Otte Enterprises, Cardinal Engineering, and Thelen Associates were contracted by the Sanitation District No. 1 (CIP No. S-578-04) in late 2012 to conduct a Drainage Basin Study for the large lake that serves the Sherwood Condominium complex. Sherwood Lake is a 2.8-acre man-made lake in the Sherwood Lakes condominium community located in Boone County, Kentucky. Sherwood Lake functions as the storm water retention basin for the majority of the Sherwood Lakes community. The watershed draining to Sherwood Lake is approximately 75 acres. This includes several off-site properties as well as the Sherwood Lakes community. The majority of the off-site portion of the Sherwood Lake watershed is now developed mostly as commercial and residential.
The Sherwood Lake shoreline has been experiencing erosion failure, causing the lake to widen and allowing the shoreline to get closer to residential buildings that surround the lake. This has been an issue for at least the past ten years and probably started soon after the time the lake was first set up as a storm water retention basin for the Sherwood Lakes community.
The team’s tasks were to: (1) Evaluate the Sherwood Lake shoreline erosion; (2) Review the original drainage report for the Sherwood Lake’s Development; (3) Develop cost effective alternatives with respect to the site condition to address the shoreline erosion; (4) Evaluate the lake depth and the areas surrounding the lake with consideration of the soil type and its possible contribution to the shoreline erosion; and (5) Obtain and review the engineering design plans for the lake’s outlet structure and the dam that was available at the Boone County Planning and Zoning. Cardinal’s tasks were to (1) field survey the lake shoreline and the current lake bottom as well as original lake bottom, (2) prepare a new hydrologic model to evaluate the functionality of the retention basin using the current as-built conditions contained in the 75-acre watershed, and (3) assist with recommendations for shoreline remediation.
The results of our study concluded that: (1) the retention basin was functioning properly and that the basin was actually receiving less volumetric flow for the 2- thru 100-year storm events than the original study anticipated (less overall depth fluctuation), and (3) there was a significant amount of sediment buildup in the lake. Options suggested for shoreline remediation included: (1) do nothing, turn the lake into a dry basin, (3) stabilize the shoreline in place with vegetation, and (4) stabilize the shoreline in place with erosion resistant materials. Cardinal’s fee for the project was $9,350.00. Said project was completed on 1/31/13.