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HomeMy WebLinkAboutNotice of Intent to Adopt Mitigated Negative Declaration - Laguna Lake Dredging and Sediment Mgt Projectcoj_^U�vy\&*�I MI -111-1 i CITY OF SHII LUIS OBISPO Notice of Intent to Adopt Mitigated Negative Declaration (ENDORSED) FILED SEP 1 5 2017 TOMMY GONG, COUNTY CLERK Julianne Goble DEPUTY CLERK The City of San Luis Obispo has completed the Draft Initial Study/Mitigated Negative Declaration (IS/MND) for the proposed Laguna Lake Dred -gin -and Sediment Management Project. The IS/MND found the following environmental factors to be less than significant with mitigation incorporated: Air Quality, Biological Resources, Cultural Resources, Geology/Soils, Hazardous Materials, and Hydrology / Water Quality. The project is located at the Laguna Lake Natural Reserve at 504 Madonna Road, San Luis Obispo, CA 93401. The project site is not included on any of the lists enumerated under Section 65962.5 of the Government Code. The City of San Luis Obispo proposes to implement a maintenance dredging regime that will remove sediment impacting the function and operation of Laguna Lake (the "Lake") as a recreational facility within the Parks and Recreation Department and as a wildlife and natural reserve overseen by the City's Natural Resources Program. This work will be performed by hydraulic dredging methods without draining the Lake. The project also includes some elements of bank restoration and stabilization on the northern shore adjacent to the Park, emptying and restoring of the sedimentation basin on Prefumo Creek between Los Osos Valley Road and Laguna Lake, and future construction of a new sedimentation basin within the City owned golf course on the south side of Los Osos Valley Road on Prefumo Creek. The project will remove a sediment layer averaging approximately 3-4 feet deep in the area shown on Attachment 2 for a total removal of between 3,000 CY and 4,000 CY of material. The material will be disposed of at a local off-site location in a legal and lawful manner. Sediments will be transported to the disposal site in covered trucks/trailers. Although there may be one or more local ranches or development project sites that may desire and receive some or all of the sediment, the guaranteed or default disposal site will be the Cold Canyon Landfill, located at 2268 Carpenter Canyon Rd, San Luis Obispo, CA 93401. The landfill has reviewed the soils reports and determined they can receive the sediment for disposal, and possibly for use as daily cover dirt. The project will only dispose of sediment at other, closer locations if, at project bid time, these locations have appropriate and required environmental documentation and permitting in place. The area to be dredged extends from the outlet of Prefumo Creek downstream approximately 1,200 feet. The work will be performed within the Lake while it retains the water in it at the time of construction. The necessity for dredging and the associated public benefits of dredging include: 1. Restoring recreational use of Laguna Lake. Formerly a popular kayaking, canoeing, sailing and windsurfing lake, the Lake is now shallow and limited in its ability to support these activities. 2. Restore lake water quality and health of the lake to support birds and wildlife. The shallow lake creates a warm -water environment that is susceptible to seasonal algae blooms resulting in lower dissolved oxygen levels, decreased recreational use due to presence of microcystins, and more frequent dry cycles on the banks or lake -wide that create vegetation and fish die -offs, with associated decomposition odors and increased nitrate levels. 3. The Lake provides some natural flood protection as a natural water body, but is not maintained or operated as a flood control facility. The ability of the Lake to continue to perform its natural, limited function of flood control and water storage will be restored with dredging. 4. Deeper waters may support and enhance salmonid and other fish populations. The maintenance dredging regime is expected to be ongoing, but comprised of at least four construction seasons, avoiding the winter months between November 1 and April 15 to: 1) Avoid impacts during the wettest seasons on local wildlife and 2) Complete work outside the bird nesting season. To minimize impacts on local structures and citizens: 1. There will be no downstream releases of water. 2. Most access for work shall be from the north (park) side of the lake utilizing the park entrance on Madonna Road. 3. All dewatering of the dredged slurry soil will be performed by the following method: a. Semi -Passive Dewatering. Dredged slurry will be pumped onshore into geotextile bags or "tubes" that serve to decant the water through the fabric leaving the solids inside the geotextile bags. Flocculating polymer agents will also be used in conjunction with this process to more thoroughly remove turbidity. The geotextile bags will be placed into a sediment basin constructed a minimum of 100 feet away from the lake surface to allow for capture of materials and filtrated recharge into the soil profile. During this dewatering process, water quality will be improved from that of the existing lake water; nitrates and biocides (pesticides) tend to adhere to sediments. To assure that water quality meets established standards, a water quality testing program will be implemented during dredging. Trailer mounted activated carbon filters will be available for initial operations as a confidence measure for compliance, but will only continue to be used if on-going dredging operations and proposed dewatering equipment cannot satisfy permitting agency water quality requirements without them. 4. Water quality impacts by the dredging process will be mitigated by: a. Use of sediment screens to reduce migration of turbidity caused by the hydraulic dredging process, b. Dewatering processes designed and proven to treat the return water to an equivalent, or better water quality as proscribed in final permits. c. Sediment management plan with best management practices implemented at the dewatering