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XII. Seneca II Technical Revision 45 (2007) Monitoring Program Changes
<br />Due to the closing of the Seneca II Mine, SCC has requested a reduction in monitoring frequencies of streams,
<br />springs and wells. These reduced monitoring frequencies will be continued until a year or two before final bond
<br />release, at which time monitoring frequencies will be increased. The details of the changes are provided
<br />below.
<br />For ground water monitoring wells, the frequency of water level measurements has been changed from tri-
<br />annual to semi-annual (May/June and September/October). Water quality sampling of alluvial and spoil wells
<br />will remain semi-annual. Water quality sampling of bedrock wells will change from semi-annual to annual
<br />(May/June), since the bedrock wells are subject to less change in water quality than the alluvium or spoils.
<br />Water quality sampling will be discontinued at wells GW-S6-A, GW-S31-A2, GW-S32-A, GW-S33-A, and GW-
<br />S46-A. In the case of the first three wells, they all exist in the Little Grassy Creek Alluvium and are all
<br />downstream of mining areas. However, there is no use of the alluvial water in this area, and a further
<br />downstream well, GW-S70-A, exists in the Grassy Creek alluvium. Well GW-S33-A exists in the Grassy Creek
<br />alluvium downstream of some of the mining area, but GW-S70-A is downstream of the entire mining area and
<br />will continued to be sampled. Well GW-S46-A is in the Cow Camp Creek alluvium, but GW-S69-A is further
<br />downstream and will continued to be sampled. Table 7-99, Ground Water Monitoring Frequencies, has been
<br />revised to reflect these changes. These wells will remain open for sampling, if necessary, prior to bond
<br />release.
<br />For stream sites, monitoring at SW-S2-2, lower Grassy Creek, has been changed from monthly to tri-annual
<br />(spring runoff, post-runoff and baseflow). Monitoring at all other streams in the Grassy Creek basin will remain
<br />tri-annual. Monitoring at stream sites in the Fish Creek basin will remain monthly, May thru July. For spoil
<br />springs, monitoring has been changed from semi-annual to annual (May to July). Table 7-103, Surface Water
<br />Monitoring Frequencies, has been revised to reflect these changes.
<br />XIII. Seneca II Technical Revision 47 (2007) Monitoring Program Changes
<br />• This technical revision assigned ground water points of compliance for the Seneca II Mine. Details for
<br />this revision are found in Attachment 7-3.
<br />References
<br />Colorado Water Quality Control Commission, undated. Notice of Public Rulemaking Hearing Before the
<br />Colorado Water Quality Control Commission, Hearing Date of June 13, 2005.
<br />www.edphe.state.co.us/optwqcc/wqcchom.asp
<br />Cooper, H.H., J.D. Bredehoeft, and I.S. Papdopulos, 1967. Response to a finite diameter well to an
<br />instantaneous charge of water. Water Resources Research, V.3. No. 1, pp. 263-269.
<br />Hem, J.D., 1989. Study and Interpretation of the Chemical Characteristics of Natural Water. U.S.
<br />Geological Survey Water-Supply Paper 2254. 263p.
<br />Office of Surface Mining Reclamation and Enforcement, 1989. "Draft Environmental Impact Statement",
<br />OSMRE-EIS-25.
<br />Skibitzke, H.E., 1963. Determination of the coefficient of transmissibility from measurements of residual
<br />drawdown in a bailed well: In Methods of determining permeability, transmissibility and drawdown, R.
<br />• Bentall, complier, U.S. Geological Survey Water-Supply Paper 1536-I, pp. 293-298.
<br />TR-47 7-388 Revised 1/09
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