N.M. Admin. Code § 20.7.3.501

Current through Register Vol. 35, No. 23, December 10, 2024

Section 20.7.3.501 - DESIGN; LIQUID WASTE TREATMENT UNITS; GENERAL

A. Plans for treatment units that have not been previously approved by the department, including septic tanks, shall be submitted to the department for approval and certification. Such plans shall show all dimensions, reinforcement, structural calculations and such other pertinent data as may be required by the department. Plans for advanced treatment units shall be submitted to the department for review by the wastewater technical advisory committee pursuant to 20.7.3.905 NMAC. Plans for advanced treatment units that have not been previously approved by the department shall meet the requirements set forth by the wastewater technical advisory committee. All plans shall be stamped by a professional engineer.

(1) Septic tanks shall be recertified on an annual basis. A recertification fee is required pursuant to 20.7.11.9 NMAC. Failure to recertify shall result in the suspension of department approval.

(2) Failure of the manufacturer of an advanced treatment unit to comply with the conditions of approval by the department shall result in non-approval or suspension of department approval for the advanced treatment unit.

B. All treatment units and tanks, regardless of material or method of construction and unless otherwise specified in 20.7.3 NMAC, shall:

(1) be designed and constructed to withstand all reasonable lateral earth pressures under saturated soil conditions with the tank empty;

(2) support a minimum live load at the surface of 300 pounds per square foot with three feet of cover unless heavier loads are expected;

(3) not be subject to excessive corrosion or decay;

(4) have the manufacturer's name, New Mexico registration number, year of construction and tank capacity in gallons permanently displayed on the tank above the outlet pipe;

(5) be watertight;

(6) not be constructed or manufactured on site, in the ground, when saturated soil conditions during construction are closer than three inches to the bottom of the excavation;

(7) be protected against flotation under high groundwater conditions and for units installed in floodplains;

(8) be installed so that they are easily locatable and accessible;

(9) be approved by the international association of plumbing and mechanical officials (IAPMO); or meet IAPMO minimum standards as demonstrated to the department by approved laboratory testing; or meet all requirements of 20.7.3.501 and 502 NMAC as certified by a professional engineer; or be recommended by the wastewater technical advisory committee and approved by the department; and

(10) all access risers shall be attached to the treatment unit with a watertight or water resistant seal.

C. Treatment units may be constructed of the following materials:

(1) precast reinforced concrete;

(2) poured-in-place concrete;

(3) fiberglass;

(4) polyethylene; or

(5) other materials as approved in writing by the department.

D. Metal, wooden, concrete block and homeowner built tanks are prohibited.

E. A secure lid shall consist of one or more of the following:

(1) a padlock;

(2) a twist lock cover requiring special tools for removal;

(3) covers weighing 58 pounds or more, net weight;

(4) a hinge and hasp mechanism that uses stainless steel or other corrosion resistant fasteners to fasten the hinge and hasp to the lid and tank for fiberglass, metal or plastic lids; or

(5) other mechanisms approved by the department.

F. Wherever vehicular traffic is anticipated to cross over the liquid waste treatment unit, pump station or pump chamber, the unit shall be designed by a professional engineer to withstand the anticipated traffic loading.

G. All solid wall pipe connections, fittings and penetrations shall be watertight.

H. Each tank shall be structurally designed to withstand all anticipated earth or other loads. All septic tank covers shall be capable of supporting an earth load of not less than 300 pounds per square foot when the maximum fill coverage does not exceed three feet. All access risers covers shall be capable of supporting a live load of not less than 300 pounds per square foot.

I. Fiberglass or reinforced plastic septic tanks shall be certified to IAPMO standards. Fiberglass or plastic septic tanks shall be installed according to the manufacturer's instructions. A copy of the manufacturer's installation instructions shall be available for inspection by the department at the installation site.

J. Concrete liquid waste treatment units.

(1) Minimum concrete thickness.

(a) walls: two and one-half inches in thickness.

(b) floors: three inches in thickness.

(c) covers: three inches in thickness.

(2) Floors shall be an integral part of the tank.

(3) Where sections are used, tongue and groove joints or keyways shall be used and shall be sealed with an approved sealer and shall be watertight.

(4) Poured-in-place tanks shall be designed and certified by a professional engineer.

(5) All concrete liquid waste treatment units, except those approved for use utilizing concrete meeting type V specifications, shall be protected from corrosion by coating internally with an approved bituminous coating or by other acceptable means. The coating shall cover all exposed concrete and shall extend to at least six inches below the waterline.

(6) Treatment unit construction materials shall meet the following minimum specifications:

(a) concrete strength - 3500 psi @ 28 days, density 140 PCF;

(b) cement Portland type II or V per the latest version ASTM specifications;

(c) admixtures per the latest version of ASTM specifications; and

(d) reinforcing per the latest version of ASTM specifications for steel bars, grade 40/60 or equivalent.

(7) Be installed level on undisturbed or compacted soil, 1/4 to 3/4 inch pea gravel or sand.

N.M. Admin. Code § 20.7.3.501

20.7.3.501 NMAC - Rp, 20.7.3.501 NMAC, 9/1/13; A, 9/1/13