wells must be constructed in accordance with IDAPA 37.03.09, "Well Construction Standards Rules," and related rules and laws administered by the Idaho Department of Water Resources. All wells must comply with the drilling permit requirements of Section 42-235, Idaho Code.

a. Casing for steel pipe must meet the following requirements:

STEEL PIPE
	DIAMETER (inches)		THICKNESS (inches)	WEIGHT PER FOOT (pounds)
SIZE	External	Internal		Plain Ends (calculated)	With Threads and Couplings (nominal)
6 (id)	6.625	6.065	0.280	18.97	19.18
8	8.625	7.981	0.322	28.55	29.35
10	10.750	10.020	0.365	40.48	41.85
12	12.750	12.000	0.375	49.56	51.15
14 (od)	14.000	13.250	0.375	54.57	57.00
16	16.000	15.250	0.375	62.58
18	18.000	17.250	0.375	70.59
20	20.000	19.250	0.500	78.60
22	22.000	21.000	0.500	114.81
24	24.000	23.000	0.500	125.49
26	26.000	25.000	0.500	136.17
28	28.000	27.000	0.500	146.85
30	30.000	29.000	0.500	157.53
32	32.000	31.000	0.500	168.21
34	34.000	33.000	0.500	178.89
36	36.000	35.000	0.500	189.57

* id = inside diameter

* od = outside diameter

b. The use of plastic well casing for PWS wells may be considered on a case-by-case basis. Plastic casing must meet or exceed ASTM Standard F480, current edition, and ANSI/NSF Standard 61. Plastic casing must also meet the following requirements:

i. Have a minimum wall thickness equivalent to standard dimension ratio 21. However, diameters of 8 inches or greater or deep wells may require greater thickness to meet collapse strength requirements;

ii. Must not be used at sites where permeation by hydrocarbons or degradation may occur;

iii. Must be assembled using coupling or solvent welded joints. All coupling and solvents must meet ANSI/NSF Standard 14, ASTM F480, or similar requirements; and

iv. Must not be driven.

c. PWS wells must have no less than fifty-eight (58) feet of annular seal of not less than one and one-half (1¹/₂) inches thickness as measured from land surface to the bottom of the seal unless:

i. It can be demonstrated to the Department's satisfaction that there is a confining layer at lesser depth that is capable of preventing unwanted water from reaching the intake zone of the well; or

ii. The best and most practical aquifer at a particular site is less than fifty-eight (58) feet deep; or;

iii. The Department specifies a different annular seal depth based on local hydrologic conditions.

d. Specifications must include allowable tolerances for plumbness and alignment in accordance with AWWA Standards, incorporated by reference into these rules at Subsection 002.01, or as otherwise approved by the Department. If the well fails to meet these requirements, it may be accepted by the Department if it does not interfere with the installation or operation of the pump or uniform placement of grout.

e. Geological data must be collected at each pronounced change in formation and shall be recorded in the driller's log. Supplemental data includes, but is not limited to, accurate geographical location such as latitude and longitude or GIS coordinates, and other information on accurate records of drillhole diameters and depths, assembled order of size and length of casing, screens and liners, grouting depths, formations penetrated, and water levels.

f. The owner of each well must retain all records pertaining to each well until the well has been properly abandoned.

g. Wells with intake screens must:

i. Be constructed of materials resistant to damage by chemical action of groundwater or cleaning operations.

ii. Have openings based on sieve analysis of formation, of gravel pack materials, or both.

iii. Have sufficient length and diameter to provide adequate specific capacity and aperture entrance velocity not to exceed point one (0.1) feet per second, or as otherwise approved by the Department.

iv. Be installed so that the pumping water level remains above the screen under all operating conditions, or otherwise approved by the Department. Where a bottom plate or sump is utilized, it must be of the same material as the screen, or as otherwise approved by the Department. Where a washdown assembly, tailpipe or sump is used below the screen, it may be made of a different material than the screen.

