Drainage_and_Flooding_Report-dated_03-10-08

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Mr. Ron Bottoms March 10, 2008 Page 8 of 15 k I o t z associates 5. Do you need to replace the concrete roadway with concrete? This will be a low traffic area. Would asphalt pavement be more economical at this location and if so will asphalt be acceptable to the residents? Recommend that the City consider an option of evaluating utilities to determine if construction of a short section of storm sewer on the north side of the road. The new storm sewer would need a new or upsized outfall. The new storm sewer would be placed outside of the pavement but within the street ROW plus additional inlets would be added to utilize the new capacity of the storm sewer. This option could be constructed without removing the concrete street and could provide much more storm sewer capacity to the area at a reduced cost. A driveway to the back yard of one house would probably need to be removed and replaced. Coordination with HCFCD will be required if a new outfall pipe is constructed. Short Term Drainage Project 2.) Creekmont Park Overflow Path The City Park is located at Willow Creek Drive (see Exhibit 7). The park has a parking lot slab which has an elevation higher than the street elevation leading into the parking area. As a result, the natural drainage down the street toward the parking lot is impeded and flow backs up in the street and eventually adjacent properties. From examination of the LiDAR contours in Exhibit 7, it appears that the natural flow path is through the City Park and into Big Island Slough but the parking lot is acting like a restriction to the overland flow capacity. Currently the park was planned to drain north then east to a small shallow outfall ditch that meanders behind homes and makes its way to Big Island SIough. The park with the constructed some elevated trails currently drains poorly and has standing water or wet areas in portions of the park. The park area also needs improved drainage. The City informed us that they plan to lower the parking lot elevation and convey the accumulating surface runoff away from Willow Creek Drive and through the park to Big Island Slough. Several options exist to help address the local flooding situation. One solution is to improve the current drainage path by constructing a larger open ditch drainage system to Big Island Slough, by constructing a storm sewer system along the path of the current open ditch or by constructing a storm sewer from the Park directly north to H Street. Each of the options listed above the merit and different costs. There exists benefits to all the property owners along the outfall path by the improved drainage system provide for better drainage all the way to Big Island Slough. The requirements of each solution would be enough depth and capacity to drain the Willow Creek Drive area. An open ditch relief path along the current drainage path could work but additional ROW would probably be required to build a larger open ditch. This solution my be economical if additional ROW is available from all the property owners from the Park east to Big Island Slough.