The Central Drainage Ditch (CDD) Watershed encompasses a majority of downtown Tallahassee and the Florida State University campus. This project was a joint venture between the City of Tallahassee and FSU. The objective of the project was to model the 5.5-square mile CDD watershed and to develop a regional stormwater facility which could maximize stormwater attenuation and treatment capacities to account for future development by both FSU and the City as well as address flooding concerns in the area.
SAI conducted comprehensive stormwater modeling of the CDD watershed, including model calibration and verification based on 4 historical storm events, 5 rainfall gages, and 4 continuous recorder stream gages. Modeling involved complex bridge structures and aerial utility crossings.
Using the model data, SAI developed the design of a 23-acre regional stormwater facility with a diversion berm, littoral zone, over 200-feet of 12'x10' concrete box culvert under a major 4-lane State roadway, and an intake structure with an inline floating skimmer and trash trap for collecting floating debris. The design also included channel improvements to the CDD, relocation of a 36" sanitary sewer aerial crossing, and nearly 1,000 feet of 30" sanitary gravity sewer. An area of petroleum contaminated soil was identified at the north end of the stormwater facility. The project was design and implemented in three phases to allow for the remediation of the contaminated soil. SAI conducted final engineering of the design, developed full construction plans, and successfully obtained permits from the FDEP and FDOT.