10 CSR 23-3.090 - Drilling Areas

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PURPOSE: This rule sets construction standards in addition to 10 CSR 23-3.030 Standards for Construction of Water Wells. These additional standards apply to domestic and multifamily wells and vary by geographic area based on geologic, hydrologic, and/ or environmental factors (see Figure 3.1). It is the responsibility of the well installation contractor to determine in which drilling area a proposed well is located and associated construction requirements of that area.

(1) Area 1. This area encompasses portions of southwestern, central, east-central, and southeastern Missouri (see Figure 3.2).

(A) Bedrock wells.

1. A minimum of eighty feet (80') of casing shall be installed and extend a minimum of thirty feet (30') into solid bedrock. Example: If sixty feet (60') of residual material or broken rock is encountered during drilling above solid bedrock, then ninety feet (90') of casing will be installed.

2. Construct the borehole for domestic wells a minimum of two inches (2") larger than the casing being installed.

3. Install new casing pursuant to 10 CSR 23-3.030(1)(A).

4. Grouting Requirements.

A. The lowermost thirty feet (30') of casing shall be grouted.

B. Grouting materials and methods shall be followed pursuant to 10 CSR 23-3.030(1)(C).

C. The annular space above the grouted interval shall be filled with clean fill.

(B) Unconsolidated material wells.

1. A minimum of twenty feet (20') of casing shall be installed above the screened or perforated interval.

2. Construct the borehole for domestic wells a minimum of four inches (4"|) larger in diameter than the casing being installed.

3. Install new casing pursuant to 10 CSR 23-3.030(1)(A).

4. Grouting Requirements.

A. The upper twenty feet (20') of casing shall be grouted.

B. Grouting methods and materials shall be followed pursuant to 10 CSR 23-3.030(1)(C).

C. A chlorinated gravel pack may be placed into the annular space or native materials may be allowed to collapse against the well screen or perforated interval.

(2) Area 2. This area encompasses west-central Missouri and is delineated separately because the bedrock has the potential to produce groundwater with high dissolved solids compared to other areas of the state (see Figure 3.3).

(A) Bedrock wells.

1. A minimum of forty feet (40') of casing shall be installed and extend a minimum of fifteen feet (15') into solid bedrock.

2. Construct the borehole for domestic wells a minimum of two inches (2") larger than the casing being installed.

3. Install new casing pursuant to 10 CSR 23-3.030(1)(A).

4. Grouting Requirements.

A. The lowermost thirty feet (30') of casing shall be grouted.

B. Grouting materials and methods shall be followed pursuant to 10 CSR 23-3.030(1)(C).

C. The annular space above the grouted interval shall be filled with clean fill.

(B) Unconsolidated material wells.

1. A minimum of twenty feet (20') of casing shall be installed above the screened or perforated interval.

2. Construct the borehole for domestic wells a minimum of four inches (4") larger in diameter than the casing being installed.

3. Install new casing pursuant to 10 CSR 23-3.030(1)(A).

4. Grouting Requirements.

A. The upper twenty feet (20') of casing shall be grouted.

B. Grouting materials and methods shall be followed pursuant to 10 CSR 23-3.030(1)(C).

C. A chlorinated gravel pack may be placed into the annular space or native materials may be allowed to collapse against the well screen or perforated interval.

(3) Area 3. This area encompasses northwestern and northcentral Missouri and is delineated separately because glacial till overlies bedrock that has a higher likelihood of producing groundwater with high dissolved solids compared to other areas of the state (see Figure 3.4).

(A) Bedrock wells.

1. A minimum of forty feet (40') of casing shall be installed and extend a minimum of fifteen feet (15') into solid bedrock.

2. Construct the borehole for domestic wells a minimum of two inches (2") larger than the casing being installed.

3. Install new casing pursuant to 10 CSR 23-3.030(1)(A).

4. Grouting Requirements.

A. The lowermost thirty feet (30') of casing shall be grouted.

B. Grouting materials and methods shall be followed pursuant to 10 CSR 23-3.030(1)(C).

C. The annular space above the grouted interval shall be filled with clean fill.

5. Shallow Bedrock Well - If usable quantities of water are not expected to be available in deeper bedrock horizons one (1) of the following construction methods may be used.

A. Method 1.

(I) A minimum of forty feet (40') of casing shall be installed pursuant to 10 CSR 23-3.030(1)(A).

