Novato Creek Maintenance Sediment Removal & Wetland Enhancement (Lake or Streambed Alteration Agreement No. EPIMS-MAN-56012-R3)

Novato Creek Maintenance Sediment Removal & Wetland Enhancement (Lake or Streambed Alteration Agreement No. EPIMS-MAN-56012-R3)

The California Department of Fish and Wildlife (CDFW) has executed Lake and Streambed Alteration Agreement (EPIMS-MAN-56012-R3), pursuant to Fish and Game Code section 1602, to the project Applicant, Marin County Public Works. The Project is limited to dewatering and removal of accumulated silt and sediment from the beds of Novato, Warner, and Arroyo Avichi creeks, and placement of removed sediment on top of the levees that surround the Lynwood Basin. The majority of the removed sediment will be used for an active separately permitted restoration project, Agreement No. EPIMS-MAN-42501-R3 (Restoration Project). Removed sediment not used in the Restoration Project will be beneficially used as a thin-lift placement on an ecotone levee within Deer Island Basin surrounded by wetlands adjacent to Novato Creek. Any remaining removed sediment will be temporarily stockpiled for later use for the Restoration Project, the ecotone levee, or for use at the upland sites described below. This Project is associated with two expired previous streambed alteration agreements, 1) 1600-2011-0409-R3 (a routine maintenance agreement) which allowed for sediment removal within the same creeks described above, and placement of removed sediment on the surrounding Novato Creek levees as reinforcement, and 2) 1600-2016-0118-R3 which allowed for the placement of removed sediment from Novato Creek within the North Deer Island Basin to construct a new levee core, culvert replacement at an existing cross levee, placement of removed sediment within Heron’s Beak Pond, and bank stabilization improvements to an existing levee bank. Permittee also has a separate active Long-Term Maintenance Agreement No. 1600-2021-0018-R3 covering the Project area for vegetation management, limited sediment and debris removal from around and within structures, repairing and stabilizing levees, and other activities. Dewatering activities include using a total of three cofferdams, two will be installed at the upstream end of the work area of Warner and Novato creeks, and one cofferdam will be installed at the downstream end of the work area of Novato Creek. Arroyo Avichi Creek is expected to be dry during work periods, as it has been during previously permitted activities. Residual upstream freshwater flows from Novato and Warner creeks will be collected and conveyed to Lynwood Basin via existing underground drain lines and temporary aboveground bypass pipes. Sediment removal activities include the removal of approximately 6 to 18 inches of accumulated gravel and sand materials from the beds of upper Novato, Warner, and Arroyo Avichi creeks, and removal of approximately 1 to 3 feet of accumulated sand and clay silt material from the bed of lower Warner and Novato creeks. Sediment removal will be performed using draglines, excavators, dozers, and dump trucks. The estimated volume of sediment to be removed is approximately 36,775 cubic yards (CY), with approximately 14,000 CY placed on the ecotone levee; placement height ranging from six inches on the low side graduating to 24 inches on the high side. As described above, any excess sediment not reused in the Restoration Project or ecotone levee would be temporarily stockpiled at the upland sites for later use: Duck Bill Levee with up to 6,000 CY, Lynwood Levee up to 10,075 CY, or Hanna Ranch Road up to 6,700 CY. A maximum of 22,775 CY will be stored on these sites and sediment stockpile heights will not exceed 4 feet at any of the locations. Following the sediment removal, a low flow channel will be created (3 to 6 feet wide and 1 foot deep) to provide for concentrated low flows and fish passage. Sediment removal will take place within the dewatered footprint areas resulting in the same temporary impacts with no increase. The Project will result in a total of 26.81 acres (1,167,877 square feet (SF) and 8,196 linear feet (LF)) of temporary impacts to stream habitat as described below: 1) 11.79 acres (513,572 SF and 8,090 LF) associated with dewatering and sediment removal 2) 0.22 acres (9,583 SF and 106 LF) associated with cofferdams 3) 3.20 acres (139,392 SF) associated with the thin-lift placement on the ecotone levee 4) 2.60 acres (113, 256 SF) associated with stockpiling on the Duck Bill Levee site 5) 8.20 acres (357,192 SF) associated with stockpiling on the Lynwood levee site, 6) 0.80 acres (34,848 SF) associated with stockpiling at the Hanna Ranch Road site The Project will not result in permanent impacts to stream habitat. Equipment will access the channels, where possible, from previous access locations where vegetation is already disturbed and sparse, and only the minimum amount of vegetation clearing required will be implemented, no trees will be removed. After dewatering and sediment removal are completed, all temporary cofferdams and associated fill will be removed, and the channels will be restored to pre-Project conditions. The Project will not result in permanent impacts.

Novato

Marin

San Francisco Bay Area

Marin