h. Permanent well casing must be surrounded by a minimum of one and one-half (1 ¹/₂) inches of grout to the depth required by Subsection 510.03.b., or by the Rules of the Idaho Department of Water Resources, whichever is greater. All casing identified in plans and specifications as temporary casing must be removed prior to well completion.

i. Neat cement grout consisting of cement that conforms to AWWA Standard A-100, and water, with not more than six (6) gallons of water per ninety-four (94) pounds of cement, must be used for one and one-half (1 ¹/₂) inch annular space. Additives may be used to increase fluidity and are subject to approval by the Department and the Idaho Department of Water Resources on a case-by-case basis.

ii. Bentonite grout must have a solids content not less than twenty-five (25) percent by weight when mixed with water and be specifically manufactured for use in sealing of well casing. Bentonite grout shall not contain weighting agents to increase solids content. Bentonite grout must not be used above the water table. All bentonite grout must be installed by positive displacement from the bottom up through a tremmie or float shoe.

iii. Where a dry annular space is to be sealed, a minimum of two (2) inches on all sides of the casing will be required to place bentonite to depths not greater than one hundred (100) feet, using #8 mesh granular bentonite. All dry pour granular bentonite must be tagged at appropriate intervals to verify placement. If a bridge occurs, a tremmie pipe must be washed or jetted through the bridge to allow for pumping of grout. Bentonite chips must be of sufficient size to accommodate proper placement for the existing subsurface conditions.

iv. Dry granular bentonite used in wells where a dry annular space is to be sealed with depths greater than one hundred (100) feet will require an annulus of at least three (3) inches on all sides of the casing, or as approved by the Department and the Idaho Department of Water Resources. If a bridge occurs, a tremmie pipe must be washed or jetted through the bridge to allow for pumping of grout. Bentonite chips must be of sufficient size to accommodate proper placement for the existing subsurface conditions.

v. All chip bentonite seals installed through water must only be used in annular spaces of at least four (4) inches on all sides of the casing. If a bridge occurs, a tremmie pipe must be washed or jetted through the bridge to allow for pumping of grout. Bentonite chips must be of sufficient size to accommodate proper placement for the existing subsurface conditions. Chip bentonite seals installed through water must be:

(1) Installed in accordance with manufacturer's specifications; or

(2) Installed by pouring chips over a one-quarter (1/4) inch mesh screen for three-eighths (3/8) inch chips to remove fines to prevent bridging at the water table; or

(3) Installed using coated pellets to retard hydration if approved by the Department and the Idaho Department of Water Resources.

vi. Concrete may be approved on a case-by-case basis by the Department and the Idaho Department of Water Resources. Upon such approval, the approved method must use a six (6) sack minus one-half (1/2) inch Portland cement concrete and must be installed by positive displacement from the bottom up through a tremmie pipe.

04.Disinfection. All tools, bits, pipe, and other materials to be inserted in the borehole must be cleaned and disinfected in accordance with the Well Construction Standards and permitting requirements of the Idaho Department of Water Resources. This applies to new well construction and repair of existing wells.

05.Well Completion Report. Upon completion of a well, and prior to its use as a drinking water source, the following information and data must be submitted by the PWS to the Department. The well completion report must be submitted to the Department prior to or concurrent with the submittal of the preliminary engineering report for well house construction/modification. The well completion report must bear the imprint of an Idaho licensed professional engineer's or an Idaho licensed professional geologist's seal that is both signed and dated by the engineer or geologist:

a. A copy of all well logs;

b. Results of test pumping, as specified in Subsection 510.06;

c. As constructed plans showing at least the following:

i. Annular seal, including depth and sealant material used and method of application;

ii. Casing perforations, results of sieve analysis used in designing screens installed in sand or gravel aquifers, gravel packs; and

iii. Recommended pump location.

d. Other information as may be specified by the Department.

e. Sampling results for iron, manganese, corrosivity, and other secondary contaminants specified by the Department. Other monitoring requirements are specified in Subsections 510.05.e.i. through 510.05.e.iii.

