Water: Nonpoint Source Success Stories
Florida Section 319 Success Stories, Vol. III
Forest Resource Administrator
Division of Forestry
Department of Agriculture and Consumer Services
11650 Munson Highway
Milton, FL 32570
|Primary Sources of Pollution:|
|roads (timber, recreational)|
|Primary NPS Pollutants:|
|redirection of water flow|
|reduced sediment delivery|
Blackwater River Restoration:
Project Demonstrates Mechanics of Erosion and Effectiveness of BMPs
Ever know of a natural area that the users "loved to death"? The Blackwater River and the adjacent Blackwater State Forest in the Florida panhandle are good examples. Primitive roads created for and by the timber industry and by recreational users, including canoeists, tubers, horse riders, and hunters, have led to serious soil erosion problems in the forest. Roads leading to or along the river and its tributaries have caused erosion in the sandy, exposed soils of the watershed and along the shoreline, resulting in heavy sedimentation to the river.
The Florida Division of Forestry treated 17 roads on the river's south side, closing 14 and repairing three. Methods of closing and repairing the roads varied depending on the slope, likelihood of continued traffic, natural stabilization mechanisms in place, sources of water creating the erosion, and suitability of the best management practices (BMPs). The objective in each case was to remove or redirect the source of water flow causing the problem and to stabilize the soil. The overall project cost was $55,928, of which $25,268 was provided by a section 319 grant to the Florida Division of Forestry.
Despite willful damage to treated areas by locals (subsequently repaired), the project was considered a success because sediment production from the roads was reduced and the restored areas were returned to timber production. The project taught the forest staff that soil cover is the key to reducing soil loss. The cover can be in the form of erosion fabric, vegetation, or mulch. Permanent native vegetation is expensive to procure, especially for large restoration areas. To continue this type of work on a forest-wide basis and make a significant impact on the soil erosion problems at a reasonable cost, some other means of revegetation will need to be used. The forestry staff believes transplanting forest materials will be one of the solutions.This demonstration project helped state foresters better understand the causes and mechanisms of erosion and sedimentation. Just as important, the project allowed the foresters to learn more about the effectiveness of BMPs that can be used to minimize erosion problems and where various BMPs work best. Consequently, state foresters have developed a management plan to continue addressing the erosion problems resulting from dirt roads and gullies that are negatively affecting the quality of the Blackwater River, an Outstanding Florida Water. Implementation of the management plan is proceeding using a variety of funding sources, including section 319 grants from the Florida Department of Environmental Protection, state funds, user fees, and in-kind contributions by forest users.
Brevard County's Urban Storm Water Retrofitting Projects:
Brevard County has implemented a storm water utility fee to help fund retrofitting projects, and its storm water program has initiated several projects leading to a reduction in the pollutant loadings discharged to the lagoon. The county has received a number of section 319 grants to assist in funding these projects. The costs of the retrofitting projects are provided in the table.
Retrofitting Project Costs
Indialantic area retrofitting
Several storm water retrofitting projects have been conducted in the town of Indialantic to reduce pollutant discharge to the Indian River Lagoon. The first phase of retrofitting involved the installation of numerous baffle boxes (sediment boxes) at the end of existing storm drain pipes to capture sediment before it is discharged. The frequency of cleanout depends on rainfall frequency, land use, and drainage basin size but has averaged six cleanouts per baffle box per year. The maintenance records for 24 baffle boxes show that 202 cubic meters of sediment were removed from these boxes over a 3-year period.
Later phases of retrofitting in this area focused on treating storm water from an urbanized residential watershed of 120 contributing acres. The best management practices installed to correct storm water quality and quantity problems included construction of an exfiltration trench that discharges to a wet detention pond. The pond was planted with cordgrass and pickerelweed to provide nutrient removal and cattail control. The new sideslope Geo Web cells were planted with blanket flowers and sunflowers for additional erosion control.
Based on Florida's rainfall records and the design treatment volume of the exfiltration system, it is removing about 60 percent of the pollutants that would have been discharged. Water quality sampling of several storm events showed that the pond is providing significant treatment of storm water pollutants through settling and biological processes. Overall, the treatment system appears to be removing most nutrients, metals, and suspended solids from the storm water before discharge to the Indian River Lagoon.
Micco area retrofitting
The Micco area of Brevard County is an urbanized single-family residential area that was built before the storm water treatment requirements. The area's existing storm water system provided no treatment of the area's runoff, which was discharged to the Sebastian River and ultimately to the Indian River Lagoon. Prior to this project, Main Street ran directly down to its lowest point at a boat ramp. Because there were no curbs or gutters, storm water ran down the edges of the pavement, causing considerable erosion and transporting a lot of sediment into the river.
To arrest the direct discharge of storm water, the county developed a trench system designed to remove sediments. The county installed 1,536 linear feet of exfiltration trenches down the center of the road along with asphalt curbing to direct flow to inlets installed along the road's edge. The trenches capture 0.39 inch of runoff from the 15.5-acre watershed, and pretreatment is provided by sumps and skimmers at the inlets.
For a variety of reasons, monitoring on this project proved to be problematic. However, maintenance activities were able to document the effectiveness of the trench system in removing sediments. The inlet system was cleaned twice during the postconstruction monitoring period, and a total of 14,076 pounds of sediment was removed. In addition, based on Florida's rainfall patterns and the diversion of runoff into the trenches, it is estimated that the system removes 80 percent of the pollutants that previously were discharged to the Sebastian River.
Lessons learnedMany valuable lessons were learned from this project related to design, location, and monitoring. Brevard County staff are applying this information to current and future projects designed to address water quality and quantity problems throughout the Micco watersheds. Other local governments in Florida also are benefiting from the project as they develop and implement storm water master plans to reduce storm water pollution.