Charleston has been looking for solutions to flooding on the peninsula for several hundred years, and following Wednesday’s deluge that left some streets underwater, people might ask: How’s that working out?

The Post and Courier asked Laura Cabiness, the city’s Department of Public Service director. She said several long-awaited projects aimed at addressing some of the peninsula’s most vexing drainage problems should be completed by 2020. Here are some of our questions and her answers.

Q: In 1837, the mayor of Charleston offered a $100 gold piece to whoever could suggest the best plan for solving the city’s persistent drainage problems. Did anyone claim that reward?

Cabiness: “No. There are things that can be done to solve the drainage, but the city was developed on low, flat land, and much of it was filled-in creek beds. We have to employ mechanical means — tunnels and pumps — and that’s very expensive.”

Those tunnels can be 140 feet underground and 12 feet wide. The city currently has one pump station on Concord Street, near the Maritime Center, that drains the area around East Bay and Calhoun streets.

Q: Construction on a more than $20 million project to address Market Street flooding began in 2007, but Market Street has been underwater several times this month. What’s the status of that project?

Cabiness: “Actually, the second phase is under construction right now. We finished the first phase in 2008, and spent almost $1.5 million to upgrade the pump station at Concord Street. Last year we awarded the contract for the second phase, which is the deep tunnel.

They are down there digging right now. The shaft is 140 feet down in the ground, and we are boring toward the Concord Street station.

“Eventually, the tunneling work will be followed by surface work to direct the storm water to those tunnels. This phase and the next phase is about $25 million, just for that area.”

Q: During one storm in December 2009, flooding was so bad that the city shut down all roads leading to the peninsula. Does the city have a standing plan to close roads and direct traffic when there is bad flooding?

Cabiness: “We monitor it from our emergency center, and when it gets so bad that cars are flooding out, we do work together and shut those roads down. We try to minimize the impact.”

Q: In the scheme of things — knowing that this happens here — how bad was the flooding Wednesday?

Cabiness: “We did get a significant amount of rain, and it hit right at high tide. So all the old creek beds were affected. As the peninsula was developed, creek beds were filled, and they are still the lowest parts of the city. The peninsula itself is about 50 percent fill.”

Q: The city has a tax dedicated to fixing drainage problems. How much does it raise and where has the money been going recently?

Cabiness: “It’s about $5.5 million a year, and it’s a combination of the storm-water fee and a (property) tax assessment for drainage.

Most recently, we’re using that money to support a bond issue for (drainage projects addressing) Market Street, Forest Acres (in West Ashley), and the west end of Calhoun Street.”

Q: The Septima Clark Parkway (Crosstown Expressway) is well known for flooding and is a focus of the city’s largest drainage improvement project ever. What’s the status of that work?

Cabiness: “The first phase was recently completed, at about $12 million. We were able to make all the surface improvements along Septima Clark Parkway. The next phase, about $20 million, will be more of the same. It’s a large (drainage) basin, almost 500 acres. The third phase will be a deep tunnel, 12 feet in diameter, and ultimately we’ll be building a pump station by the Ashley River.”

A drainage basin is an area where all the water flows to the same low spots. The Septima Clark Parkway project is in the Spring/Fishburne drainage basin, which covers about 20 percent of the peninsula.

Q: How much will that whole project cost?

Cabiness: “The estimate is still $154 million.”

Cabiness said a $10 million federal grant and more than $100 million in state highway and Infrastructure Bank funds will cover most of the cost.

“We’re trying to fix something that’s been inadequate since the day it was built. We anticipate completing everything by 2020, and there’s a possibility it could go faster.”

Q: When will the Calhoun West project be addressed?

Cabiness: “We’ll begin engineering this year. Typically, a project this size takes two to three years.”

Calhoun West is the drainage basin surrounding Calhoun Street and Rutledge Avenue, including MUSC and parts of Harleston Village.

Q: The sea level is rising, and that rise is expected to accelerate due to climate change.

Has an impact been seen in city flooding, and how big a concern is the changing sea level?

Cabiness: “I think it has been seen. If you look at the NOAA website, they document that the tide in Charleston has been rising a little over a foot every 100 years.There’s debate about how fast the sea level will rise, but there will be an impact. Storms have also been getting more intense, with more rain in less time.”

Q: When all the pump stations and tunnels are built, will there still be flooding?

Cabiness: “We’re not building pump stations to protect the city from a hurricane surge, but we’re building them to try to deal with the stuff we had yesterday, and to keep evacuation routes clear.”

Reach David Slade at 937-5552 or Twitter @DSladeNews.