Cardinal Engineering Associates - 55 years of excellence

Cardinal Engineering was retained by the Town of Hamden to conduct a drainage study in the Beaver Street Area of Hamden. The study analyzed the drainage area contributing to the flood-prone Beaver Street, the condition and the hydraulic capacity of the existing closed drainage system. The study highlighted the existing problems and proposed solutions to alleviate the flooding in the area.

Cardinal Engineering determined that stormwater runoff from the area between Woodin Street and Second Street floods the road frequently. During moderate–to heavy rainfall, the water level rises quickly in Beaver Street to depths of 8–10 inches and adversely impacts several properties located in the lower area of the street.

To remedy the situation, Cardinal studied the existing drainage systems on Woodin Street, Fourth, Third, Second and Beaver Street down to the 8'x4' culvert on Fairview Avenue; conceptual drainage improvements are proposed on Beaver Street, between Second Street and Woodin Street.

The hydrologic analysis utilized the Rational Method to compute the existing flows to the Beaver Street drainage system and the contributing drainage systems.The hydraulic analysis of the drainage systems was performed with the Hydraflow computer program. All hydrologic and hydraulic calculations and designs conform to the Connecticut Department of Transportation Drainage Manual 2000, with latest revisions.

The results of the hydraulic analysis show a 10-year design flow of 29cfs to the closed system on Beaver Street; the existing system capacity is approximately 8cfs. A capacity upgrade of the closed drainage system will be necessary.

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Proposed Improvements

Proposed improvements at the Beaver Street drainage system consist of replacing 1,100ft of existing 15" pipe with a new system capable of conveying the 10-year flows. The proposed system was checked for the 25-year flow, according to the ConnDOT recommendations for sag condition. The new system will consist of 600ft of 30" RCP from the junction with the Fairview Avenue culvert up to the Third Avenue intersection; 250ft of 24" pipe up to the Fourth Avenue junction, and 250ft of 18" pipe up to the intersection with Woodin Street.

The existing catch basins will be replaced with new type "C" catch basins. At the low point, new double grate type II catch basins should be installed. Flanker catch basins on both side of the road would provide additional capacity during intense rainfall events carrying debris in the low area. At the north end of Beaver Street, double grate type I catch basins will collect overland runoff from the areas north of Woodin Street.

The need for additional catch basins or upgrade of the closed drainage systems in Third and Fourth Street will be determined in the next phase of the project. A preliminary construction cost estimate using the ConnDOT Preliminary Cost Estimating Guidelines and unit prices from recent bids shows a total cost of the proposed drainage improvements of $498,000.

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