Reso 2004-069 - Laserfiche WebLink

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PO"rE~IIAULY ISSUES s~c~incn~r ISSUES c. Be located on a geologic unit or soil that is unstable, or that would become unstable as a result of the project, and potentially result in on- or off-site landslide, lateral spreading, subsidence. liquefaction or collapse: d. Be located on expansive soil, creating substantial risks of life or property? e. Have soils capable of adequately supporting the use of septic tanks or alternative waste water disposal systems where sewers are not available for the disposal of waste water`? f. Any increase in wind or water erosion of soils, either on- or off-site? g. Changes in deposition or erosion of beach; sands, or changes in siltation, deposition or erosion which may modify the channel of a river or stream or the bed of the ocean or any bav, inlet or lake? ro~rE~~n,v.Ev SIC,AFICA~T LESS"r11AV ~~ UALESS SIG~'IrICA,A1~ 1~1PACT SOURCES ~7ITIGATI0A 1~1PACT I~CORPORA"rED ){ ~ 1, 4, 7 X ~ 1, 4, 7 X ~ Io X ~ ~ 1, '7 X ~ ~ 1, ~ EXPLANATION: a-g) The project site is comprised of compressible Bay mud. These sediments, especially for the more recently deposited sediments in the West Basin and in sub layers where the sediments are saturated, are unstable and would not support certain equipment. Equipment working in the area would be subject to sinking in the soft mud and could become fouled. The site has no known unique geological or physical features. The project would involve excavating and removing approximately 60,000 to 80,000 cubic yards of material, regrading the area and returning elevations so that the DMMS can better Function as shorebird habitat when not needed for dredge material placement. Therefore, the soil will experience disruption, displacement, compaction. and overcovering. General land use in the DMMS vicinity would not be altered by the project. The site would be seasonally flooded under optimal conditions to enhance its habitat value for shorebirds. The dried dredged material would be excavated, graded, and transported off-site to the Oyster Bay Regional Shoreline Park. This handling of the sediment may increase wind erosion of the soils. However, regular watering of all unpaved construction areas and haul routes would keep dust generation to a minimum. Any waterborne sediment would be contained within the levees and redeposited. No water would be released from the site except through established weirs under monitoring requirements of the Regional Water Quality Control Board. Maintenance dredging operations periodically introduce dredge slurry to the site containing approximately 20 percent solids (sediments). The suspended sediment then settles out and is dried and removed. "The decanted water is released to Estudillo Canal and ultimately into the Bay. Consequently, no substantial amount of sediment is or would be released from the site. No significant changes in deposition, erosion or siltation would occur in the Canal. The site is underlain by compressible bay mud, comprised of stiff silty clay and very stiff sand-clay deposits. The bay mud deposits have a high potential For earthquake-induced ground failure due to liquefaction. Also, very strong groundshaking would be anticipated in the study area from a major earthquake. While damage and injury could occur to construction workers during episodes of strong groundshaking, the project does not introduce any new structure that would increase the risk to workers if such an event were to occur during the construction period. Sa^ Leandro Dredged Material Management Site 4 ivtarcn i wvti Sediment Removal Project