i. Community systems must submit results of analysis for total coliform, inorganic chemical contaminants, organic chemicals, and radionuclide contaminants set forth in Subsections 050.01, 050.02, 050.05, 100.01, 100.03, 100.04, 100.05, and 100.06, unless analysis is waived pursuant to Subsection 100.07.

ii. Non-transient Non-community systems must submit results of analysis for total coliform and inorganic and organic chemical contaminants listed in Subsections 050.01, 050.02, 100.01, 100.03, 100.04, unless analysis is waived pursuant to Subsection 100.07.

iii. Transient Non-community systems must submit results of a total coliform, nitrite, and nitrate analysis listed in Subsections 050.01, 100.01 and 100.03.

06.Test Pumping. Upon completion of a groundwater source, test pumping must be conducted in accordance with the following procedures to meet the specified requirements:

a. The well must be test pumped at the desired yield (design capacity) of the well for at least twenty-four (24) consecutive hours after the drawdown trend has stabilized, as determined by the supervising engineer or geologist. Alternatively, the well may be pumped at a rate of one hundred fifty percent (150%) of the desired yield for at least six (6) continuous hours after the drawdown trend has stabilized, as determined by the supervising engineer or geologist. The field pumping equipment must be capable of maintaining a constant rate of discharge during the test. Discharge water must be piped an adequate distance to prevent recharge of the well during the test. If the well fails the test protocol, design of the PWS must be re-evaluated and submitted to the Department for approval.

b. Upon completion of well development, the well must be tested for sand production. Fifteen (15) minutes after the start of the test pumping (at or above the design production rate), the sand content of a new well may not be more than five (5) parts per million. Sand production must be measured by a centrifugal sand sampler or other means acceptable to the Department. If sand production exceeds five (5) ppm, the well must be screened gravel packed, or re-developed.

c. The following data must be provided:

i. Static water level and stabilized drawdown;

ii. Well yield in gpm and duration of the pump test, including a discussion of any discrepancy between the desired yield and the yield observed during the test;

iii. Water level in the well recorded at regular intervals during pumping;

iv. Profile of water level recovery from the pumping level projected to the original static water level.

v. Depth at which the test pump was positioned in the well;

vi. Test pump capacity and head characteristics;

vii. Sand production data.

viii. Results of analysis based on the drawdown and recovery test pertaining to aquifer properties, long term yield, and boundary conditions affecting drawdown.

d. The Department may allow the use of other pump test protocols that are generally accepted by engineering firms with specialized experience in well construction, by the well drilling industry, or as described in national standards (such as ANSI/AWWA A100), as long as the minimum data specified in Subsection 510.06.c. are provided. The Department welcomes more extensive data about the well, such as step-drawdown evaluations used in determining well capacity for test pumping purposes, zone of influence calculations, and any other information that may be of use in source protection activities or in routine PWS operations.

e. Where aquifer yield, sustainability, or water quality are questionable, the Department, at its discretion, may require additional site-specific investigations that include test well construction, long-term pumping tests, or other means to demonstrate that the aquifer yield is sufficient to meet the long-term water requirements of the project.

07.Conversion of Non-Public Water System Wells for Public Water System Use. Any existing well constructed for use other than as a PWS source may be considered for use as a PWS source on a case-by-case basis. The owner of such a well must demonstrate to the Department's satisfaction that the well site conforms to the requirements of Subsections 510.01, 510.02, and Section 512, the well is constructed in a manner that is protective of public health, and that both the quantity and quality of water produced by the well meet PWS standards set forth in these rules.

08.Monitoring Wells. If monitoring (observation) wells are used and are intended to remain in service after completion of the water supply well, the observation wells must be constructed in accordance with the requirements for permanent wells and be protected at the upper terminal to preclude entrance of foreign materials in accordance with the "Well Construction Standard Rules," IDAPA 37.03.09.

09.Well Abandonment. Well decommissioning (abandonment) must be performed in accordance with Department of Water Resources requirements set forth in IDAPA 37.03.09, "Well Construction Standard Rules.

Idaho Admin. Code r. 58.01.08.510

Effective July 1, 2024