The C.W. Bill Young Regional Reservoir is an off-stream reservoir used to store surface water for subsequent treatment and potable use. Skimming and storing water from three rivers during high-flow periods dramatically increases the sustainable yield of the surface water system, and helps meet the region’s drinking water needs.
The reservoir has a surface area of approximately 1,000 acres. An earthen embankment approximately 26,000 ft long surrounds the reservoir. The reservoir level is above the natural grade and was constructed of excavated onsite materials to form the embankment. The maximum depth of the water above the natural grade ranges from 22 ft at the southeastern corner to 57 ft in the northwestern corner. The storage capacity is approximately 15 billion gal.
The reservoir is designed with 8.5 ft of freeboard, which will allow for rainfall of 3.3 ft, plus 5.2 ft of wave run-up. The 3.3 ft of rainfall is the statistically probable maximum precipitation in Florida—more than the largest historical 24-hour rain event on record. The 5.2 ft of freeboard for wave run-up is calculated from the longest reservoir reach and during sustained winds of 110 miles per hour.
In addition, because the reservoir is an off-stream facility, additional actions may be made when extraordinary events, such as hurricanes, are expected. These actions may include ceasing water diversions to and/or removing water from the reservoir.
The management of the reservoir includes operation, maintenance, monitoring and security activities, including personnel on site 24 hours per day. A maintenance crew maintains the reservoir, and operations personnel conduct water sampling. Security personnel patrol the reservoir grounds continuously.
In addition, a third-party professional engineer conducts annual inspections. Instrumentation is installed in the embankment to monitor water levels and pore pressures. From this data, trends can be observed and addressed. This allows Tampa Bay Water to become aware of changes in embankment conditions early so that, if required, preventive maintenance can be used to mitigate problems.
Developing an emergency plan
While safety was considered in every step of the project from inception to operation, Tampa Bay Water recognized the need to be prepared for an emergency. HDR developed an emergency action plan (EAP) for this project.
The EAP is a formal document that identifies potential emergency conditions and specifies actions to be followed to minimize impacts. It contains procedures and information to assist Tampa Bay Water in issuing early warning and notification messages to responsible emergency management authorities of any emergency situations. The overall purpose of the EAP is to develop procedures and guidance to:
- Safeguard citizens living in areas that could be flooded should the embankment fail;
- Provide effective facility surveillance and prompt notification to local emergency management agencies; and
- Assign actions to be taken by Tampa Bay Water in the event of a potential or imminent failure of the reservoir’s embankment.
The EAP follows the guidelines provided by the Federal Emergency Management Agency (FEMA). These guidelines identify six basic elements that EAPs should include:
- Notification flowchart;
- Emergency detection, evaluation and classification;
- Inundation maps; and
Development of Tampa Bay Water’s EAP was based on reviews of Hillsborough County’s emergency management plans, FEMA guidelines and relevant agency rules and statutes. The EAP is reviewed and updated annually with a complete reprint of the document every three years. Local and state emergency management agencies will use the information in the EAP to help facilitate implementation of their specific responsibilities. This process includes coordination, planning, and joint exercises involving both the EAP of Tampa Bay Water, and warning and evacuation plans of local emergency management authorities.
Prior to filling the reservoir, the EAP was tested through a simulated exercise where all stakeholders (Tampa Bay Water, Hillsborough County Emergency Management, Hillsborough County Sheriff’s Office, and Hillsborough County Fire and Rescue) participated. The primary objectives of the exercise were to demonstrate the appropriate and realistic command and control activities, utilize the appropriate incident communications, demonstrate the appropriate public information actions and utilize the appropriate population protective actions. Overall, the exercise was a success, and all the stakeholders felt better prepared to respond in the event of an emergency at the C.W. Bill Young Regional Reservoir.