Has Washington Aqueduct made a final decision on the alternative treatment for its water treatment residuals?
Yes. Washington Aqueduct selected Alternative E as the preferred residuals management process for reasons of environmental impact, scheduling of implementation, and cost. The preferred alternative treatment involves collecting residuals from both the Dalecarlia WTP sedimentation basins and the Georgetown Reservoir and processing the residuals through gravity thickening and dewatering as well as trucking them to a disposal facility off site.
How many alternatives were considered?
160 residuals management alternatives were considered.
How many alternatives were evaluated?
Five (A- E) alternatives were carried to the EIS for detailed evaluation.
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A
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Dalecarlia- adjacent to maintenance buildings
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Monofill
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Would not comply with Federal Facility Compliance Agreement (FFCA) schedule. Would have long term adverse impacts on various natural and community resources. Schedule conflict with remediation efforts at
American University Experimental Station.
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B
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Dalecarlia – adjacent to maintenance buildings
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Trucking
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Would meet the conditions of the permit No. DC 0000019 within the (FFCA) schedule.
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C
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Thickening at Dalecarlia and dewatering at Blue Plains
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Pipe to Blue Plains
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Would not comply with (FFCA) schedule. Would have adverse impacts on various natural and community resources. Cost was doubled the other alternatives.
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D
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No Action
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No Action
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Would violate Clean Water Act.
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E
(Recommended)
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Dalecarlia – adjacent to Sibley Hospital
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Trucking
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Would meet the conditions of the permit No. DC 0000019 within the (FFCA) schedule. Less visual impact, less truck noise and fewer oil issues
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What does the project consist of?
- Installation of new collection equipment to the sedimentation basins at Dalecarlia Water Treatment Plant and the Georgetown reservoir. This allows the residuals to be collected on site.
- Construction of dredge system and pumping stations at the Forebay, Dalecarlia sedimentation basins and Georgetown reservoir. The pumping stations will allow collected residuals to be pumped to the residuals processing facility.
- Construction of four gravity thickener basins. The thickener basins are located near the residual processing facility. This will provide temporary storage of liquid residuals pumped from Georgetown Reservoir, Forebay and Dalecarlia Residuals pumping stations and to thicken the residuals prior to dewatering.
- Construction of a central residuals processing facility. The residuals processing building will allow residuals to be collected and conveyed from the Forebay portion of the Dalecarlia Reservoir and the sedimentation basins at both the Georgetown Reservoir and the Dalecarlia WTP to the central location to be thickened and dewatered prior to being loaded onto trucks that will haul the residuals to a disposal site.
How will the residuals be disposed of?
The residuals will be dewatered and hauled away by trucks to a site undetermined at this time.
How many truck loads are expected?
An estimated maximum of normally eight truck loads per day (5 days per week) of dewatered residuals are expected to be transported from the Dalecarlia WTP site on average.
What is the truck travel schedule for hauling away the residuals?
The truck trips will occur during weekdays between 9:30 a.m. and 4:00 p.m.
Who is responsible for trucking the residuals?
Washington Aqueduct will use a contractor to truck the residuals.
What steps will be taken to mitigate neighborhood noise?
- Will use concrete masonry building materials to absorb sound.
- Will use closed truck bays to control residuals loading and truck start-up.
- Will not permit construction on Sundays or holiday from 7:00 pm to 7:00 am.
Will there be landscaping?
- Yes. There will be extensive landscape plantings installed around the Residuals Processing facility and a new earthen berm, with a height ranging from 6 to 8 feet. Soil excavated during the construction of the facility will also be mounded up against the gravity thickeners associated with the Residuals Processing building to lower visible height.