New Mexico Administrative Code › Title 20 - ENVIRONMENTAL PROTECTION › Chapter 6 - WATER QUALITY › Part 7 - GROUND WATER PROTECTION - SUPPLEMENTAL PERMITTING REQUIREMENTS FOR COPPER MINE FACILITIES › Section 20.6.7.22 - REQUIREMENTS FOR COPPER CRUSHING, MILLING, CONCENTRATOR, SMELTING AND TAILINGS IMPOUNDMENT UNITS

Current through Register Vol. 35, No. 13, July 16, 2024
A.
Engineering design requirements.
At a minimum, the following
				requirements shall be met in designing crushing, milling, concentrating,
				smelting and tailings impoundment units at copper mine facilities unless the
				applicant or permittee can demonstrate that an alternate design will provide an
				equal or greater level of containment.
(1)
New crushing and milling units.
New crushing and milling units,
				including associated ore storage, except when located within the open pit
				surface drainage area, shall be designed to contain and manage all materials
				containing water contaminants that have the potential to migrate to ground
				water and cause an exceedance of applicable standards on concrete or low
				permeability surfaces approved by the department.
(2)
New concentrator units.
New
				concentrator units shall be designed to contain and manage in tank and pipeline
				systems designed and operated pursuant to 20.6.7.23 NMAC all materials
				containing water contaminants that have the potential to migrate to ground
				water and cause an exceedance of applicable standards. Tailing and concentrate
				thickener tanks may be constructed with concrete or low permeability bottoms
				consisting of a minimum of 12 inches of soil that has a minimum re-compacted
				in-place coefficient of permeability of 1x10-6
				cm/sec. The tank designs shall be based on plans and specifications signed and
				sealed by a licensed New Mexico professional engineer. For low permeability
				bottoms, such plans and specifications shall describe how process rates,
				material density and settling rates were considered in the design to minimize
				infiltration such that water contaminants in the tank will not migrate to
				ground water and cause an exceedance of applicable standards.
(3)
New smelting units.
New
				smelting units shall be designed to contain and manage on impermeable surfaces
				all materials, including associated slag and flue dust, containing water
				contaminants that have the potential to migrate to ground water and cause an
				exceedance of applicable standards.
(4)
New tailings impoundments.
Tailings impoundments shall be designed according to the following
				requirements.
(a) Stormwater run-on shall be
				diverted and/or contained to minimize contact between stormwater run-on and the
				tailing material.
(b) Seepage from
				the sides of a tailing impoundment shall be captured and contained through the
				construction of headwalls, impoundments and diversion structures as
				applicable.
(c) Ground water
				impacted by the tailing impoundment in excess of applicable standards shall be
				captured and contained through the construction of interceptor systems designed
				in accordance with Subparagraph (d) of Paragraph (4) of Subsection A of
				20.6.7.22 NMAC.
(d) The applicant
				shall submit design plans signed and sealed by a licensed New Mexico
				professional engineer along with a design report that includes the following.
(i) The annual volumes and daily maximum
				design rates of tailings or other discharge approved by the department to be
				deposited in the impoundment.
(ii)
				The topography of the site where the impoundment will be located.
(iii) The geology of the site.
(iv) The design footprint of the tailing
				impoundment.
(v) The design of
				tailing seepage collection systems, to be proposed based on consideration of
				site-specific conditions.
(vi) The
				design of stormwater diversion structures to minimize contact between
				stormwater run-on and the tailing material. The design shall consider the
				amount, intensity, duration and frequency of precipitation; watershed
				characteristics including the area, topography, geomorphology, soils and
				vegetation of the watershed; and run-off characteristics of the watershed
				including the peak rate, volumes and time distribution of run-off
				events.
(vii) An aquifer evaluation
				to determine the potential nature and extent of impacts on ground water from
				the tailings impoundment based on the proposed tailings impoundment design. The
				aquifer evaluation shall include a complete description of aquifer
				characteristics and hydrogeologic controls on movement of tailing drainage and
				ground water impacted by the tailings impoundment.
(viii) A design report for a proposed
				interceptor system for containment and capture of ground water impacted by the
				tailings impoundment based on the aquifer evaluation required in Subparagraph
				(d) of Paragraph (4) of Subsection A of this section. The design report shall
				include, at a minimum construction drawings and interceptor system performance
				information, recommended equipment including pumps and meters, recommended pump
				settings and pumping rates, methods for data collection, and a demonstration
				that the permittee has adequate water rights to operate the system as designed.
				The design report shall include a demonstration that interceptor system design
				will capture ground water impacted by the tailings impoundment such that
				applicable standards will not be exceeded at monitoring well locations
				specified by 20.6.7.28 NMAC. The interceptor system shall be designed to
				maximize capture of impacted ground water and minimize the extent of ground
				water impacted by the tailings impoundment.
(ix) Within 120 days of seepage collection
				and interceptor well system construction, or liner system installation a final
				report shall be submitted to the department that includes complete as-built
				drawings and a summary of how the items in Subparagraph (a) thru Subparagraph
				(d) of Paragraph (4) of Subsection A of 20.6.7.22 NMAC were incorporated into
				the design.
(e) If the
				department determines that the proposed tailings impoundment, seepage
				collection and interceptor systems when constructed and operated in accordance
				with the design plan specified in this paragraph would cause ground water to
				exceed applicable standards at monitoring well locations specified by 20.6.7.28
				NMAC, the department shall require additional controls, which may include but
				are not limited to, a liner system as additional conditions in accordance with
				Subsection I of 20.6.7.10 NMAC.
(5)
New dry stack tailing piles.
New dry stack tailings piles shall comply with the material characterization,
				engineering design, construction, and operational requirements of 20.6.7.21
				NMAC, as applicable.