10Siltation Threats North End Cardinal Newman New Elementary School 2014 – 20153. New Magistrates Courts on Decker 20144. Kahn Pond5. Six Storm water discharge pipesSouth end6. Siltation Mounds from Trenholm7. Potential for development of 12 acres
11Do Private Lakes Provide a Public Benefit ? Capture storm water run-offReservoir for intense rain eventsRepository for silt, trash & pollutionAttract wildlife to urban areasAesthetically pleasing to residentsNo cost to the public purse
12What is the Reservoir Effect? Control lake level to provide reservoir for capture of intense rain events.Mitigates downstream floodingIf the private lakes were not there then Richland County Storm Water Department would need to provide services for capture of storm water, silt & pollution.
13RESERVOIR QUESTIONSCan the level of water in private lakes be managed to provide a “buffer” for intense rain events thereby mitigate downstream flooding?Can individual lake owners coordinate to provide a controlled level throughout the watershedCan this be achieved by suitable automatic equipment?If yes, then does this enable private lakes to apply for public financial support?
26North End After Dredging 2011 Creek flowing past Zorba’s and under Decker Bvd.Kahn PondSiltAfter dredging 2011 Lake down - Full depth 5 – 5 ½ feetAfter dredging 2011 Lake down - Full depth 5 – 5 ½ feet
27North End – Feb 2013 – Lake down Kahn PondDepth 5ftDepth 3ft 6inDepth 4ft 6inAfter dredging 2013 Lake down - Full depth 3 ½ – 4 ½ feet
39Siltation in Lake Catherine Serious silt after construction of I-77Eventually dredged by DoT 1993Completely re-silted by 2010HoA spent $100,000 on consultants, lobbyingCost estimated at $980,000Authorities policy not to dredge private lakesHowever, dredging now under consideration with cost share between County, City & FA
40Lake Issues - Summary Sediment from land disturbances - RSD2 Elementary School Trenholm Extn./O’Neil- County Magistrates Courts on Decker- Commercial developments on Two Notch corridor- Potential for development of 12 acres at S. endTrashPollutionSources- Jackson Creek- Decker & Trenholm- six storm-water pipes- a spillway under Trenholm
41Summary continued Key question If the reservoir model works does it open the door for public funding for siltation control?
42ConclusionCary lake is under threat from sedimentation & pollution from storm water run-offCLHA needs professional adviceCLHA Water Quality Committee has obtained quotes from four consulting organizationsStrategy in the short term is to focus on monitoring construction activity to ensure that codes are enforcedAll cost $ & we are seeking grants
47Quotations & Actions under Review Consultant review of siltation monitoring methods- Bathymetric survey entire lake +/- 1inch- Contours linked to sea level datum- Interface with dredging contractor drawingsConventional survey of Kahn pond with lake downMonitoring of construction discharges- 2 x private consultants- US Geological Survey Dept
48Do Private Lakes Provide a Public Benefit ? Capture storm water run-offReservoir for intense rain eventsRepository for silt, trash & pollutionAttract wildlife to urban areasAesthetically pleasing to residentsPrivate lakes deserve public funding support