(II) A minimum of one foot (1') of casing shall extend into solid bedrock.

(III) Construct the borehole for domestic wells a minimum of two inches (2" larger than the casing being installed.

(IV) The lower thirty feet (30') of casing shall be grouted.

(V) Grouting materials and methods shall be followed pursuant to 10 CSR 23-3.030(1)(C).

(VI) The annular space above the grouted interval shall be filled with clean fill.

B. Method 2.

(I) The casing shall be installed full-length pursuant to 10 CSR 23-3.030(1)(A) and perforated below twenty (20') feet across the producing horizon.

(II) Construct the borehole for domestic wells two inches (2") larger than the casing being installed with the upper twenty feet (20') reamed out to four inches (4") larger than the casing being installed.

(III) The upper twenty feet (20') of annular space shall be grouted and the remainder of the borehole below the grout shall be gravel packed if a packer is not installed.

6. All construction requirements pursuant to 10 CSR 233.030 shall be met except as stated in 10 CSR 23-3.090(3)(A) 5.

(B) Unconsolidated material wells and glacial drift wells.

1. A minimum of twenty feet (20') of casing shall be installed above the screened or perforated interval.

2. Construct the borehole for domestic wells a minimum of four inches (4") larger in diameter than the casing being installed.

3. Grouting Requirements.

A. The upper twenty feet (20') of casing shall be grouted.

B. Grouting materials and methods shall be followed pursuant to 10 CSR 23-3.030(1)(C).

C. A chlorinated gravel pack may be placed into the annular space or native materials may be allowed to collapse against the screen or perforated interval.

(4) Area 4. This area encompasses northeastern Missouri and is delineated separately because glacial till of low permeability overlies bedrock that has a higher likelihood of producing groundwater with high dissolved solids compared to other areas of the state (see Figure 3.5).

(A) Bedrock wells.

1. A minimum of forty feet (40') of casing shall be installed and extend a minimum of fifteen feet (15') into bedrock.

2. Construct the borehole for domestic wells a minimum of two inches (2") larger than the casing being installed.

3. Install new casing pursuant to 10 CSR 23-3.030(1)(A).

4. Grouting Requirements.

A. The lowermost thirty feet (30') of casing shall be grouted.

B. Grouting materials and methods shall be followed pursuant to 10 CSR 23-3.030(1)(C).

C. The annular space above the grouted interval shall be filled with clean fill.

5. Shallow bedrock wells - If usable quantities of water are not expected to be available in deeper bedrock horizons the following construction method may be used.

A. Method 1.

(I) A minimum of forty feet (40') of casing shall be installed pursuant to 10 CSR 23-3.030(1)(A).

(II) A minimum of one foot (1') of casing shall extend into solid bedrock.

(III) Construct the borehole for domestic wells a minimum of two inches (2") larger than the casing being installed.

(IV) The lower thirty feet (30') of casing shall be grouted.

(V) Grouting materials and methods shall be followed pursuant to 10 CSR 23-3.030(1)(C).

(VI) The annular space above the grouted interval shall be filled with clean fill.

6. All construction requirements pursuant to 10 CSR 233.030 shall be met except as stated in 10 CSR 23-3.090(4)(A) 5.

(B) Unconsolidated material wells and glacial drift wells.

1. A minimum of twenty feet (20') of casing shall be installed above the screened or perforated interval.

2. Construct the borehole for domestic wells a minimum of four inches (4") larger in diameter than the casing being installed.

3. Grouting Requirements.

A. The upper twenty feet (20') of casing shall be grouted.

B. Grouting materials and methods shall be followed pursuant to 10 CSR 23-3.030(1)(C).

C. A chlorinated gravel pack may be placed into the annular space or native materials may be allowed to collapse against the screen or perforated interval.

(5) Area 5. This area encompasses the Missouri and Mississippi River floodplains and is delineated separately because the uppermost aquifer consists of unconsolidated alluvium (see Figure 3.6).

(A) Bedrock wells.

1. A minimum of eighty feet (80') of casing shall extend a minimum of thirty feet (30') into bedrock.

2. Construct the borehole for domestic wells a minimum of two inches (2") larger than the casing being installed.

3. Install new casing pursuant to 10 CSR 23-3.030(1)(A).

4. The lowermost thirty feet (30') of casing shall be grouted pursuant to 10 CSR 23-3.030(1)(C). The annular space above the grouted interval shall be filled with clean fill.

(B) Unconsolidated material wells.

