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<br />Types of Dredging <br /> <br />Types of Dredging <br /> <br />. Hvdraulic Dredqinq <br />- Employs a system of cutter head, water jets and suction lines <br />- Culler head and water jets loosen the sediment, fOrming a slurry <br />that is then vacuumed into the suction lines <br />- The slurry as low as 15% dredge material Is then pu~ed to its <br />desired Iocallon at the Clly's Dredge Material Management Site <br />(DMMS) <br /> <br />Aqitation Dredainq <br />- Boat with a modijied propeller, deflection shield or hydro <br />injection system <br />- Water is directed under high velocity at the sediment <br />- Sediment is agllated and saturated and is then transported by <br />the surrounding currents and sellles in adjacent areas <br /> <br /> <br /> <br />, <br />~. ~ <br />, :;;,.~~">, <br />~ ~ ,"'....- , ... <br />.i"v.;,"'..... <br /> <br />"I -.~_ <br /> <br />Types of Dredging <br /> <br />Dredge Material Disposal <br /> <br /> <br />. Upland Disposal <br />- Hydraulic dredge material pumped to DMMS <br />- Decanting of material <br />- Removal by excavator and trucked for reuse <br />In-Bay Disposal <br />- Dredge material placed directly Into barge <br />- Barge transports matertal and releases into bay at approved <br />location, Le" near A1catraz <br />- Earty dredging material disposed of in-bay near Marina until <br />stopped by regulations <br />Ocean Disposal <br />- Dredge material placed dlreclly on barge <br />- Barge transpOrts material to a location outside the Golden Gate <br />Brkfge Into the open ocean <br /> <br />Peak Trimminq Method <br /> <br />- Employs dragging a blade across the humps, trimming their <br />peaks and allowing the sediment to sellle in the surrounding <br />area <br /> <br />10 <br /> <br />DMMS <br /> <br />City's Dredging History <br /> <br />Upland Disposal Stte <br />formal]zed as the DMMS In 1992 to <br />meet Regional Water Quality <br />Control Board (RWacS) <br />requlrements <br /> <br />100 acres of managed habitat <br /> <br />Shorebird sanctuary ISland ]5 <br />established each time the site Is <br />graded <br /> <br />1960.61 <br />- Original mMna and channels <br />constructed at Clly's cost <br />- Channels dredged to a depth of -6 <br />Mean Lower Low Water (MLLW) <br />- Hydraulically dredged <br />- Material pumped to an adjacent water <br />area 1,500 feet south of and paralleling <br />the main access channel <br />- Marina berthing area dredged 10 a <br />depth of -5 MLlW at the east end to a <br />depth of -10 MLLW at the west end <br />- Material dredged from the auxiliary and <br />Interior channels was used for dike <br />construction and adjacent landfill <br /> <br /> <br /> <br />'- ~ '>. <br /> <br />\' ", ,~', <br />~~ :.~~~, <br /> <br /> <br />'<,4\ <br /> <br />11 <br /> <br />12 <br />