Sediment Loss Rate Clause Samples

Sediment Loss Rate. For the case of grab dredging at the middle CMP, there will be two dredgers working concurrently and continuously (i.e. 24 hr). Since the total production rate would be 100,000 m3/week, the individual working rate is about 297.62 m3/hr as a continuous sediment source. Sediment loss is assumed to be distributed throughout the entire water column. Sediment loss rate of 17 kg/m3 is assumed following the same assumption in the approved EIA of AEIAR-089/2005 New Contaminated Mud Marine Disposal Facility at Airport East / East Sha ▇▇▇▇ Area. The rate of release (in kg/s) of sediment for one dredger working at the above maximum rate is calculated as follows: 𝐿𝑜𝑠𝑠 𝑅𝑎𝑡𝑒 (𝑘𝑔/𝑠) = 𝐷𝑟𝑒𝑑𝑔𝑖𝑛𝑔 𝑅𝑎𝑡𝑒 (𝑚3⁄𝑠) × 𝑀𝑎𝑠𝑠 𝑜𝑓 𝑆𝑒𝑑𝑖𝑚𝑒𝑛𝑡 𝐿𝑜𝑠𝑠 𝑝𝑒𝑟 𝑈𝑛𝑖𝑡 𝑉𝑜𝑙𝑢𝑚𝑒 𝐷𝑟𝑒𝑑𝑔𝑒𝑑 (𝑘𝑔⁄𝑚3) = 0.0827 𝑚3⁄𝑠 × 17 𝑘𝑔⁄𝑚3 For the case of dredging with TSHD at the middle CMP, there will only be one TSHD working continuously. According to the approved EIA of New Contaminated Mud Marine Disposal Facility at Airport East / East Sha ▇▇▇▇ Area (AEIAR-089/2005), it is assumed that TSHD with ▇▇▇▇▇▇ size of 4,500 m3 would be used. Following assumptions adopted in AEIAR-089/2005, about 3,050 m3 of in- situ sediments would be removed in 20 minutes for each cycle. For this modelling study, it is assumed there will be 12 trips per day each last for 20 minutes and at 2 hours interval. The maximum total production rate would be 256,200 m3/week (3). Sediment release due to disturbance by the drag heads is assumed to be 7 kg/m3 dredged (4) (5). Sediment loss is assumed to be concentrated at the bottom of the water column. The rate of release (in kg/s) of sediment for one TSHD working at the above maximum rate is calculated as follows: 𝐿𝑜𝑠𝑠 𝑅𝑎𝑡𝑒 (𝑘𝑔/𝑠) = 𝐷𝑟𝑒𝑑𝑔𝑒𝑑 𝐼𝑛 − 𝑠𝑖𝑡𝑢 𝑉𝑜𝑙𝑢𝑚𝑒 𝑝𝑒𝑟 𝐵𝑎𝑟𝑔𝑒 (𝑚3) × 𝐿𝑜𝑠𝑠 𝑅𝑎𝑡𝑒 (𝑘𝑔⁄𝑚3) ÷ 𝐷𝑢𝑟𝑎𝑡𝑖𝑜𝑛 𝑝𝑒𝑟 𝑇𝑟𝑖𝑝 (𝑠) = 3050 𝑚3 × 7 𝑘𝑔⁄𝑚3 ÷ 1200 𝑠 Assuming a forward speed of 0.3 m/s during loading for the TSHD, the TSHD would move about 360 m forward in a 20-minute cycle. To capture this movement, the sediment source for TSHD would be modelled as a moving source along the northern part of the eastern edge of the key area for potential CMP development. Sediment load would be distributed in the corresponding model grid cell. For backfilling in the northernmost CMP, it is assumed each barge will be loaded with 800 m3 of sediment. TSHD could also be used as considered in AEIAR-089/2005, but it is expected to result in less sediment impact given the same disposal rate as sediment would be released at the lower pa...