N.M. Code R. § 20.7.3.302
A. On-site liquid waste systems shall be located to meet setback distances, in feet, specified in the following Table 302.1. Setback distances apply to any part of the on-site liquid waste system.
Table 302.1: Minimum setback and clearance requirements
From: To: Building Sewer Treatment Unit* Disposal Field Seepage Pit Property lines clear 5 ft. 5 ft. 8 ft. Building or structure 2 ft. 5 ft. 8 ft. 8 ft. Distribution box -- -- 5 ft. 5 ft. Disposal field -- 10 ft.***** 4 ft**** 10 ft. Seepage pit -- 10 ft. 10 ft. 12 ft. Drinking water line******: - private 1 ft. 10 ft. 10 ft. 10 ft. - public 10 ft. 10 ft. 10 ft. 10 ft. Drinking water source/well: - private 50 ft. 50 ft. 100 ft. 100 ft. - public 50 ft. 100 ft. 200 ft. 200 ft. Irrigation well 50 ft. 50 ft. 100 ft. 100 ft. Lined canals -- 10 ft.** 10 ft.** 10 ft.** Unlined canals, drainage ditches -- 15 ft.** 25 ft.** 25 ft.** Arroyos -- 15 ft.** 25 ft.** 25 ft.** Other watercourses, Waters of the state -- 50 ft. 100 ft. 100 ft. Retention/detention area or flood irrigation areas -- 15 ft. 15 ft. 15 ft. Seasonal high water table, bedrock and other impervious layers*** -- -- 4 ft. to bottom of system 4 ft. to bottom of system
From: To:
Building Sewer
Treatment Unit*
Disposal Field
Seepage Pit
Property lines
clear
5 ft.
5 ft.
8 ft.
Building or structure
2 ft.
5 ft.
8 ft.
8 ft.
Distribution box
--
--
5 ft.
5 ft.
Disposal field
--
10 ft.*****
4 ft****
10 ft.
Seepage pit
--
10 ft.
10 ft.
12 ft.
Drinking water line******:
- private
1 ft.
10 ft.
10 ft.
10 ft.
- public
10 ft.
10 ft.
10 ft.
10 ft.
Drinking water source/well:
- private
50 ft.
50 ft.
100 ft.
100 ft.
- public
50 ft.
100 ft.
200 ft.
200 ft.
Irrigation well
50 ft.
50 ft.
100 ft.
100 ft.
Lined canals
--
10 ft.**
10 ft.**
10 ft.**
Unlined canals, drainage ditches
--
15 ft.**
25 ft.**
25 ft.**
Arroyos
--
15 ft.**
25 ft.**
25 ft.**
Other watercourses,
Waters of the state
--
50 ft.
100 ft.
100 ft.
Retention/detention area or flood irrigation areas
--
15 ft.
15 ft.
15 ft.
Seasonal high water table, bedrock and other impervious layers***
--
--
4 ft. to bottom of system
4 ft. to bottom of system
(1) * Applies to privy pits, enclosed systems, other liquid waste treatment units.
(2) ** Plus depth of channel.
(3) *** Unlined privy pits shall provide clearance of at least four feet.
(4) **** Plus two feet for each additional foot of depth below the invert of the distribution pipe.
(5) ***** May be five feet when Schedule 40 PVC/DWV pipe is used.
(6) ******Or applicable plumbing code.
C. Multiple liquid waste systems, each with an actual design flow of 5,000 gallons per day (gpd) or less, may be permitted by the department even if they are located on a single lot provided that the disposal systems are set back from each other by a distance equal to the sum of two radii of adjacent circular areas, each circular area representing certain boundaries of a disposal system. The center of each circle is located at a point nearest to the outer boundary of each adjacent liquid waste disposal system. The radius for each circle may be calculated utilizing Table 302.2 below based on the number of bedrooms, or by using the following formula: r = √(A/π) or r2 = A/π, where:
(1) “r” means radius of the circular area measured in feet;
(2) “√” means square root;
(3) “A” means the area of a circle in square feet, calculated as follows:
(a) A = (design flow, gpd) x (1 acre/500 gpd) x (43,560 square feet/acre); or
(b) A = (design flow, gpd) x 87.12; and
(4) π (pi) = 3.1416.
D. Table 302.2 below provides examples of radii for design flows based on number of bedrooms only. Radii for other design flows shall be calculated with the formula above. Separation distances to facilities permitted by other entities, such as the ground water quality bureau, may be considered on a case by case basis.
Table 302.2: Radii for calculating minimum distance between systems on a large parcel
No. of bedrooms Actual flow, gpd Minimum acreage Radius of A, feet 1 150 0.75 102.0 2 300 0.75 102.0 3 375 0.75 102.0 4 440 0.88 110.5 5 500 1.0 117.8 6 550 1.1 123.5
No. of bedrooms
Actual flow, gpd
Minimum acreage
Radius of A, feet
1
150
0.75
102.0
2
300
0.75
102.0
3
375
0.75
102.0
4
440
0.88
110.5
5
500
1.0
117.8
6
550
1.1
123.5
G. If the department discovers that a private drinking water well has been drilled at a location that is not set back from an existing liquid waste system by the distance required in Table 302.1, the department shall:
(1) send a certified letter to the owners of the water well and liquid waste system that identifies the subject water well and liquid waste system, and describes the potential hazards created by insufficient setback;
(2) provide the office of the state engineer with a copy of the letter; and
(3) not administer the water well setback requirements in Table 302.1 pertaining to the subject well provided that the liquid waste system remains in compliance with 20.7.3 NMAC, and is not modified.
[20.7.3.302 NMAC - Rp, 20.7.3.302 NMAC, 9/1/13; A, 9/1/13; A, 9/15/14]