Agenda - Public Works Committee - 09/18/2012

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prepared the plans and specifications and their design will be presented tonight. Four areas were identified as need improvement, each will be discussed in detail along with the proposed improvements. Area 1 (Pond adjacent to Hole #1) There is a large pond along the west side of hole # 1. This pond receives runoff from the area west of TH 47 and discharges through a 12" pipe. This pipe was televised in 2011 and has sags and root intrusions. Stormwater modeling indicates this pipe is undersized for the drainage area. The existing pipe runs through an area between fairways then passes under a tee box and adjacent to and traps and a green before discharging to a ditch. The existing pipe is fairly close to the property line and there are several trees that provide screening for the adjacent properties that would need to be removed. Replacement of the pipe on its current alignment would require extensive restoration and temporary relocation of the tee box. An alternative alignment was selected which will cross the fairway instead of the green and avoid the tee box. This relocation will allow for construction of a surge pond at the downstream end of the pipe which will minimize erosion. This pond will be incorporated as a water feature on the course. The main pond serves as an extended supply for the course irrigation system. An outlet control structure with a removable weir will be installed to allow regulation of the water level in the pond. The realignment will require removal of several large trees. The existing drainage and utility easement will need to be revised to cover the new pipe. The new outlet pipe will be increased to 18" from the current 12" size. Modeling of the existing system indicates the pond would be above normal water level for almost 4 days for the 100 year event, after installation of the new pipe the pond will be above normal water level for just over 2 days. Area 2 (Ponds North and West of the Club House) There are ponds northwest and north of the clubhouse. The northwest pond is connected to the north pond by a culvert under the cart path. The cart path is subject to flooding after a 2 inch rain event. The pipe will be replaced with 3 parallel pipes. The cart path will still be subject to flooding after a 4 inch rain event The design process evaluated raising the elevation of the path; however, this could cause water to overflow the pond bank towards the clubhouse. The 2 inch rain event has a probability of once every 5 years, the 4 inch rain has a 10 year probability. Golf course representatives were contacted during the design process and they felt over topping the path during an event larger than the 10 year event would be acceptable. The culvert under the path at the east end of the north pond will be replaced with twin pipes to provide better capacity and reduce the chance of over topping the path. Area 3 (Area around Holes #15 and #16) There is an existing metal weir across the ditch which provides drainage for the course. The ditch upstream of the weir has silted in and in some places is overgrown with vegetation. The plans propose lowering the weir by 6 inches, removing the decorative rock lining the ditch, lowering the grade of the ditch and replacing the rock. The golf course will performing work work in area 3 to install draintile to address the the saturated soils on the fairway. They will also be stabilizing the pond dug during the summer of 2011. This pond was excavated to provide a drainage way for the saturated soils adjacent to the fairway. Area 4 (Area around Holes #3 and #17) This area receives drainage from an area north of the golf course. There are a series ponds connected by culverts that are in poor condition that will be replaced. Several of the culverts have shifted to the point where the downstream end is higher than the upstream end, which restricts flow. The connecting ditches will be cleaned and regraded as part of the project.