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Res. 8180, Considering Stormwater Infiltration Program Appeals in Area G <br />Page 2 <br />The property owners are appealing for the following reasons: <br />A2. High Groundwater Elevation <br />Property owners allege that a high <br />groundwater table exists on their property. <br />However, a 16 -foot deep geotechnical soil <br />boring was performed near the proposed <br />basin location that encountered <br />groundwater at approximately 6.5 feet <br />below the surface, whereby providing the <br />necessary vertical separation of three feet <br />required by the watershed district. <br />A3. Impermeable Soils <br />Property owners allege medium <br />permeability "as noted in city report'. <br />However, n is unknown what report the <br />property owners are referencing. In addition, the upper layers of the ground (topsoil) are <br />commonly less permeably than those underlying (sand) which is a reason that the basins are <br />over -excavated to approximately three feet and backfilled with select granular material to <br />promote good infiltration into the ground. The nearby soil boring indicates underlying soils as <br />"poorly graded sand with silt" which is well suited for infiltration. <br />P. <br />A11. Other Physical Parameters <br />In the appeal, the property owners describe various scenarios of drainage patterns in their <br />back yard, side yard, and front yard/street. The back and side yard issues are related to <br />drainage from adjacent private properties and are unrelated to runoff from the city street. The <br />narrative provided by the property owners regarding front yard/street runoff alleges homes <br />across the street that are higher in elevation contributing additional runoff to the proposed <br />basin. Runoff from properties across the street will not cross the street due to the cross -slope <br />crown in the middle of the new street. Runoff will drain down gradient in the gutter on the <br />respective sides of the street. <br />Throughout the appeal narrative, property owners also describe infiltrated water moving "in <br />the horizontal direction toward our house" from the back, side, and front yards. This claim is <br />illogical since water will be drawn downward due to gravity forces, not sideways from all <br />directions toward the basement. In addition, this appeal parameter is related to <br />constructability and function of the proposed basin, which is not addressed by the property <br />owners. <br />- Engineering staff and Streets & Utilities Committee both recommend den in this appeal. <br />