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Well House No. 7 Feasibility Study City of Lino Lakes, MN WSB Project No. 013434-000 Page 3 3. TEST WELL BACKGROUND During the 2008 Water Supply Plan review, the City was pre-approved for two additional production wells, Well No. 7 and 8. In 2017 the DNR was ordered to take measures to immediately amend all appropriations permits within a 5-mile radius of White Bear Lake, which resulted in the suspension of the original approval. As of 2019, DNR approval is still suspended pending additional information from test wells, which are recommended to examine a site for geologic conditions, potential well interference, water quality, and aquifer capacity. In the Spring of 2019, Anoka County provided the City of Lino Lakes access to the site for the construction of Test Well No. 7. The southwestern corner of the property was chosen for a future production well based on future site layouts provided by Anoka County, local geology, topography, and proximity to existing utilities. Two test wells were constructed on the southwest corner of the 509 Birch Street property. Both test wells were termed Test Well No. 7, however the first attempt was sealed after it failed during drilling. Minnesota Department of Health (MDH) assigned the failed Test Well No. 7 the Well and Boring Sealing Unique Number 841553. The second Test Well No. 7 was successful and was assigned Well and Boring Unique Number 843388. Well and boring reports for both wells are included in Appendix B. 3.1 TEST WELL RESULTS Test Well No. 7 was completed as an open hole well (no screen installed) in the Jordan Sandstone (Jordan) formation in the southwest corner of the site (see Figure 1). This location on the property was determined acceptable for production Well No. 7 based on the observed geology, potential well capacity, water quality, and absence of adjacent well interference. 3.1.1 GEOLOGY The geology in this area typically consists of sand and gravel overlying glacial deposits. Glacial drift and the St. Peter, Prairie du Chien, Jordan, St. Lawrence, Tunnel City, Wonewoc, Eau Claire, and Mt. Simon formations are all present around the Lino Lakes area. The City’s existing wells currently utilize the Prairie du Chien, Jordan, and St. Lawrence formations. The glacial drift at the test well location is unconsolidated Quaternary deposits consisting of layers of fine to pebbly sand, gravel, silt and clay that are approximately 127-feet thick. The glacial drift can be vulnerable to pollution and is not generally used for high capacity production wells due to the high likelihood of domestic well interference. The Prairie du Chien formation in this area is approximately 50-feet thick and is sometimes used for high capacity production wells. At this location, a zone of uncemented limestone, mixed with glacial sands was encountered 10-feet into the Prairie du Chien. The uncemented formation was deemed unstable. The Jordan formation in this area is approximately 105-feet thick and is most frequently used for high capacity production wells within the City. The top part of the formation at the test well location consisted of 10-feet of unconsolidated sandstone and 95-feet of mostly consolidated sandstone immediately below. 3.1.2 TEST WELL CONSTRUCTION During the construction of the failed bedrock test well, the well contractor (contractor) drilled approximately 142-feet into the Prairie du Chien formation. The Prairie du Chien formation at this site was uncemented, not stable, and continually collapsed as the contractor attempted to reach the Jordan formation below. The contractor decided to change drilling methods and was able to reach a depth of approximately 187-feet, almost the depth of Jordan formation. During this construction, the well continued to collapse within the uncemented zone and produced sediment filled water. In working with the contractor and another local well drilling contractor, it was concluded that a bedrock test well would not be feasible in this unique formation using cable tool drilling methods. It was recommended that the failed test well be sealed and a screened or bedrock test well be constructed using a rotary drill rig.