and bank restoration and protection sites. The dewatering and sediment handling area will be as small as practical (approximately 3 to 4 acres), and contained within the area shown on Attachment 3. Material -shall be loaded on haulers or dump trucks, and hauled to the disposal site via City and County streets, as well as Highway 227. Equipment may include any or all of the following: One (1) tracked high-capacity (4-7 CY) excavator used to prepare the sediment basin area. Caterpillar 325 Excavators or equivalent (Diesel). • Two (2) front-end loaders (4-7 CY) (Diesel) used to load dewatered sediment into dump trucks. • Two (2) three—axle dump trucks, Cat CTC660 or equivalent (Diesel). • One (1) Oiler Truck, on a one ton Ford Frame, or equivalent (Diesel). ■ One (1) Water Truck/Trailer, on a one ton Ford Frame, or equivalent (Diesel). • Pontoon -boat mounted hydraulic 6" or 8" dredge that can be launched from the existing boat ramp, and associated floating 6" or 8" dredge pipe leading from the dredge to the dewatering site. Hours of operations will be between 7:OOAM-7:OOPM Monday through Friday and, if required, Saturday between 8:OOAM-5:OOPM. Once dredging activities conclude, the impacted areas of the park will be planted and/or seeded per pre -construction conditions and in accordance with final permits. With the exception of periodic sediment removal from the sedimentation basin on Prefumo Creek north of Los Osos Valley road, a sediment removal project has not been performed in the Lake since the early 1960s. Based on historic sediment flows and accumulation, and the anticipated development and maintenance of the sedimentation basin, it is estimated that a maintenance dredging regime project will need to remove approximately 3,000 to 4,000 cubic yards of sediment on an annual basis. The dredging priority area will be near the outlet of Prefumo Creek into the Lake where sediment deposition has been the greatest. Reference copies of the Mitigated Negative Declaration are available at the City's Clerk's Office, at 990 Palm Street, or by calling Robert Hill at 805-781-7211. These documents will also be available on the City's website at www.slocity.org. The required 30 -day public review period for the Mitigated Negative Declaration will extend from Friday September 15, 2017 to Tuesday October 17, 2017. Anyone interested in commenting on the document should submit a written statement to the City of San Luis Obispo, 990 Palm Street, San Luis Obispo, CA 93401, Attention: Robert Hill, Natural Resources Manager, or by email to rhill@slocity.org by 5:00 p.m., October 17, 2017. The San Luis Obispo City Council will hold a public hearing on October 17, 2017 to consider the adoption of the Mitigated Negative Declaration. Interested persons can access the City Council agenda at littp //www.slocity.org/governmentlmayor-and-city-council/agendas--and-minutes to locate the dates of the public hearings for this project. OCT 13 2017 CITYOF SHIM, LUIS OBISPO Notice of Intent to Adopt Mitigated Negative Declaration FILED OCT 13 2017 Ta�At r+L�, coUNTr CLE The City of San Luis Obispo has completed the Draft Initial Study/Mitigated Negative Declaration (IS/MND) for the proposed Laguna Lake Dredging and Sediment Management Project. The IS/MND found the following environmental factors to be less than significant with mitigation incorporated: Air Quality, Biological Resources, Cultural Resources, Geology/Soils, Hazardous Materials, and Hydrology / Water Quality. The project is located at the Laguna Lake Natural Reserve at 504 Madonna Road, San Luis Obispo, CA 93401. The project site is. not included on any of the lists enumerated under Section 65962.5 of the Government Code. The City of San Luis Obispo proposes to implement a maintenance dredging regime that will remove sediment impacting the function and operation of Laguna Lake (the "Lake") as a recreational facility within the Parks and Recreation Department and as a wildlife and natural reserve overseen by the City's Natural Resources Program. This work will be performed by hydraulic dredging methods without draining the Lake. The project also includes some elements of bank restoration and stabilization on the northern shore adjacent to the Park, emptying and restoring of the sedimentation basin on Prefumo Creek between Los Osos Valley Road and Laguna Lake, and future construction of a new sedimentation basin within the City owned golf course on the south side of Los Osos Valley Road on Prefumo Creek. The project will remove a sediment layer averaging approximately 3-4 feet deep in the area shown on Attachment 2 for a total removal of between 3,000 CY and 4,000 CY of material. The material will be disposed of at a local off-site location in a legal and lawful manner. Sediments will be transported to the disposal site in covered trucks/trailers. Although there may be one or more local ranches or development project sites that may desire and receive some or all of the sediment, the guaranteed or default disposal site will be the Cold Canyon Landfill, located at 2268 Carpenter Canyon Rd, San Luis Obispo, CA 93401. The landfill has reviewed the soils reports and determined they can receive the sediment for disposal, and possibly for use as daily cover dirt. The project will only dispose of sediment at other, closer locations if, at project bid time, these locations have appropriate and required environmental documentation and permitting in place. The area to be dredged extends from the outlet of Prefumo Creek downstream approximately 1,200 feet. The work will be performed within the Lake while it retains the water in it at the time of construction. The necessity for dredging and the associated public benefits of dredging include: 1. Restoring recreational use of Laguna Lake. Formerly a popular kayaking, canoeing, sailing and windsurfing lake, the Lake is now shallow and limited in its ability to support these activities. 2. Restore lake water quality and health of the lake to support birds and wildlife. The shallow lake creates a warm -water environment that is susceptible to seasonal algae blooms resulting in