CDM News - August 2007 - (Page 6)

Preserving Old Town Alexandria The city of Alexandria, Virginia, is located on the west bank of the Potomac River, about 7 miles from Washington, D.C. Founded in 1749 as a seaport serving area plantations, it is one of America’s most historic communities and includes the neighborhood of Old Town Alexandria—a historic district that has retained its colonial charm and remains today a popular tourist destination with restaurants, specialty shops, art galleries, and many cultural activities. Additionally, this urban, historic neighborhood is a residential hub, with two-lane traffic, on-street parking lanes, and twoto three-story buildings on both sides of the street. The city owns and operates an extensive underground infrastructure system, which includes the Tanyard Ditch, a combined sewer system located in Old Town Alexandria. During the past 10 years, downstream surcharging in Tanyard Ditch has resulted in repeated street and home flooding at the intersection of Pitt and Gibbon streets. Flooding has been reported in back yards, on the ground floor of residences, and in the street. On occasion, floodwaters, which include combined stormwater and sewage, have been reported to be an estimated 1.5 feet deep. “We had homes that experienced flooding repeatedly over the years during intense rain events,” explained Emily A. Baker, P.E., city engineer and member of the city’s Department of Transportation & Environmental Services. “For homes below street level, this was a real challenge, and cars were often damaged as well. The flooding affected the quality of life for residents.” Pitt and Gibbon streets. Consequently, the city initiated a capital improvement project involving the construction of a new storm sewer and outfall improvements to address the flooding. During the preliminary design phase, various alternative alignments for the new storm sewer were created and evaluated based upon a review of existing surface conditions, potential utility conflicts, hydraulic capacity, public disruption and traffic control requirements, easement acquisition requirements, geotechnical investigations, and constructability issues. The selected storm sewer alignment required construction across a topo- CDM performed a flooding evaluation study to assess the conditions and causes and to identify and evaluate alternatives to address those problems. Results of preliminary engineering analyses and studies concluded that surcharging within Tanyard Ditch prevented stormwater runoff from entering the combined sewer system at the intersection of Mitigating Community Disruption

Table of Contents Feed for the Digital Edition of CDM News - August 2007

Contents Envisioning Tomorrow’s Dublin Initiative & Innovation Stabilize Mercury Mines Preserving Old Town Alexandria Taking a Hard Look at Concrete Corrosion Perspective: Harnessing Bioenergy Engineering Better Lives CDM Announces Award-Winning Projects People Highlights

CDM News - August 2007

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