1. A minimum of twenty feet (20') of casing shall be installed above the screened or perforated interval.

2. Construct the borehole for domestic wells a minimum of four inches (4") larger than the casing diameter installed. Unconsolidated material wells that have a casing diameter less than four inches (<4") in diameter are exempt from these rules.

3. The upper twenty feet (20') of casing shall be grouted pursuant to 10 CSR 23-3.030(1)(C).

4. A chlorinated gravel pack may be placed into the annular space adjacent to the well screen or native materials may be allowed to collapse against the screen or perforated interval.

5. All construction requirements pursuant to 10 CSR 233.030 shall be met except as stated in 10 CSR 23-3.090(5)(B) 2. and 3.

(6) Area 6. This area encompasses the St. Francois Mountains and is delineated separately because igneous bedrock, which has low permeability, occurs close to the ground surface (Figure 3.7).

(A) Bedrock wells.

1. Bedrock wells where granite is less than one hundred feet (<100') below the surface.

A. A minimum of forty feet (40') of casing shall be installed and extend a minimum of fifteen feet (15') into solid bedrock. Example: If sixty feet (60') of residual material or broken rock is encountered during drilling above solid bedrock, then seventy-five feet (75') of casing shall be installed.

B. Construct the borehole for domestic wells a minimum of two inches (2") larger than the casing being installed.

C. Install new casing pursuant to 10 CSR 23-3.030(1)(A).

D. The lowermost thirty feet (30') of casing shall be grouted. The annular space above the grouted interval shall be filled with clean fill.

E. Grouting materials and methods shall be followed pursuant to 10 CSR 23-3.030(1)(C).

2. Bedrock wells where granite is one hundred feet or more (>=100') below the surface.

A. A minimum of eighty feet (80') of casing shall be installed and shall extend a minimum of thirty feet (30') into solid bedrock.

B. Construct the borehole for domestic wells a minimum of two inches (2") larger than the casing being installed.

C. Install new casing pursuant to 10 CSR 23-3.030(1)(A).

D. The lowermost thirty feet (30') of casing shall be grouted. The annular space above the grouted interval shall be filled with clean fill.

E. Grouting materials and methods shall be followed pursuant to 10 CSR 23-3.030(1)(C).

(B) Unconsolidated material wells.

1. A minimum of twenty feet (20') of casing shall be installed above the screened or perforated interval.

2. Construct the borehole for domestic wells a minimum of four inches (4") larger in diameter than the casing being installed.

3. Install new casing pursuant to 10 CSR 23-3.030(1)(A).

4. The upper twenty feet (20') of casing shall be grouted.

5. Grouting materials and methods shall be followed pursuant to 10 CSR 23-3.030(1)(C).

6. A chlorinated gravel pack may be placed into the annular space or native materials may be allowed to collapse against the well screen or perforated interval.

(7) Area 7. This area encompasses Osage, Gasconade, Maries, and parts of Phelps, Crawford, and Franklin counties and is delineated separately because it is overlain in part by Pennsylvanian-aged bedrock that is capable of producing groundwater with high dissolved solids (see Figure 3.2).

(A) Bedrock Wells.

2. In areas where Pennsylvanian-age strata (shale, sandstone, and/or clay) are present, a minimum of one hundred fifty feet (150') of casing shall be installed and extend at least thirty feet (30') below the Pennsylvanian age strata (shale, sandstone, and/or clay).

3. Construct the borehole for domestic wells a minimum of two inches (2") larger than the casing being installed.

4. Install new casing pursuant to 10 CSR 23-3.030(1)(A).

5. Grouting Requirements.

A. The lowermost thirty feet (30') of casing shall be grouted.

B. Grouting materials and methods shall be followed pursuant to 10 CSR 23-3.030(1)(C).

C. The annular space above the grouted interval shall be filled with clean fill.

(B) Unconsolidated material wells.

1. A minimum of twenty feet (20') of casing shall be installed above the screened or perforated interval.

2. Construct the borehole for domestic wells a minimum of four inches (4") larger in diameter than the casing being installed.

3. Install new casing pursuant to 10 CSR 23-3.030(1)(A).

4. Grouting Requirements.

A. The upper twenty feet (20') of casing shall be grouted.

B. Grouting materials and methods shall be followed pursuant to 10 CSR 23-3.030(1)(C).

C. A chlorinated gravel pack may be placed into the annular space or native materials may be allowed to collapse against the well screen or perforated interval.

