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Feasibility Report TKDA Project No. 18196.000 City of Arden Hills Page 8 Drainage and Detention Ponds: Two stormwater detention ponds have been identified in the project area. The first is located northeast of 1399 Arden Oaks Drive, and the second is located west of 1469 Arden Oaks Drive. These two ponds have collected some sediment and have partially lost their full ability to treat storm water before discharging to natural bodies of water. At this time, it does not appear that a full cleanout would be necessary, but the ponds may benefit from cleanup around the inlets and outlets. Further investigation and survey may be required to investigate and evaluate the benefits and cost of the maintenance; these costs were not factored into the cost estimates in this report. The cul-de-sac east of Snelling Avenue appears to have consistent ground water along the south curb line. Upon the field inspection, several drain tile and sump pump discharges were noted in the cul-de-sac area extending down the street towards Snelling Avenue. Several residents explained the drainage issues they had in this area as well. It was noted that water comes from the back yards in between the houses to the street on the south side of Arden Oaks Drive. Arden Oaks Neighborhood Proposed Improvements: Streets: Considering the existing condition, deterioration factors, and geotechnical investigation, a full depth pavement reclamation is proposed for the streets within the project area. With pavement ratings below 45 out of 100, mill and overlay provides only limited benefit as the underlying base pavement materials have deteriorated to a point that cracking would reflect to the new bituminous overlay almost immediately. If mill and overlay is selected, a portion of the project may still need full depth reclamation according to the forensic report and the geotechnical report including Arden Oaks drive from Snelling Ave North 400 feet east to the cul-de-sac. For the rest of the area, a mill and overlay can be shorter- term street improvement (10-year improvement). However, reclamation of the street section can provide more structural aggregate base and disrupt the existing frost heaving that has breached the existing aggregate base and bituminous surface (15-year improvement plus future mill and overlay opportunity). Reclamation is traditionally considered a longer-term maintenance task in which future mill and overlays can be done to extend underlying pavement and base longevity. A mill and overlay will likely begin to show cracking within one to two years following the conclusion of the project. Table 1 presents the coring information gathered from the geotechnical report coring log (Exhibit 7) and forensic pavement report (Exhibit 1). Table 1: Coring Logs Core Bituminous (in) Aggregate Base (in) Total (in) Subgrade Soil Type Mill & Overlay Depth (in) Reclaim Depth (in) A 5 12 17 Sandy lean clay *NR 12 B 5.5 8 13.5 Sandy lean clay *NR 12 C 6 6 12 Sandy lean clay 2 12 D 5 8 13 Fill: Sandy lean clay 2** 12 E 6 5 11 Sandy lean clay 2 12 F 6.5 7 13.5 Sandy lean clay 2 12 G 5.5 5 10.5 Fill: Sandy lean clay 2 12 H 6 13 19 Fill: Sandy lean clay 2 12 *NR – Not recommended by report ** Potential area subject to raveling after milling Figure 5. Ground Water Emerging from May 2019 Arden Oaks Drive DRAFT REPORT 7-8-2021