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Notification#1600-2018-0116-R3 Streambed Alteration Agreement Page 3 of 16 Deepwater Channel (from 5-Star Marina on north side of channel or from Stockton Downtown Marina on the south side of the Channel). To utilize the mud rotary drilling operation, water would be drafted onsite from the Stockton Deepwater Channel. Construction Methods- Barge-Mounted Geotechnical Investigation'. In a "mud-rotary" or "rotary wash" drilling operation, mud (a mixture of water and bentonite) circulates through the borehole or outer casing, bringing the soil cuttings to the surface. A bit is connected to a series of"drill rods" that are attached to the drill head. The mud circulation system draws in the mud from a "mud tank" and sends the mud under pressure through the top of the drill head and down the inside of the drill rods. After the mud is discharged from the bit, the mud picks up the soil cuttings and carries them upwards between the drill rod and the sides of the borehole or between the drill rod and the outer casing. At the top of the hole, the mud pours out through a catch screen and back into the mud tank or a settling basin. In areas of cohesion-less soils or highly erodible soils, an outer casing is used to contain the drill rods, creating a closed circulation system. The casing is advanced concurrently with the drilling until it is seated in dense, un-erodible soils or bedrock. The mud tank serves as a settling tank for the cuttings, which will be periodically drained and the contents placed in 55-gallon steel drums. For Stage 2 drilling work at the Stockton Deepwater Channel, the drill rig and mud tank circulation system would be placed on a barge. Once the desired boring depth has been reached, the borehole will be flushed with clear water to displace the drilling fluid back into the mud tank. The drilling fluid and water will then be pumped from the mud tank into 55-gallon steel drums that will be removed from the job site and transferred to an appropriate staging area, usually a nearby Caltrans Maintenance yard. During barge- mounted drilling, water would be drafted onsite (pumped from the channel) from the Stockton Deepwater Channel. Caltrans will comply with water drafting specifications issued by California Department of Fish and Wildlife (CDFW). Water drafting will not introduce foreign water into the Stockton Deepwater Channel. The boreholes drilled in the Deepwater Channel will be backfilled with bentonite chips, cement grout, or other backfill as specified by regulatory agencies. The bentonite chips would be dropped through the outer casing and into the borehole. The bentonite chips swell rapidly upon contact with the water, filling the borehole. The bentonite chips will be left to expand in the borehole for approximately 10-20 minutes before the drill rod and outer casing is removed from the borehole. A typical core drill string is a series of connected long hollow drill rods with a barrel at the end connected to a special cutting bit (drill head) at the bottom of the hole. As the drill moves further into the earth, the driller adds rods onto the end, lengthening the drill rod string. As the driller rotates the drill rod, downward pressure and abrasion from the drill head cuts into the rock, pushing core into the core barrel (also called a "punch-core barrel"). This process creates a lot of friction and heat, so a flushing medium (in this case, the mud circulation system) is used to cool the bit, lubricate the core, remove the loose bits of rock (called the cuttings), and help stabilize the hole. When the driller