Mapping the city’s drainage

Published 12:00 am Friday, August 3, 2007

FRANKLIN—Among the more than 4,100 elements of the city’s storm water system are approximately 794 curb drain inlets, 592 catch basins, 243 flared end sections and headwalls, 250 manholes, 2,200 pipe ends—and one frog.

Engineer David Reaves of Prism Engineering and Contracting of Yorktown recently noted the number of elements he had identified as he updated the City Council on the progress of the city’s comprehensive storm water study.

&uot;It will be around the middle of next year before (the project) will be complete,&uot; he said.

Reaves is waiting on aerial photographs taken by the state.

&uot;(The area) didn’t get flown until this winter,&uot; he said, &uot;and they flew the whole state.&uot;

Virginia Geographic Information Network is a state agency that offers this service much more cheaply than it would cost to hire a pilot.

According to Deputy Director of Public Works Chad Edwards, for the cut in costs, the department is not complaining about the length of time it takes to get the photos.

&uot;The aerials will provide us with contour lines that will show a detailed layout of the land,&uot; he said. &uot;They can only fly in the winter (to get these photos) when there is no foliage on the trees.&uot;

He said having a map of the city’s elevations will provide information that will enable the department to evaluate the system during storms.

In addition to the digital topography, the project, once complete, will include Reaves’ work on the identification and surveying of critical storm drain components, the generation of a database and map of the critical components, and the creation of a storm water model.

The digital map will enable the department to feed in information and find out where problem areas may lie.

Edwards said, &uot;We could have five inches of rain in two hours, put that in the model, and it can tell us where the system will flood and what it will affect. Plus, (Reaves) is inspecting storm water structures and pipes, which will let us know where our deficiencies are.&uot;

Edwards said the approximately $150,000 project began in 2006.

&uot;The main reason for doing this is because the city has no overall mapping,&uot; he said. &uot;We have bits and pieces, and site-specific areas when they were built.

&uot;This will give us a comprehensive map of the entire city that will show us, for example, where our storm water pipes are and how the water is conveyed.

&uot;We’re just waiting on the state for that data, which will be the base mapping for the whole system.

&uot;Without having this system modeled, it’s hard to know what you’ve got and whether it is adequate.&uot;