BEsT MANAGEMENT PRACTICEs HANDbooK - Tahoe BMP

8.9 DREDGING8.9.1 OVERVIEWDredging consists of an excavation operation carried out at least partlyunderwater, most often in shallow water areas with the purpose of gatheringup bottom sediments and disposing of them at a different location. Dredging isdefined in the Lake Tahoe Region as removing or rearranging earthen materialswhich are lakeward of the legal high water line (elevation equal to 6,229.1 feet).Dredging is generally prohibited by TRPA, with the exception of maintenancedredging. Maintenance dredging is the excavation of areas that have beenpreviously dredged to maintain authorized lake bottom elevations for boatnavigation. Maintenance dredging may be permitted in order to continue anexisting use, especially if required for navigational safety.Although quite rare, new dredging may be allowed for water intakes in LakeTahoe provided additional findings can be made regarding the need andpotential impacts. New dredging will lead to future maintenance dredging,thereby potentially increasing impacts to water quality in the long-term.The re-suspension of sediments during dredging operations raises concerns forwater quality. The CEM stresses careful selection of equipment combined withcare in operation to reduce potential impacts to water quality from dredging. 45General guidance for dredging, recommendations for mitigation measures,dredging methodology, and a description of environmental controls can befound in Impacts of Marina Dredging on Lake Tahoe Water Quality. 46Due to the potential environmental impacts, a number of federal, state andlocal regulations exist for dredging projects. These regulations lead torestrictions on the types of dredging allowed and the biological and waterquality monitoring required.The Lahontan Regional Water Quality Control Board (LRWQCB) adoptedstrict standards with the objective of minimizing short- and long-term waterquality impacts from dredging operations in the portion of Lake Tahoe underthe jurisdiction of the State of California. The Nevada Division ofEnvironmental Protection (NDEP) has adopted similar standards. In addition,TRPA has adopted specific ordinances regulating dredging operations in LakeTahoe. The intent of the ordinances is to prevent excess turbidity and thespread of surplus nutrients in the lake. Project proponents may determineapplicable regulations for their project through consultation with theInteragency Shorezone Coordination Group, a collaboration of agencies withjurisdiction in the Lake Tahoe Shorezone.45USACE, 2008, Coastal Engineering Manual - Parts I-646Tahoe Research Group, Goldman, C.R., Reuter, John E., Hackley, Scott H., 1996, Final Report,Impacts of Marina Dredging on Lake Tahoe Water QualityCHAPTER 8: Shorezone Protective Structures and BMPsTRPA BMP Handbook8.9 Dredging 2012Page 8-58