Jacksonville, Duval County30.32688700, -81.87867300
Stormwater improvements included roadway reconstruction, roadside conveyance improvements and downstream channel improvements to alleviate flooding and prevent roadway overtopping for the 100-year, 24-hour and the 25-year, 24-hour design storm events. Along Old Plank Road, the roadway was reconstructed in targeted areas to raise the profile, preventing overtopping.
The project is located along Old Plank Road west of Halsema Road and east of Bea Lane in the west side of Jacksonville. Old Plank Road is a two-lane road and categorized as a collector road. The purpose of the project was to reduce existing flooding of Old Plank Road and adjacent properties through the implementation of stormwater structural improvements and the creation of an 8.5-acre wetland area.
During moderate storm events, the roadside ditches would flood and overtop the roadway, preventing suitable access along Old Plank Road. Emergency services cannot provide adequate service to multiple residential properties in this area, creating an unsafe condition during critical storm events. Many residents adjacent to Old Plank Road have also stated that their property floods during these storm events.
Waterbodies impacted: Brandy Branch and McGirts Creek
Flood control elements
Conveyance improvements along Old Plank Road included replacing existing side drains with larger side drains. Pipe end treatments with side drain mitered ends, where feasible, improve roadway safety. The roadside ditches were regraded. Additional cross drains were constructed east of Bea Lane and at the unnamed road to prevent roadway overtopping on the upstream (southside) of the road. The existing 53″x34″ pipes were replaced to provide better conveyance under Old Plank Road.
Within the downstream existing COJ drainage easement (tributary to McGirts Creek), a 15 feet wide bottom width drainage channel with a 20 feet wide maintenance berm was constructed south to the Jacksonville-Balwin Rail Trail. The channel was connected to the proposed 8.51-acre wetland creation area on the east with three 18″ pipes to allow water to equalize and utilize storage in the proposed wetland creation area.
The proposed wetland creation area will remain dry in its natural condition and provide additional storage to the drainage channel during higher storm events. Three 42″ pipes bleed down the channel to allow it to drain after storm events without causing adverse impacts downstream. Four 43″x 68″concrete box culverts were constructed under the maintenance berm to allow flows to the northeast to the remaining portions of the large wetland system. A concrete overflow weir was constructed to avoid stage increases for larger storm events.
Stormwater Master Plan
The project is not specifically listed in the 2011 City of Jacksonville Stormwater Management Plan Update, but the basin that the project is in is the basin (Ortega basin) in the plan and recommended for drainage improvements.
McGirts creek is located in the Lower St. Johns Main Stem BMAP. The project is located in the McGirts Creek waterbody (WBID#2249B) which is a tributary of the Ortega River that discharges into the Lower St. Johns River. McGirts Creek is a Class 3F stream. While McGirts Creek does not yet have its own TMDL, it is included as a load contributing waterbody for the lower St. Johns Main Stem BMAP allocations to the City of Jacksonville NPDES MS4. McGirts Creek itself is not impaired for nutrients; however, it can improve water quality in the St. Johns Main Stem and help to meet the BMAP goals.
The wetland creation area is used as an education component of the park. An interpretive sign and trail is planned but has not been built yet. The Parks department is meeting with the City wetland subcontractor to help with the interpretive sign language.
This project protects 34 acres and 41 properties that experience flooding during normal storm events. There are 92 acres of onsite basins including areas draining to roadside ditches and the limits of the outfall ditch and wetland creation area. There are 1,310 acres of offsite basins that includes areas that eventually drain to the outfall ditch in which some of the areas have onsite storage/treatment.
The City will conduct qualitative vegetative and hydrologic monitoring of the wetland creation area for five years. Monitoring will be performed on a bi-annual basis. If the restoration area is trending toward success after the initial three years, monitoring events will be reduced to one event per year in the fall. The City will establish belt transects, including all representative vegetative communities, to allow for the assessment of the overall survivorship and health of the planted trees.
A fixed photo station will be established for annual photo documentation. In addition, the Old Plank Road area will be monitored after 25YR/24HR storm and other smaller storm events that typically cause roadway over-topping. The City complaint system will monitor any flooding complaints for this project area.
Annual cost: $4,000
Project Cost & Funding
Total Project Cost: $4,376,125
Total Construction Cost: $3,724,232
A public meeting was held for the residents of the Old Plank Road area on May 9, 2011 and was attended by over 30 residents interested in the project. During the meeting, residents provided photos of flooding and comments on the flooding that have occurred on their properties.
The wetland creation area Is used as an education component of the park, and an interpretive educational sign was installed and adjacent hiking trails were constructed around the wetland creation area.
Outcomes & Results
Water quality/quantity benefits: 42.9 lbs./yr. of TN and 8.4 lbs./yr. of TP, 34 acres protected from flooding, 8.51 acres of wetlands restored/enhanced wetland acres created
The City did receive some complaints from nearby residents soon after the construction completion concerning structure flooding. The flooding did occur after a 100-year storm. The flooding was investigated, and the City believes the flooding was the result of the over 100-year storm event that occurred. The RWSM Division cleaned out the waterway after the project which may have solved the flooding issue also. The City has not received any complaints since that period a couple of years ago.
Volume 10 Ortega basin Section 2.0