(8) Area 8. This area encompasses a one-quarter (1/4) mile buffer from the twenty foot (20') water depth contour line of major lakes in Missouri (see Figure 3.2).

(A) The major lakes include -

1. Truman;

2. Stockton;

3. Table Rock;

4. Bull Shoals;

5. Lake of the Ozarks;

6. Pomme de Terre;

7. Norfork; and

8. Clearwater.

(B) Bedrock Wells.

1. Casing shall be installed fifty feet (50') below the deepest point of the lake within one-quarter (1/4) mile radius of the well location. Casing shall not be less than the minimum requirements outlined in Drill Area 1 (10 CSR 23-3.090(1)) a minimum of eighty feet (80') and extend thirty feet (30') into bedrock. Formula: well site elevation (feet) - deepest lake elevation within one-quarter (1/4) mile (feet) + fifty feet (50') = casing depth. Example: 1000' (well site elevation) - 850' (deepest lake elevation within one-quarter (1/4) mile) + 50' = 200' casing depth.

2. A casing point request may be submitted to the department prior to drilling in Drill Area 8.

3. Construct the borehole for domestic wells a minimum of two inches (2") larger than the casing being installed.

4. Install new casing pursuant to 10 CSR 23-3.030(1)(A).

5. When plastic casing is used, liner shall not be used in lieu of casing.

6. When steel casing is used, and the minimum casing depth cannot be achieved due to geologic reasons, casing shall be installed to a minimum of eighty feet (80') extending a minimum of thirty feet (30') into bedrock and a liner used to achieve the remaining casing depth provided the following requirements are met:

A. Have a minimum annular space of one-half inch (1/2");

B. Secure packers at or below the bottom of the minimum casing depth;

C. Have the top of the liner extend to within twenty feet (20') of the top of casing;

D. Have packers placed a maximum of ten feet (10') apart;

E. Grout pursuant to 10 CSR 23-3.090(8)(B) 7. using the gravity or tremie grouting method using cement slurry or coated bentonite pellets; and

F. Liner specifications shall be followed pursuant to 10 CSR 23-3.080(1), (2), (4), and (5).

7. Grouting Requirements.

A. The lowermost thirty feet (30') of casing shall be grouted.

B. Grouting materials and methods shall be followed pursuant to 10 CSR 23-3.030(1)(C).

C. The annular space above the grouted interval shall be filled with clean fill.

(9) Area 9. This area encompasses Greene and parts of Christian County where rapid urbanization is occurring in a sensitive geologic and hydrologic setting. The upper aquifer (Springfield Plateau Aquifer) and lower aquifer (Ozark Aquifer) are inconstantly separated by low-permeability bedrock (Ozark Confining Unit). This low-permeability bedrock generally limits migration of groundwater and any associated contamination from the upper aquifer to the lower aquifer (see Figure 3.2).

(A) Bedrock Wells.

1. The casing shall be installed a minimum of ten feet (10') below the Ozark Confining Unit.

2. A casing point request may be submitted to the department prior to drilling in Drill Area 9.

3. Construct the borehole for domestic wells a minimum of two inches (2") larger than the casing being installed.

4. Install new casing pursuant to 10 CSR 23-3.030(1)(A).

5. If plastic casing is used, construct the borehole a minimum of four inches (4") larger than the casing being installed. When plastic casing is used, liner shall not be used in lieu of casing.

6. When steel casing is used and the minimum casing depth cannot be achieved due to geologic reasons, casing shall be installed to a minimum of eighty feet (80') extending a minimum of thirty feet (30') into bedrock and a liner used to achieve the remaining casing depth provided the following requirements are met:

A. Have a minimum annular space of one-half inch (1/2");

B. Secure packers at or below the bottom of the Ozark Confining Unit pursuant to 10 CSR 23-3.090(9)(A) 1.;

C. Have the top of the liner extend to within twenty feet (20') of the top of casing;

D. Have packers placed a maximum of ten feet (10') apart;

E. Grout pursuant to 10 CSR 23-3.090(9)(A) 7. using the gravity or tremie grouting method using cement slurry or coated bentonite pellets; and

F. Liner specifications shall be followed pursuant to 10 CSR 23-3.080(1), (2), (4), and (5).

7. Grouting Requirements.

A. The Ozark Confining Unit shall be grouted from ten feet (10') below the Ozark Confining Unit to the top of the Ozark Confining Unit and at a minimum the lowermost thirty feet (30') of casing shall be grouted.

