TYLI provided design and environmental management for the Joint Venture Team of the $80 million dredging and disposal operations of approximately 721,000cy of contaminated sediment from the lower 5.7 miles of the Miami River. The project involved the dredging, materials handling, transport, and disposal of sediments from Miami River extending from Biscayne Bay northwest to the South Florida Water Management District (SFWMD) salinity dam (S-26). The Miami River is a narrow shipping corridor with substantial maritime traffic, 42 utility crossings and 13 bridges. This portion of the Miami River is within the Biscayne Bay Aquatic Preserve, an environmentally sensitive Outstanding Florida Water (OFW,) and the dredging and disposal operations were conducted according to stringent environmental standards.
The objective of the Miami River Maintenance Dredging Project was to restore the channel to the required depth of -15 ft mean low tide and included both the Federal Channel and the Non-Federal Channel (“Bank-to-Bank”). The design section width varied from approximately 100 ft in the upstream reaches of the project area to 200 ft in the vicinity of Biscayne Bay. Dredge material removed from the river underwent a sand separation and dewatering process to reclaim “clean” sand for beneficial reuse.
For this project TYLI provided engineering design support and construction environmental oversight for the dredging and disposal operations. TYLI coordinated permits and design documents for both the dredging operations and sediment treatment system with the USACE, FDEP, DERM, and county building department. Permit/plan requirements were coordinated with the agencies in order to accommodate dredging while minimizing impacts to the surrounding environment. Coordination also needed to occur with other activities requiring approvals or permits such as utility relocations, disposal of the sediments, and contractor staging areas.
Dredge material processing involved various phases of sand separation and dewatering to reclaim sand for beneficial reuse as landfill cover: 1. Physical separation by screens; 2. Physical separation by hydrocyclone; 3. Chemical separation through the addition of cationic polymers and clarifiers, and 4. Dewatering by filter presses. As part of our services, the TYLI also prepared the Spill Prevention and Countermeasure Control (SPCC) Plans in compliance with 40 CFR Part 112 and designed the interim storage area for the sand separated from the dredge material processing plant prior to reuse offsite.
Water-related construction activities also took place in designated Critical Habitat of the West Indian manatees; therefore, consistent with the Manatee Protection Act, dedicated qualified endangered species observers were required to monitor for the presence of manatees during construction activities in the water. Although construction in manatee zones has generally been limited to daylight due to restriction placed on the manatee observers, TYLI was successful in gaining approval for the Miami River Dredging project to allow for manatee observers on a 24 hours per day, 7 days per week basis to enable nighttime construction activities and reduce the construction schedule.
Also since the project was within sensitive environmental areas, variances for several elements of the work were requested such as mixing zone and regulatory action levels for turbidity. TYLI successfully implemented water quality variances on the Miami River dredging project to reduce monitoring requirements. Surface water monitoring included low-tide compliance and trend sampling for the following parameters: Turbidity (in-situ), Dissolved Oxygen (in-situ), Biochemical Oxygen Demand (BOD5), total phosphorous, petroleum hydrocarbons, copper and lead.