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Well House No. 7 Feasibility Study City of Lino Lakes, MN WSB Project No. 013434-000 Page 4 The test well was constructed using a 10-inch outer casing and a 6-inch inner casing. The 10- inch casing was extended to 225-feet to temporarily seal off the glacial drift, uncemented Prairie du Chien, and top uncemented portion of the Jordan formation. A 10-inch nominal open hole was drilled to a depth of 287-feet to the bottom of the Jordan formation. The 6-inch casing was set to 230-feet to penetrate approximately 20-feet into the Jordan formation to ensure a stable borehole, without compromising yield. The 6-inch casing was grouted while pulling back the 10-inch outer casing. The 10-inch outer casing was entirely removed to allow the formation to better absorb the grout and provide an improved sanitary seal between the inner well casing and uncemented formations. 3.1.3 WELL CAPACITY Test pumping of the Jordan formation at 280 gallons per minute (gpm) resulted in a drawdown of 11 feet for a specific capacity of approximately 25 gpm per foot of drawdown. This specific capacity is very high for a test well. Assuming a conservative estimate for specific capacity of 20 gpm per foot of drawdown, pumping a municipal well at 1,000 gpm would result in a drawdown of approximately 50 feet which is not excessive for a municipal well. Currently, the City’s average well capacity is approximately 950 gpm. 3.1.4 WATER QUALITY Water quality from the test well indicated iron and manganese concentrations above the recommended Secondary Maximum Contaminant Levels (SMCL). Treatment for SMCL contaminants is optional; however, these contaminants can cause undesired discoloration and unpleasant taste in drinking water. In addition to aesthetics, elevated levels of manganese (100 ppb for infants and 300 ppb for adults) in drinking water can have negative health effects in in young children or adults who consume too much water with elevated levels of manganese. Iron bacteria was also present in this well, which may combine with iron, manganese, and oxygen to form deposits of bacterial cells and a slimy material that may allow for the bacteria to attach itself to well column pipe and pump. Iron bacteria is not known to cause disease but may require additional maintenance throughout the life of the well. It should be noted that the water quality observed in Test Well No. 7 is similar to that in the other municipal wells (see table below). Lino Lakes Municipal Well Water Quality Comparison: Well No. Calcium (μg) Iron (μg) Manganese (μg) Well No. 1 75600 839 134 Well No. 3 79600 ND 339 Well No. 4 63900 147 61.7 Well No. 5 78400 356 170 Well No. 6 84000 93.2 390 Test Well No. 7 58600 638 65.2 Average 73350 415 193 *1μg = 1ppb