TRM called on for erosion control in reconstruction of St. Joe Road
By Jill Pack
As Tropical Storm Debby made its way to Florida in June 2012, residents prepared for the power outages, supply shortages, and flooding that typically accompany storms of this predicted magnitude. As Debby made landfall, the heavy downpour saturated the west coast of the state causing severe erosion in many areas.
When the slow-moving storm dissipated, it left behind an estimated $250Â million in damages across three states. Following the storm, President Obama issued a disaster declaration for 22 of the 67 counties in Florida. Severe flooding damaged thousands of homes, opened up sinkholes, and washed out roads.
Some roads turned into rivers, compromising local thoroughfares across the state. Once the water subsided, the state had to analyze the damage and create a plan to move forward with repairs.
One affected area was in Florida’s west-central Pasco County, where officials were forced to shut down roads until repair crews could access the area. This included St. Joe Road— also known as County Road 578, a vital connection heading west from Dade City—where the slope of the road was washed away and both the drainage system and guardrail were damaged.
Prepping for the aftermath
The Federal Emergency Management Agency (FEMA) approved up to $200,000 in emergency funding to repair the portions of St. Joe Road that were closed off. Officials estimated that the road would be closed for at least a month, according to the Tampa Bay Times.
Throughout the area, damage to private property totaled $1.5Â million, while public property losses were estimated at $26Â million, so projects of this nature were key to the restoration of the area after the storm.
To address the roadway challenges and erosion concerns, a group of certified engineers, planners, and surveyors who manage major development and transportation projects in the Tampa Bay area was contacted for support.
It was clear that the solution needed to provide green vegetation and greater slope protection for St. Joe Road. Engineers inspected the area to evaluate the situation. During their visit, they observed the severe erosion caused by Debby’s heavy downpours.
The project would be challenging because of several variables. The road had drastic elevation changes caused by previous erosion and the area that needed major repairs was located in one of the lowest points. It was also obvious that the adjacent stormwater system was designed to funnel water runoff to this area.
Because of these challenges, the engineers and consultants called for a more permanent slope protection product, with a better functioning drainage system.
A hard armor system was considered. However, the county wanted the landscape to be restored to its original vegetated state and this option would not support plant life after installation.
With the environmental requirement in mind, all possible vegetation-compatible systems were considered. A turf reinforcement mat (TRM) was identified as part of the solution. This environmentally friendly alternative to 30-in., or larger, rock riprap is suited for severe erosion control projects.
TRMs are ideal for high-flow channels, stream banks, shorelines, and other areas needing permanent vegetation reinforcement and protection from water and wind.
The TRM’s heavyweight polypropylene netting structure provided a stable reinforced base for the sod and plants placed on top of the mat. The roots of the vegetation grow through the 3-D mesh locking the roots to the face of the slope, while a coconut fiber matrix provided surface protection from erosion and moisture retention until full vegetation was established.
Before TRM installation could begin, the landscape contractor had to put up with more rain, which added to the numerous previous washout repairs on the unprotected slope. Once there was a break in the weather, the contractor began installation and repairs.
Installation of 4,000 square yards of the TRM took about three days on the 2:1 slopes, which were more than 60 feet long in some sections. The first sod was laid on the third day of the project and the job was completed ahead of schedule. The prompt completion also allowed St. Joe Road to open ahead of the date that city officials had originally predicted, always good news for local citizens.
The successful application was tested shortly after the project was completed because the area sustained another heavy rainstorm with a large amount of precipitation in a brief period of time. The TRM was successful in providing surface protection of the slope to prevent further erosion and it held the newly placed sod securely.