Laserfiche WebLink
Northfield Mine Permit Review <br />June 15, 2007 <br />Page 3 <br />for the design and installation of two additional groundwater monitoring wells in the <br />Chandler Creek alluvium. These should be located near the permit boundary in close <br />proximity to Chandler Creek at an upgradient and downgradient location. <br />3. The construction and integrity of two of the three existing monitoring wells used to <br />monitor the coal seam is a concern. NFO1-A and NF-03A are open-hole construction <br />with no filter pack, well screen, and no bentonite transition seal before placement of the <br />sanitary grout seal. Open hole construction is only advisable in crystalline rock. The <br />water level measurements as shown in Appendix L appear to be inconsistent in these <br />wells as opposed to NF-02 which was constructed with a well screen, filter pack, and <br />bentonite seal. If future monitoring wells are proposed please submit the design plans to <br />the Division for review and approval prior to installation. Guidance for the design and <br />installation of monitoring and observation holes can be found at the Office of the State <br />Engineer (Water Well Construction Rules) 2 CCR 402-2. <br />4. In the Hydrologic Monitoring Plan Item VI. Well Monitoring Plan it is unclear which <br />well permit holders have granted the right to enter their property to perform monitoring. <br />This should be provided and the list of wells should be included here for ease of <br />reference. <br />5. In the BBA Water Consultants report referenced above, one well is identified as having a <br />projected water level change from 0 to 15 fifteen but this well is not included in the well <br />monitoring plan. Please clarify why this well is not included in the monitoring plan to <br />verify the conclusions presented in the report. <br />6. Based on my review of Appendices 1, 2 and 5 presented in the BBA report it appears that <br />two additional wells should be added to the monitoring plan including Well 79354 and <br />Well 3759 due to their completion zone in close proximity to the underlying Ocean Wave <br />Coal (see Appendix 1 -Cross-Section A-A'). There is also a house located in T19 S, <br />R70W, Section 11 located south of Brookside very close to the angle of draw and <br />subsidence monitoring zone. There is no registered well listed for this location, but it <br />should be verified if a domestic or livestock well exists at this location. <br />7. The hydraulic conductivity information derived from pump test data as indicated on page <br />2 of the BBA report should be provided to the Division and incorporated into the permit <br />application package as an exhibit. <br />8. Please incorporate the Mitigation Plan described on page 7 of the April 25, 2007 BBA <br />report into the permit application. <br />9. Since the wells included in the Well Monitoring Plan of the application aze domestic or <br />livestock wells, I recommend that the sampling parameters be changed from iron and <br />manganese only to the parameters listed in Tables 1 through 4 of the Basic Standrards for <br />