B. When the casing extends more than ten feet (10') below the bottom of the Ozark Confining Unit, more than thirty feet (30') of grout will be required to seal off the Ozark Confining Unit.

C. Grouting materials and methods shall be followed pursuant to 10 CSR 23-3.030(1)(C).

D. The annular space above the grouted interval shall be filled with clean fill.

(B) Unconsolidated material wells. The unconsolidated requirements for Drill Area 1 apply.

(10) Area 10. This area encompasses a portion of southeastern Missouri and is composed of deeply weathered and highly fractured bedrock where openings may be filled with mud extending deep into bedrock (see Figure 3.8).

(A) Bedrock Wells.

1. A minimum of eighty feet (80') of casing shall be installed and extend a minimum of fifteen feet (15') into solid bedrock. Example: If eighty feet (80') of residual material or broken rock is encountered during drilling above solid bedrock, then ninety-five feet (95') of casing shall be installed. If solid bedrock is not encountered within one hundred and fifty feet (150') the contractor may consult the department for further instructions regarding a variance or install casing into deeper solid bedrock.

2. Construct the borehole for domestic wells a minimum of two inches (2") larger than the casing being installed.

3. Install new casing pursuant to 10 CSR 23-3.030(1)(A).

4. Grouting Requirements.

A. If casing is driven, see 10 CSR 23-3.030(1)(D) for liner and grouting requirements.

B. If casing is not driven, the lowermost thirty feet (30') of casing shall be grouted.

(I) Grouting materials and methods shall be followed pursuant to 10 CSR 23-3.030(1)(C).

(II) The annular space above the grouted interval shall be filled with clean fill.

(B) If unconsolidated material wells are drilled in Area 10, Drill Area 1 requirements for unconsolidated wells apply.

(11) Area 11. This area encompasses Newton and Jasper County and is delineated separately due to the contamination of portions of the upper aquifer by one (1) or more of the following: lead, cadmium, chlorinated volatile organic compounds (VOCs) including trichloroethylene (TCE), TCE degradation products, or other contaminants pursuant to 10 CSR 60-4. The upper aquifer (Springfield Plateau Aquifer) and lower aquifer (Ozark Aquifer) are inconstantly separated by low-permeability bedrock (Ozark Confining Unit). This low-permeability bedrock generally limits migration of groundwater and any associated contamination from the upper aquifer to the lower aquifer (see Figure 3.2).

(A) Bedrock Wells.

1. Wells outside of Impact Areas may be installed in the upper aquifer provided they do not penetrate the Ozark Confining Unit; or wells may be installed and cased/sealed through the Ozark Confining Unit and open to only the lower aquifer.

2. New upper aquifer wells outside of Impact Areas.

A. Total depth of the well shall not penetrate the Ozark Confining Unit.

B. A minimum of eighty feet (80') of casing shall be installed and extend a minimum of thirty feet (30') into solid bedrock. Example: If sixty feet (60') of residual material or broken rock is encountered during drilling above solid bedrock, then ninety feet (90') of casing will be installed.

C. Construct the borehole for domestic wells a minimum of two inches (2") larger than the casing being installed.

D. Install new casing pursuant to 10 CSR 23-3.030(1)(A).

E. Grouting Requirements.

(I) The lowermost thirty feet (30') of casing shall be grouted.

(II) Grouting materials and methods shall be followed pursuant to 10 CSR 23-3.030(1)(C).

(III) The annular space above the grouted interval shall be filled with clean fill.

F. New upper aquifer wells shall follow sampling requirements pursuant to 10 CSR 23-3.090(11)(A) 6.

3. New lower aquifer wells outside of the Impact Areas.

A. The casing shall be installed a minimum of ten feet (10') below the Ozark Confining Unit.

B. A casing point request may be submitted to the department prior to drilling in Drill Area 11.

C. Install new casing pursuant to 10 CSR 23-3.030(1)(A).

D. If steel casing is used, construct the borehole a minimum of two inches (2") larger than the casing being installed.

E. When steel casing is used and the minimum casing depth cannot be achieved due to geologic reasons, casing shall be installed to a minimum of eighty feet (80') extending thirty feet (30') into bedrock with the lowermost thirty feet (30') of casing grouted pursuant to 10 CSR 23-3.090(11) (A) 3.E. and a liner used to achieve the remaining casing depth provided the following requirements are met:

