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Home My WebLink AboutNC0090212_Other Agency Documents_20160603Guidance for determination of NPDES regulatory status of various discharges on a mine site (Active and Inactive Mines Jun 3, 2016; NC DEQ Stormwater Program Feature contributing not Rule or permit citations; to a discharge Conditions and comments sw ww regulated other guidance 1 Undeveloped areas at the site, w/o permitted Other areas closed out and fully reclaimed, too. X Excluded from stormwater def. in mining activity 40CFR122.26(b)(14) 2 Overburden stockpile Not mixed with any mined materials or other wastewater X 'overburden' at drainage. Better when fully stabilized. 40CFR122.26(b)(14)(iii) 3 Soil borrow area drainage Like a borrow area at a construction site. X DEQ BPJ interp. of citation above. 4 Vehicle maintenance areas Additional monitoring, if qualified by motor oil usage. If X Consistent w/other regulated activity commingled with WW, discharge instead subject to identified at 40CFR122.26(b)(14)(viii); wastewater sampling; additional 0&G sampling could be DEQ BPJ recommended but not required (per current permit). 5 Equipment boneyards X 'refuse sites' in 122.26(b)(14) 6 AST Secondary containment release If uncontaminated. X 'tank farms' in 122.26(b)(14) 7 Access and haul roads, without dust control Except: roads off -site are not regulated X X, off -site 'access roads' in sw definition in roads 40CFR122.26(b)(14) 8 Access and haul roads, with dust control, when If just stormwater runoff from sprayed roads. OK to spray X Above citation plus DEQ BPJ for spraying it's stormwater with mine pit water as long as no significant or sustained mine dewatering water for dust control. flow, or discharge to surface waters results. Any Inspector BPJ to determine if excessive chemicals used should be approved and used in proper flow or potential WQ problem is basis doses to prevent aquatic toxicity — refer to approved for wastewater determination. PAMS list or consult DWR Aquatic Toxicology Branch. 9 Access and haul roads, with dust control, when If recycled or process wastewater sprayed, or if spraying X NPDES process ww definition at it's wastewater excessive enough to cause sustained flow or discharge to 40CFR122.2 plus DEQ BPJ on prudent surface waters. Also wastewater if any chemicals applied protection for NC surface waters. are not approved by DWR Aquatic Toxicology or are used Inspector BPJ to determine if spray in amounts that may cause aquatic toxicity. excessive. 10 Stormwater-only sediment basins If no wastewater contribution (mine dewatering, process X Stormwater in: stormwater out, DEQ BPJ ww, flow from active mining area.) 11 Stormwater-only sediment basin cleaning spoil Spoil may not impact wetlands. X 15A NCAC 213.0231, NC wetlands drainage standards 12 Wastewater treatment or recycle basin cleaning Includes basins that treat wastewater or mine X Wastewater in: wastewater out, DEQ spoil drainage dewatering water. BPJ 13 Processing plant: recycle water overflow or Even if caused by rainfall or mixed with Stormwater X 40CFR122.2 def. process ww; process wastewater runoff. Except: segregated areas that do not drain plant yards' in stormwater definition at wastewater would be stormwater, but these are rare. X, seg. area 122.26(b)(14) 14 Final product stockpile drainage, when it's For most construction materials including sand, gravel, X final products' in stormwater def. at stormwater and stone; industrial sand. 40CFR122.26(b)(14) 15 Final product stockpile drainage, when it's For some mineral mines where 'final' product is subject X 'comes into direct contact wastewater to further processing; and if final product exposes with... intermediate product final minerals, metals, or chemicals with aquatic toxicity or product...' 40CFR122.2 Def. of process other pollutant risk: DEQ may regulate as WW. wastewater; DEQ BPJ 16 Mine ILR dewatering, pumped or drained by Including contributions from rainfall and groundwater. X 40CFR436.21, .31, and .41; efforts of the operator DEQ BPJ default for all mines 17 Mine pit dewatering, via overflow due only to DEQ considers these types of discharges, including those X 40CFR436.31 Construction sand & gravel rain or groundwater seepage from clay pits (not specified in regs), as regulated have effluent limits and "mine wastewater. Except: such wet pit overflows from 436.21 X, crushed dewatering" includes wet pit overflows; stone wet pit overflow 436.41 Industrial sand, same; Guidance for determination of NPDES regulatory status of various discharges on a mine site (Active