Project Spot Light: Charleston, SC Drainage Project- Mar Mac Filter Fabric Skirts
Charleston, SC: Charleston is home to great food, friendly people, and a wealth of history. Unfortunately beneath the densely packed streets of Charleston there lies an often unseen but difficult problem that becomes all too apparent when the pavement is peeled back. Charleston, like much of the South Carolina “Low Country” has a combination of coast line and sandy substrate. This sandy substrate which is the foundation for much of the historic district and downtown is almost exclusively comprised of extremely fine particles of sand, shell, and silt. To make matters more difficult Charleston sits directly on the Atlantic at or nearly at sea level, this results in a high ground water table and makes below ground infrastructure expansion and maintenance that much more frustrating.
One of the major problems engineers in Charleston faced when revamping and improving the flow capacity of their underground storm water detention systems was that often times sinkholes where appearing in pavement and areas surrounding the manhole access points in this system. These sinkholes were a direct result of the super fine substrate surrounding the manholes entering the storm water system at the connection of the storm water pipe to the manholes and therefore destabilizing and leeching the sand and silt supporting the pavement and roads above.
To solve this costly, pressing and frustrating issue engineers from Charleston in conjunction with engineers from one the largest pipe producers in the US approached Mar Mac Construction Products to deliver a permanent and cost effective solution. Taking all the variables, including the high ground water tables into account, Mar Mac delivered and oversaw the initial installation of a large number of “Filter Fabric Skirts” on a large number of manhole to pipe connections in the downtown area.
Mar Mac’s Manhole Skirts function as a silt and soil tight barrier that allows a controlled amount of groundwater to permeate through while preventing any infiltration of substrate materials into the manhole to pipe connection. The Manhole Skirt attaches to the barrel of the pipe to be inserted and covers the entire joint gap surrounding the pipe and manhole connection. Secured to the manhole structure by a tensioning strap, the skirt permanently prevents leeching of subgrade materials which result in sink holes and potholes.
The Mar Mac Manhole Skirts used in Charleston proved successful and greatly reduced the number of sink holes and costly repairs for the city. Furthermore, the installation of the skirts was easily accomplished with little to no time added to the project. If you or your organization encounters fine or sandy soils or if you experience problems with infiltration at the connection of your manhole to pipes, Mar Mac filter fabric skirts offer an economical, permanent solution that can be installed quickly and will greatly extend the life of your roads and storm water systems.