SITE INFORMATION AND CORRESPONDENCE

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Mr. Kevin Graves April 28, 2006 Page 5 Paragraph five, the second paragraph of page 2, of "The Work Plan is not approved" letter states: The reason or justification for measuring the water levels in monitoring well MW1, MW2, and MW4 every 20 minutes for a five day period was not clear. Provide a justification for this work and explain how it will be used as a preliminary evaluation for performing groundwater extraction from MW3 and MW4. The EHD already had a copy of the December 30, 2005 report on this assessment, the one with the lengthy title: Static Water Level Monitoring of Wells MW-1, MW-2, and MW-4 November 30 to December 05, 2005 — Assessment of Hydraulic Continuity/Sanitary Seal Hydraulic Integrity of Thornton Municipal Supply Well No. 2 With Respect to the Aquifer Shallower Than 30 Feet, that was submitted December 30, 2005 (Attachment E), when the January 13, 2006 "The Work Plan is not approved" letter was issued. The work plan clearly stated: As a preliminary step for an evaluation for performing groundwater extraction from monitoring wells MW-3 and MW-4 the potentiometric surface response to the pumping regime of Thornton Municipal Supply Well No. 2 will be assessed through measuring the water levels in monitoring wells MW-1, MW-2, and MW-4 every 20 minutes for a five day period. The potentiometric surface response monitoring will be conducted prior to the installation of the proposed deeper monitoring wells. These data will be presented as hydrographs and as a graph depicting variations in gradient direction. As to the first sentence of the fifth paragraph of "The Work Plan is not approved" letter - this is embodied in determining "the potentiometric surface response to the pumping regime of Thornton Municipal Supply Well No. 2. The proposed/implemented method is how one determines the water level affect of the pump going on and off. As shown in the report on the activity, there is no discernable response to the water supply well going on and off indicating that there is no hydraulic connection. The 70 foot well seal that extends ten feet into materials that are "blue clay & shale" has created a hydraulically effective barrier between the shallow groundwater in the upper 60 feet, as measured in the partially penetrating 30 foot deep monitoring wells. As to the second sentence of the fifth paragraph of "The Work Plan is not approved" letter - any first year geohydrology student would understand that performing single well pump tests (this is after all what a step drawdown test is) or constant rate tests within the drawdown cone of another well coming on and off is likely to be uninterpretable, and therefore must be carefully planned to avoid the water level response interference. As shown in the report on the activity, this will be less of a concern. A GROUND WATER CONSULTANCY H2OGEOL