(I) Have a minimum annular space of one-half inch (1/2");

(II) Secure packers at or below the bottom of the Ozark Confining Unit pursuant to 10 CSR 23-3.090(11)(A) 4.A.;

(III) Have the top of the liner extend to within twenty feet (20') of the top of casing;

(IV) Have packers placed a maximum of ten feet (10') apart;

(V) Grout using methods and materials pursuant to 10 CSR 23-3.090(11)(A) 4.G.(II) and (III) from the top packer to extend ten feet (10') inside the casing using the gravity or tremie grouting method using cement slurry or coated bentonite pellets; and

(VI) Liner specifications shall be followed pursuant to 10 CSR 23-3.080(1), (2), (4), and (5).

F. If plastic casing is used, construct the borehole a minimum of four inches (4") larger than the casing being installed. When plastic casing is used, liner shall not be used in lieu of casing.

G. Grouting Requirements.

(I) Full-length grout is required.

(II) Grouting methods shall be Tremie Pressure, Pressure, or Positive Displacement pursuant to 10 CSR 23-3.030(1)(C) 1.C., 10 CSR 23-3.030(1)(C) 1.D., and 10 CSR 23-3.030(1) (C) 1.F.

(III) Grouting materials shall be cement slurry or high-solids bentonite slurry.

(IV) Wells with eighty feet (80') of casing may use grouting materials and methods pursuant to 10 CSR 23-3.030(1) (C).

H. All construction requirements pursuant to 10 CSR 23-3.030 shall be met except as provided in 10 CSR 23-3.090(11) (A) 4.G.

4. Major reconstruction of wells in Area 11 that involve penetrating the Ozark Confining Unit require advanced written approval from the department.

5. Sampling requirements for new upper aquifer wells.

A. Water sampling and analysis shall be performed for lead and cadmium. Additionally, for new wells constructed in adjoining quarter-sections, including corner points, of TCE impact areas, water sampling and analysis shall also be performed for TCE and its degradation products. Wells will not be certified until all sampling has been completed and results received by the department.

B. Permitted pump installers and owners who self-install pumps are responsible for ensuring sampling is completed according to laboratory sampling protocol and submitting sample results within sixty (60) days of pump installation.

C. The laboratory that analyzes the sample shall be certified by the EPA or the department for such analyses.

D. Prior to sampling, run water from the tap closest to the well at full capacity for ten (10) minutes then reduce flow for sample collection.

E. All new upper aquifer wells shall be constructed with a sampling port or tap within twenty feet (20') of the wellhead.

F. If an upper aquifer well contains levels of lead, cadmium, TCE or its degradation products that are above the respective Maximum Contaminant Level (MCL) or Action Level (AL), the well may -

(I) Be plugged full-length with approved grout material; or

(II) Be reconstructed and sealed through the Ozark Confining Unit pursuant to 10 CSR 23-3.090(11)(A) 5.

6. Well installation in Impact Areas.

A. The casing shall be installed a minimum of ten feet (10') below the Ozark Confining Unit.

B. A casing point request may be submitted to the department prior to drilling in Drill Area 11.

C. Install new casing pursuant to 10 CSR 23-3.030(1)(A). A liner shall not be used in lieu of casing.

D. Construct the borehole to be a minimum of four inches (4") larger than the casing being installed.

E. Grouting Requirements.

(I) Full-length grout is required.

(II) Grouting methods shall be Tremie Pressure, Pressure, or Positive Displacement pursuant to 10 CSR 23-3.030(1)(C) 1.C., 10 CSR 23-3.030(1)(C) 1.D., and 10 CSR 23-3.030(1) (C) 1.F.

(III) Grouting materials shall be cement slurry or high-solids bentonite slurry.

(B) Unconsolidated Material Wells.

1. If unconsolidated material wells are drilled in Area 11 outside of Impact areas, Drill Area 1 requirements for unconsolidated wells apply.

2. Advanced written approval from the department is required if unconsolidated material wells are drilled in Impact Areas.

(12) Area 12. This area encompasses portions of Franklin County within and south of the city of New Haven and is delineated separately due to the contamination of portions of the aquifer by one (1) or more of the following known contaminants: tetrachloroethylene or perchloroethylene (PCE), trichloroethylene (TCE), TCE degradation products, and may include other contaminants pursuant to 10 CSR 60-4. It is necessary to implement more stringent well construction standards for new wells that are drilled into the aquifer and to limit the deepening of existing upper aquifer wells (see Figure 3.9).

