2009-10-22_AgendaPacket - Laserfiche WebLink

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PRE-CONSTRUCTION MONITORING RESULTS WOODBRIDGE NEIGHBORHOOD POROUS PAVEMENT PROJECT, SHOREVIEW GROUNDWATER FLOW DIRECTION Groundwater elevations were measured during each sampling event. Elevations are as follows: Depth to Water (TIC) GW Elevations MW-1 MW-2 MW-3 (Piezometer) MW-4 MW-1 MW-2 MW-3 (Piezometer) MW-4 TIC Elevation, ft. 923.03 923.69 928.77 926.91 Base of Boring, ft. (from TIC) 42 45 50 49 6/9/09 37.00 - - - 886.03 6/10/09 - 38.28 43.63 41.79 885.41 885.14 885.12 6/25/09 37.01 38.35 43.51 41.94 886.02 885.34 885.26 884.97 7/9/09 37.08 38.44 43.56 42.04 885.95 885.25 885.21 884.87 Note: TIC =Top Inner Casing The Ramsey County Geologic Atlas shows the general groundwater flow direction (gradient) to the south- southeast. The site-specific groundwater flow direction measured on June 25 and July 9, 2009 was to the southwest, toward Lake Owasso. Groundwater flow directions in small areas can be different than the general gradient and can also change due to climactic conditions, such as a drought. Due to the low level of Lake Owasso (885.23 feet on 7/25/09), we believe the local groundwater flow direction of the unconfined aquifer near the lake has been temporarily shifted from southeast to southwest, but the regional gradient remains to the southeast. Two groundwater gradient site maps for the dates of the sampling events are attached. SUMMARY Collection of the pre-construction monitoring data was intended to establish groundwater quality and elevation conditions prior to installation of this relatively new stormwater infiltration technology. We will schedule the first post-construction monitoring event for December 2009; six months after the last event. We will be looking for trends in the data as it is collected over the long-term. 4