and Inactive Mines Jun 3, 2016; NC DEQ Stormwater Program Feature contributing not Rule or permit citations; to a discharge Conditions and comments sw regulated other guidance Crushed Stone treated as stormwater, as Iona as not DEQ BPJ for 436.21 Crushed stone commingled with process generated wastewater. narrower mine dewatering definition; DEQ BPJ for clay. 18 Mine face / Mine excavation area drainage (not a e.g., mining an area on a mountain side or sand mine X DEQ BPJ; Def. of mine dewatering in pit), when it's stormwater excavation area(s). When water from the mine area is 40CFR436.21, .31, and .41. Situations not "pumped, drained, or otherwise removed where stormwater inside a mine is not from the mine through the efforts of the mine intentionally routed out of the mine by operator efforts. operator." But often mine excavation area drainage will be wastewater per 19. 19 Mine face / Mine excavation area drainage (not a e.g., active mining area on a mountain side or sand mine X Consistent with mine dewatering pit), when it's wastewater excavation area(s). Any "water that is impounded definition in citations above and 'direct or that collects in the mine and is pumped, contact with'40CFR122.2 def. of process drained, or otherwise removed from the mine wastewater. Includes grading, channeling, ditching, or outlet through the efforts of the mine operator" is construction intended to remove/drain subject to effluent limitation guidelines. Also, mines water from the active mining area. If where mine face exposure results in significant risk to exposure includes parameters not in water quality standards (note, an individual permit may NCG02 (metals, for example), a general be required to monitor parameters not in NCG02). permit may not be appropriate. 20 Legacy structures at a closed out and reclaimed And for closed out and fully reclaimed portions of an X Excluded from stormwater def. in mine: e.g. stabilized overburden stockpiles, operating site 40CFR122.26(b)(14); not included in stormwater basins, and pit/quarry overflows process wastewater definition at 40CFR122.2 21 Deemed permitted discharges Subject to NC rule, but not this permit. 2T covers 15A NCAC 2H .0106(f) discharges to the land surface. 15A NCAC 2T .0113(a)(15),(16) Notes: • What is covered by NCG02? Stormwater and wastewater discharges from construction materials quarries, mineral mines, and stand-alone processing plants associated with them; and clay mines. What is not covered by NCG02? Discharges from tourist gem mines; brick manufacturing w/o clay pits (NCG07); coal, peat, oil & gas; metal mining; DOT borrow areas (NCS000250); in -stream sand dredging (NCG52); mine operations already covered under an individual discharge permit. • Wastewater commingled with stormwater is regulated as wastewater. Even if the discharge is rainfall driven. • Whether regulated with a permit under the NPDES program or not, mining discharges may not cause or contribute to a violation of an in -stream water quality standard. Bring DWR RO Supervisor into loop if observed site conditions suggest the potential for a WQS violation. • Whether regulated with a permit under the NPDES program or not, mining discharges or operations may not: drain wetlands due to dewatering in the mine; blow out wetlands due to the volume of discharges; or damage wetlands with pollutants from the mine property. Bring DWR RO Supervisor into the loop if observed site conditions suggest the potential for wetlands damage whether intentional or incidental/accidental. • The receiving water classification may determine the numerical value of the stormwater benchmarks or the wastewater limitations. See permit text. • What if continuous flow measurement of wastewater is impractical or overly burdensome, and discharge isn't pumped (no pump curves)? EPA has advised (3/24/2016) that continuous flow meter may not be necessary or practical in all situations, especially where flow discharge is infrequent; DEQ regions can make accommodations to allow permittees to use an alternative method to estimate discharge flows when appropriate. Consider that discharges to HQWs are subject to flow limits in the permit (based on NC WQS). Permit footnote language came from NPDES WW permit standard language and has remained in NCG02 for several permit cycles; DEQ will revisit at renewal. • Limitation of authority: This guidance table is intended as an on -site aid for DEMLR inspectors and for permittees. It does not replace relevant NC law, federal and state rules, NCG02 permit conditions, DEMLR policy, or DEMLR implementation precedent.