(A) New Wells.

1. Prior written approval and construction specifications shall be obtained from the department for any new wells constructed in Area 12.

2. Water sampling for contaminants will be required pursuant to 10 CSR 23-3.090(12)(C).

3. Drilling shall cease and the department is to be notified immediately if PCE or TCE is encountered above the maximum contaminant level (MCL) or action level (AL). The department will determine further action.

(B) Reconstruction of Existing Wells.

1. Prior written approval and reconstruction specifications shall be obtained from the department for any reconstructed wells in Area 12.

2. Water sampling for contaminants will be required pursuant to 10 CSR 23-3.090(12)(C). Wells that are contaminated at levels exceeding maximum contaminant levels (MCLs) and/or action levels (ALs) shall not be deepened.

3. Drilling shall cease and the department is to be notified immediately if PCE or TCE is encountered above the maximum contaminant level (MCL) or action level (AL) during reconstruction. The department will determine further action.

1. Groundwater sampling for contaminants is required according to laboratory sampling protocol for any new well or reconstruction and methods will be established on a case-by-case basis by the department.

2. The well installation contractor is responsible for ensuring sampling is conducted throughout the drilling process and results submitted in accordance with pre-approved department sampling methods. Final sampling of the well shall be completed by the pump installation contractor within sixty (60) days of pump installation. Wells will not be certified or registered until all sampling has been completed.

3. Sampling and analysis shall be performed for known contaminants listed in 10 CSR 23-3.090(12) and other contaminants as determined by the department.

4. The laboratory that analyzes the sample shall be certified by the EPA or the department for analyses being requested.

5. All new and deepened wells shall be constructed with a sampling port or tap at or before the pressure tank within twenty feet (20') of the wellhead.

(D) Plugging.

1. Wells shall be plugged full length using bentonite slurry or cement grout via one of the tremie methods.

2. All plugging requirements in 10 CSR 23-3.110 shall be met except as required in 10 CSR 23-3.090(12)(D).

(E) All drilling-derived fluids, displaced water, and solid materials shall be containerized and sampled before disposal in accordance with federal, state, and local regulations based on analytical results.

(F) Any completed (new or reconstructed) well in which PCE and/or TCE is encountered at levels above MCL and/or AL shall be plugged full-length pursuant to 10 CSR 23-3.090(12)(D).

(13) Area 13. This area encompasses portions of St. Charles County west of the city of Weldon Spring and is delineated separately due to contamination of portions of the aquifer by one (1) or more of the following known contaminants listed by source in Table 3.10. In this area it is necessary to implement more stringent well construction standards for new wells that are drilled into the aquifer and to limit the deepening of existing upper aquifer wells (see Figure 3.10).

Table 3.10. Known contaminants of Drill Area 13 by source.

Source	Known Contaminants¹
U.S. Army	2,4,6-TNT, 2,4-DNT, 2,6-DNT, dinitrobenzene (1,3-DNB), nitrobenzene (NB), orthonitrotoluene (o-NT), metanitrotoluene (m-NT), paranitrotoluene (p-NT)
Department of Energy Main Site	2,4,6-TNT, 2,4-DNT, 2,6-DNT, dinitrobenzene (1,3-DNB), nitrobenzene (NB), nitrate, uranium, and trichloroethylene (TCE)
Department of Energy Quarry	uranium and 2,4-DNT

¹May also include other contaminants pursuant to 10 CSR 60-4.

(A) New Wells.

1. Prior written approval and construction specifications shall be obtained from the department for any wells constructed in Area 13.

2. Water sampling for contaminants will be required pursuant to 10 CSR 23-3.090(13)(C).

3. Drilling shall cease and the department is to be notified immediately if contaminants listed in Table 3.15 or other contaminants pursuant to 10 CSR 60-4 are encountered at levels above the maximum contaminant level (MCL), action level (AL), remedial goals stated in the Record of Decisions, and/or the risk-based value(s) calculated in the most recent site five- (5-) year review. The department will determine further action.

(B) Reconstruction of Existing Wells.

1. Prior written approval and construction specifications shall be obtained from the department for any reconstructed wells in Area 13.

