Dec 09, 2013Outdated storm-sewer maps get an upgrade
CHARLESTON, W.Va. Engineers are taking the next step in Charleston's storm watersewer system mapping project, connecting plotted manholes and inlets on the city's surface with the system of pipes that run beneath.
The city's stormsewer system hasn't been thoroughly mapped since the 1930s or updated since the 1970s, according to Tom Elkins, the city's stormwater manager. The city often finds this information is outdated, as maps don't include improvements or projectspecific drawings exist only in individual files and on paper.
"Things do exist, but is it exact? No," Elkins said. "It became a picture in time until now."
This mapping wasn't a requirement until the Clean Water Act made it so in 2003, Elkins said.
"What we have is no longer accurate," said project manager Scott Howell, He works for Michael Baker Jr. Inc., a consulting firm contracted to process that information and develop a database using GIS technology.
Charleston subcontractor E.L. Robinson Engineering has been recording the characteristics of the subsurface system for the past six months, according to Howell. This information will be placed in a GIS database a computerized mapping information system that stores information.
"As we speak, the guys are out in the field right now ... popping the lids on these manholes and lifting the grates from these inlets, measuring, taking photographs, finding out size, condition and flow direction of pipes," Elkins said.
This mapping (a requirement of the Environmental Protect Agency and the Clean Water Act) began in 2011 to create an inventory for the city to use when dealing with variety of topics, such as storm water or sewerage system repairs and projects, construction and development.
Connecting the components of the city's stormsewer system will help the city make better decisions more efficiently when it comes to changing or repairing the system, Elkins said.
As it stands now, the city is unable to simply look up a specific inlet an opening where water flows into the sewers or pipe and share information about it, whether it is with a repair crew or a business entity looking to locate in Charleston.
"We can't tell you what's out there," Elkins said. "We have to do a field investigation. Sometimes that takes weeks or longer."
Not having uptodate information makes it challenging to determine what amount of drainage or overflow they can handle or what might be needed to alleviate overflow in areas prone to flooding. Having the information in a database will also make it easy to share information across departments and better determine the cost of projects, Elkins said.
"We want to know what we can do and what it'll cost," Elkins said of determining the price of solutions.
The city is working toward the goal of better controlling the effect storm water run off and precipitation from rain has on the city. About 80 percent of Charleston's stormsewer system is combined.
It was designed to overflow during rainy storms in order to flush systems into the Kanawha and Elk rivers, Elkins said. The lines continue to overflow to this day.
"There's no way around that," Elkins said.
This design proves to be problematic in terms of water quality and quantity, Elkins said. There are 59 Combined Sewer Overflow points in the city. If there is 1/4 inch of rainfall, Elkins said, pipes in these areas reach their capacity and overflow into the river or flood neighborhoods.
"You end up with diluted, ... raw sanitary sewerage into the streams," Elkins said.
Those 59 CSO points are legal, but they are only permitted to release so much sewerage into streams each day their Total Maximum Daily Load, or TMDL. But, that's not meant to last forever, and analysis based on new maps will help, Elkins said.
The overall goal is to eliminate CSO and reduce risk for flooding and pollution.
"By mapping the entire system, we know where we can alleviate maybe put in a separate storm sewer or remove water from the sewer system that will affect that CSO to the point where it won't have as many overflows," Elkins said. "We're kind of killing two birds with one stone here with all this mapping."