Thursday, November 20, 2014

T. Tyler Potterfield Memorial Bridge Project

The city has been working with the state to clear woody vegetation near the Brown’s Island Dam. This work needs to be done before work begins on the T. Tyler Potterfield Memorial Bridge (TTPMB). In order to get to the dam, the contractor will need to prepare an access road.

Work began Nov. 18. In order to get to the dam, and to construct the access road, a fair amount of clearance was required. This clearance would have occurred anyway for the TTPMB. 

This is good news for those who have waited so long for the TTMPB to start…and shows real progress on the implementation of the Riverfront Plan.

•Brown’s Island Dam (BID) is regulated by the Dept. of Conservation and Resources, State of Virginia as a Low Hazard (Special Criteria) dam and therefore all woody vegetation within 25 feet of the structure is to be removed. Reference: Impounding Structures Regulations, 4VAC 50-20-10 et seq., including 4VAC 50-20-105, Virginia Soil and Water Conservation Board.

•The dam inspection report by DPU’s consultants Dewberry Consultants, LLC, 12/27/13 recommends the removal of woody vegetation and debris in the south section of the dam and along various piers.

•Requests for removal schedules by PDR were followed by DPU’s request to investigate the possible plan through DPU’s annual contracts.

•A draft drawing shows a tree removal plan that will benefit both the TTPMB project and meet the Low Head Dam requirements. It included a construction entrance that can be used by the successful BIDW contractor from day one to access the lower Southside site. It also includes the erosion and sediment controls required for the small amount of earth (460 square feet) that will be disturbed at the construction entrance. All trees are proposed to be chipped to the ground with no land disturbed. A safety fence adjacent to N-S tracks is shown as a precaution/boundary. DPU and PDR reviewed this plan.

•PDR worked with the TTPMB consultants, Hargreaves Associates, to approve the proposed tree removal routes and actions by G L Howard with comments that would require removal of the wood chips from the sites for future construction access. This would increase the cost and an agreement to spread the chips with future removal was reached.

•Work will begin with all permits in hand after November 18, 2014 and weather-permitting be finished by the end of the month. Work on the TTPMB will begin in earnest by the end of the year.

The Brown's Island Dam that the Potterfield Memorial Bridge crosses is classified as a low hazard dam by the State of Virginia. The state dam safety office thus requires the City of Richmond, the owner of the structure, to maintain a 25-foot clear zone free from woody vegetation around the dam. Clearing this vegetation is a state-mandated part of dam maintenance and Department of Public Utilities contractors will be completing it to fulfill State of Virginia dam safety requirements over the next month.

This required maintenance activity will also help support the construction of the T. Tyler Potterfield Memorial Bridge and paths. DPU contractors will be clearing the same pathway that the Potterfield Memorial Bridge will take in order to access the Brown's Island Dam and move machinery for the dam maintenance activity while limiting impact on the area. The clearing of vegetation in this area will help prepare the area where the elevated pathway for the Potterfield Memorial Bridge will be constructed over the next year. 

The Potterfield Memorial Bridge project has several important sustainability features, including: avoiding all impact to designated wetlands and the floodway, capturing run-off on site in bioswales, and improving water quality of run-off. Over 1,000 native ferns, shrubs, and trees will be planted as part of the project.

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