Item A: Public Hearing onMetro Plan Amendment (Delta Sand and Gravel)

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Oregon Department of Geology and Mineral Industries - Mine Dewatering and Ground W... Page 1 of 4 ~LAW ... .' EnviIollmental ;"UlYl' Al1ian~ Worldy.~de ej. . ..... .:........................................ . . " :t T_.8..QQ.~l I;.~.LA.VY T...N.~.w.$.. pg.Gne.f$ :~l, Be..$..Q.Y.f.G.e..$.. 'Y...G~lJny.Q.I.Y.~.Q. Choose a language: [.Eng.H$.h I .l;.$.p~.o.Q.I.] Search: . ~"'i"; , '.; . ! .' I , :;, ~ : I .. Adobe Acrobat version I Microsoft Word Version I .P.ri.nt.e.LEr.i.e'O.Q.ly...V.e..r~J.Qn Oregon Department of Geology and Mineral Industries - Mine Dewatering and Gro Water Protection Author: Oregon DOGAMI, 04/18/2005 Mine Dewatering and Ground Water Protection Mine or pit dewatering is an essential part of resource extraction at many of the aggregate operations throughout Oregon. DOGAMI classifies dewatering to be the withdrawal of ground water with a result, decline in the water table or hydraulic head within an aquifer. As the number of ground water users increases and aquifers are designated as limited or critical, mine operators need to be informed about th potential for off-site impacts from dewatering. To ensure the protection of ground water it is necessary : permittees to consider certain issues prior to conducting this activity. These issues are both regulatory a technical in nature and include permitting, collection of baseline data, monitoring and/or modeling. Thi paper is a discussion of these issues and provides operators with an insight to the best management practices for conducting mine dewatering. REGULATORY ISSUES DOGAMI has a statutory directive to prevent or mitigate off-site impacts to natural resources from mining operations. Ground water is a natural resource that can be affected by mining and as a result dewatering is regulated by this department. Permittees should be aware that dewatering is generally allowed only if it is specified in their permit. Filing an amendment application and mine dewatering pIa is required if dewatering is not authorized in the original permit. Consultation with DOGAMI will assis the permittee in identifying those concerns that need to be addressed in order for the dewatering plan to be considered complete. The technical aspects of a dewatering plan are to follow. Sites permitted in the 1970's and early 1980's may have approved reclamation plans that may not specifically allow or prohibit dewatering nor was it evaluated. Permittees in this category are advised to contact DOGAMI for an evaluation of the likely impacts from dewatering. Data collection may be need for protection against frivolous claims of well damage by adjacent landowners. Discharging mine water is a component of dewatering that may also require permitting. If water is pumped from a gravel pit or rock quarry and is discharged to a surface water stream or off-site then a National Pollutant Discharge Elimination System (NPDES) I200A permit is required. Operators shoulc be aware that holding a 1200A permit alone does not qualify as an approval by DOGAMI to perfonn dewatering activities. The Oregon Water Resources Department (WRD) is the issuing agency for water rights in the state. Permittees should determine if their dewatering operation constitutes a consumptive use such as gravel washing or dust suppression. If more than 5000 gallons per day of ground water is consumed for these file://X:\0290 Delta Sand & Gravel\04-0020 Pit Expansion\Hydrualic Barrier\OreQon Dena... 11 /1 /?()()(-)