2. Groundwater sampling for contaminants listed in Table 3.15 or other contaminants pursuant to 10 CSR 60-4 will be required in advance of any deepening. Wells that are contaminated at levels exceeding maximum contaminant level (MCL), action level (AL), remedial goals stated in the Record of Decisions, and/or the riskbased value(s) calculated in the most recent site five- (5-) year review shall not be deepened.

3. Any well approved to be deepened which encounters contaminants listed in Table 3.15 or other contaminants pursuant to 10 CSR 60-4 at levels above maximum contaminant level (MCL), action level (AL), remedial goals stated in the Record of Decisions, and/or the risk-based value(s) calculated in the most recent site five- (5-) year review, drilling shall cease and the department shall be notified immediately. The department will determine further action.

3. Sampling and analysis shall be performed for contaminants listed in Table 3.15.

4. The laboratory that analyzes the sample shall be certified by the EPA or the department for such analyses.

5. All new and deepened wells shall be constructed with a sampling port or tap at or before the pressure tank within twenty feet (20') of the wellhead.

(D) Plugging.

1. Wells shall be plugged full length using bentonite slurry or cement grout via one (1) of the tremie methods.

2. All plugging requirements in 10 CSR 23-3.110 shall be met except as required in 10 CSR 23-3.090(13)(D).

(F) Any completed (new or reconstructed) well in which contaminants listed in Table 3.15 or other contaminants pursuant to 10 CSR 60-4 are encountered at levels above the maximum contaminant level (MCL), action level (AL), remedial goals stated in the Record of Decisions, and/or the risk-based value(s) calculated in the most recent site five- (5-) year review shall be plugged full-length (10 CSR 23-3.090(13)(D)) or with approval from the department the well owner may be allowed to use the well provided groundwater quality will not be degraded further.

(G) Notwithstanding these provisions, the federal government does not waive its rights and authority under federal law, regulations, or executive order within the boundaries and applicable jurisdiction of federal property.

Table 3.10 AU Drilling Areas (Bedrock Water Wells). Minimum Number of Bags of Grout Required in Annular Space (Ann.) or Open Hole (O.H.) for Sealing Casing with a Minimum Grout Seal of Thirty Feet (30').

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Table 3.11 All Drilling Areas (Unconsolidated Water Wells). Minimum Number of Bags of Grout Required in Annular Space (Ann.) or Open Hole (O.H.) for Sealing Casing with a Minimum Upper Grout Seal of Twenty Feet (20').

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Table 3.12 Drilling Areas 3 and 4 (Bedrock or Shallow Bedrock Wells Method I Using Five and One-half Inch (5 1/2'') Casing Diameter). Minimum Number of Bags of Grout Required in Annular Space (Ann.) or Open Hole (O.H.) for Sealing Casing with a Minimum Grout Seal of Thirty Feet (30').

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Table 3.13 Drilling Areas 3 and 4 (Unconsolidated or Shallow Bedrock Water Wells Method 2 Using Five and One-half Inch (5 1/2") Casing Diameter), Minimum Number of Bags of Grout Required in the Annular Space (Ann.) or Open Hole (O.H.) for Sealing Casing for with a Minimum Upper Grout Seal of Twenty (20').

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Table 3.14 Drill Area 5 (Unconsolidated Water Wells Using Four and One-half Inch (4 1/2") Casing Diameter). Minimum Number of Bags of Grout Required in Annular Space (Ann,) or Open Hole (O.H.) for Sealing Casing with a Minimum Upper Grout Seal of Twenty Feet (20').

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Notes

10 CSR 23-3.090

AUTHORITY: sections 256.606 and 256.626, RSMo 2016.* Original rule filed April 2, 1987, effective July 27, 1987. Emergency amend ment filed Nov. 16, 1993, effective Dec. 11, 1993, expired April 9, 1994. Amended: Filed Aug. 17, 1993, effective March 10, 1994. Amended: Filed June 27, 2018, effective Feb. 28, 2019. Amended: Filed March 20, 2024, effective Nov. 30, 2024.

AUTHORITY: sections 256.606 and 256.626, RSMo Supp. 1991.* Original rule filed April 2, 1987, effective 7/27/1987. Emergency amendment filed Nov. 16, 1993, effective 12/11/1993, expired 4/9/1994. Amended: Filed Aug. 17, 1993, effective 3/10/1994. Amended by Missouri Register January 15, 2019/Volume 44, Number 2, effective 2/28/2019 Amended by Missouri Register October 1, 2024/volume 49, Number 19, effective 11/30/2024.

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