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Feb

22

2024

From The Blog

2024 Drainage Projects Make Proactive Advances and Improve Efficiency

As a barrier island bordered by the Kiawah River and the Atlantic Ocean, efficient drainage is critical. Annually, the community association invests approximately $1 million in an ongoing effort to maintain and repair existing drainage infrastructure. In addition, while we tend to think of drainage as solely pipes and outfalls, there are items in other budget categories that also impact drainage. KICA staff consistently collaborate on optimizing this system and all its parts.

Drainage Optimization

Rhett’s Bluff Pipe Repair

Earlier in February, a KICA contractor completed the slip-lining of several pipes in Rhett’s Bluff. These pipes were identified in KICA’s annual reserve study due to their age and condition. Slip-lining is a process by which older, damaged pipes are repaired by inserting a liner that hardens into a new, seamless pipe inside the old shell. Pipes repaired this way save money for the association and the members, but also allow for a more convenient process. Because the pipes are cleaned out, and the liner inserted inside, large disturbances from digging up and laying new pipe are a thing of the past. The new pipes have an expected life of 30-40 years. 

Tideflex Valves for Backflow Prevention

Tideflex valves will also be added to four of the outfalls in Rhett’s Bluff. These valves are a significant improvement for backflow prevention, especially important for low-lying Rhett’s Bluff (pictured in both images above). 

Previously, the island’s outfall structures were fitted with flap gates. As the name suggests, these structures cap the end of an outflow pipe and include a heavy flap cover that opens when water flows out but closes when water, such as a rising tide, flows back against the gate. (See the gates pictured above, closed against the incoming tide.) Many of these gates are also wheel-driven; those rely on a member of KICA’s Lakes department to manually (in most cases) turn the gear that raises the gate. While flap gates were previously the preferred method of reducing backflow, they do have some issues:

  • They are metal and degrade over time in water, causing them to require additional maintenance. The gates pictured above also have bivalve and barnacle growth from immersion. This can impact function over time.
  • They are prone to sediment intrusion, which can enter the system or affect the operation of the gate.

The association is seeing some of these maintenance issues at Snowy Egret, where the gate has pulled away from the outfall mechanism. This outfall, which drains into the upper section of Cinder Creek, will be repaired in the coming weeks. While this outfall will not be transitioned to a Tideflex valve, it illustrates some of the maintenance that must be performed over the life of a traditional gate.

The Tideflex valves reduce or eliminate these issues, limiting the maintenance that must be done over the life of the valve. KICA’s civil engineer Ryan Ellmers notes that Tideflex valves will be installed in areas that flow directly into tidal marshes, rather than into pond systems, as the habitat of the pond system is enhanced by some controlled tidal inflow. Next on KICA’s list are installations on Burroughs Hall and Airy Hall.

Flood Mitigation Projects

In 2020, KICA members approved a series of six new drainage infrastructure projects. These projects were the first large, new infrastructure added by the community association, which typically receives infrastructure through conveyances. In this case, a task force of members, KICA staff and outside consultants saw a need to combat flooding in this new way. Since 2020, nearly all of the projects have been completed. The engineering for the final phase of the last project, #6 – Trumpet Creeper, is being revised and work is expected to be complete by mid-year.

(Unlike infrastructure repair and replacement projects, which are funded through the reserve budget, the six projects requiring new infrastructure have been funded through the Flood Mitigation Special Assessment.)

Maintenance and Monitoring

While KICA has not yet received the results of its bathymetry survey, the team has identified two ponds (54 and 72) that need to be partially excavated at the pipe outfall to assist with drainage. KICA staff are in the process of getting proposals for the scope of work and will proceed once those are received.

Following storms in December and January, KICA had a contractor on the island to proactively clean out drainage pipes that may have become clogged with debris. This is standard procedure for the association after a storm: areas of concerns are identified by staff and are addressed as soon as possible to avoid stress on the drainage system.

These projects, which will be completed in early 2024, are just a small portion of the work that KICA’s Major Repairs and Replacements Department completes throughout the year. Members whose properties will be directly impacted by the projects will be notified prior to the start. 

For more information about any of these projects, contact KICA’s in-house engineer Ryan Ellmers at [email protected].