The area of Vanderbilt Drive Cul-de-sacs is affected by several issues during a rainfall event. The goal of the stormwater improvement project is to decrease the depth of roadway flooding and the time (duration) that stormwater runoff inundates the roadway. No stormwater improvement project “floodproofs” a neighborhood. Below are a few additional informational facts provided to help residents better understand the expectations of the ongoing work.
- High tide conditions at the stormwater outfall (the downstream-most section of the system) restrict the rate at which stormwater can discharge from the area. The neighborhood will drain slower during periods of high tide. This was a pre-project condition, is a condition during construction and will remain a limitation post project completion. This is a condition common to many neighborhoods that were constructed in the 1950’s, 60’s and 70’s near the water’s edge with minimal stormwater management infrastructure. Modern stormwater management design and regulations were not implemented in South Florida until the late 1970’s.
- The neighborhood is surrounded by the Vanderbilt Lagoon and elevations of portions of the existing roadways that flood during summer rainfall events are only a few feet above sea level. The entire area can be flooded if a major storm delivers several inches of rain in a short period of time. Older homes were not required to be elevated as new homes currently are. Current building code requires that the living level of all new homes are built at or above the required base flood elevation (FEMA NFIP – Federal Emergency Management Agency National Flood Insurance Program Flood Mapping and Risk Analysis).
- Upon completion of the stormwater improvements, streets will still flood during intense rainfall events. Neighborhood conditions discussed above limit what can be done with the performance of the system. If this neighborhood was constructed today from original undeveloped land the roads would be several feet higher. Elevating the existing roadways today is not
Specific stormwater management challenges and stormwater system improvements related to Vanderbilt Drive and Conners Subdivisions are further described below.
Conners Subdivision
Challenges
Stormwater management system improvements are currently being completed as part of the Collier County Public Utilities Renewal Program along the fourteen (14) cul-de-sac streets in the Conners subdivision.
This subdivision was designed and built prior to modern stormwater management regulations and practices. Since there are no existing common areas designated for stormwater management in the neighborhood, all collection, conveyance, and treatment of stormwater runoff occurs along the roadside within the public road right of way. Using this constrained area for stormwater management creates some challenges.
Larger homes being constructed in the neighborhood include much greater percentages of impervious surfaces. The increased size of overall building area generates significantly more stormwater runoff volume collecting along the roadside.
The point of stormwater discharge is the tidally influenced sensitive receiving waters of the Vanderbilt Lagoon. All points of discharge are known and have been inspected. These are existing pipes that run from the roadside, between homes, to the seawall and Vanderbilt Lagoon. These pipes are typically located within drainage easements.
Existing, relatively low street elevations coupled with little elevation differential between stormwater outlet pipes and high tide levels severely limit stormwater management capabilities.
Improvements
New stormwater pipe is being installed in some areas. Some pipe is replacing old metal pipe. Some new pipe is being added and installed in locations to enhance the connectivity of the roadside system.
Roadside swale areas are being retained and reconstructed. All roadside areas which had open swale prior to project commencement will remain roadside swale area. Not all areas along the roadside have a swale. Swale areas are not equitably distributed throughout the neighborhood. This was a pre-project condition that will be carried through the new improvements.
Swale area is a required stormwater best management practice. Swales serve as water quality treatment areas collecting and conveying stormwater runoff prior to discharge into the sensitive receiving water of the Vanderbilt Lagoon. Swales are preserved to retain the stormwater runoff water quality improvement component of the project.
Swale areas located near the outfall pipes leading to Vanderbilt Lagoon may hold water during and following rainfall events. These are typically points or areas of lower elevations for the roadway and the roadside to facilitate runoff collection and conveyance. Swale areas in these locations may also hold water during periods of high tides.
Vanderbilt Drive
Challenges
Stormwater runoff from the Naples Park Area and Vanderbilt Drive collects along the current system of pipes and ditches on the east side of the Vanderbilt Drive right of way. The pre-project condition of the existing system of pipes and ditches was poor and not functioning at an acceptable level of service. Some existing pipes are old and in failing condition. Some areas had no pipes or ditches to convey or collect stormwater runoff. In some areas the roadside ditch and ditch slopes were a hazard to drivers along Vanderbilt Drive. Existing vegetation adjacent to some sections of the roadside ditch is impeding proper collection and conveyance of stormwater along the roadside.
The area along Vanderbilt Drive was also designed and built prior to modern stormwater management regulations and practices. Since there are no existing common areas designated for stormwater management, all collection, conveyance, and treatment of stormwater runoff occurs along the roadside within the public road right of way. Using this constrained area for stormwater management creates some challenges.
Larger homes being constructed in the neighborhood include much greater percentages of impervious surfaces. The increased size of overall building area generates significantly more stormwater runoff volume collecting along the roadside.
The majority of the roadside area along the east side of Vanderbilt Drive up to the right of way line must be cleared of most all objects, trees and vegetation for installation and utilization of new utility and stormwater management infrastructure.
Improvements
Stormwater management improvements along Vanderbilt Drive are primarily limited to the east side of the right of way. The system includes installation of a perforated pipe in a rock filled exfiltration trench adjacent to installation of a new potable water main.
The stormwater management pipe will provide collection, conveyance and exfiltration of stormwater runoff prior to discharge into the sensitive receiving waters of the Vanderbilt Lagoon. The new pipe will replace all existing pipes along the east side of the right of way.
The new pipe will be placed in approximately the same location as the existing roadside ditch. A new shallow swale will be constructed above the new pipe to provide water quality treatment for runoff from Vanderbilt Drive.
All of the old existing stormwater management infrastructure along the east side of the Vanderbilt Drive right of way from 91st Avenue N to 111th avenue N. will be removed and replaced with a new pipe, yard drains and catch basins.