Handouts from the January 11, 2006 Council Meeting

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Mr. Ron Wickham Page 2 January 11, 2006 Anderson Brothers Construction Atlas HA-380 depicts the watershed to be made of Quaternary glacial drift overlying Precambrian bedrock. The glacial drift deposits can consist of mixtures of clay, silt, sand, and gravel. The USGS identifies the Property as sand and gravel surficial outwash, with a saturated thickness between 100 and 200 feet. It states that the water table is shallow and unconfined, and that the aquifer's high porosity and permeability often permit yields of several hundred gallons per minute (gpm) to large diameter wells. The USGS estimates the transmissivity j (i.e., the saturated thickness multiplied by the hydraulic conductivity) of the area to be between 10,000 and 100,000 gallons per day per foot of aquifer. Atlas HA-380 shows shallow groundwater between 1200 and 1250 feet National Geodetic Vertical Datum (NGVD) for the Property. it also shows groundwater flow to be from the northwest to the southeast from Mayo Lake toward East and West Twin Lakes; this estimate of flow corresponds with the direction implied by the normal water levels for these lakes given on the Nisswa, Minnesota USGS topographic map. We have reviewed some of the logs for wells shown on the attached Nearby Water Wells Mapped by the MN Geological Survey diagram. The geologic descriptions on these logs generally agree with those in Atlas HA-380. However, the wells shown on the attached diagram are only subset of the wells listed in CWI for the six Public Land Survey sections nearest to the site; we have attached the full CWI list for these sections. We also reviewed the gradation results of eight soil samples that you supplied to us that were collected from exploratory borings on the Property. Conclusions The possibility of a petroleum release does exist in any construction or mining operation that involves machinery. However, if an appropriate Spill Prevention, Control, and Countermeasure (SPCC) plan is followed, the risk to the environment can be greatly reduced, possibly to the point of being eliminated. Common SPCC elements include secondary containment for storage of hazardous materials or petroleum (e.g., double-walled aboveground storage tanks [ASTs] or secondary containment structures for ASTs and fuel transfer areas) and response plans for immediate recovery of releases. Minnesota Pollution Control Agency (MPCA) protocols and guidance for reporting and responding to any spill must be followed at a minimum. Based on the above information, it appears that groundwater is flowing away from Mayo Lake toward East and West Twin Lakes. If a petroleum release is not contained or recovered and is large enough to leach to the groundwater table, its plume will likely flow in the same direction as the groundwater, away from Mayo Lake. Based on the geologic descriptions and soil gradation results, we estimate that the hydraulic conductivity of the underlying aquifer is about 10-2 centimeters per second or 28 feet per day, with a porosity of about 25 percent. If governed by the surface water elevation differences between Mayo Lake and East and West Twin Lakes, the groundwater flow velocity would range between 0.1 and GNIE CONSULTANTS,INC.