National Capital Planning Commission1 File: 8042January 9, 2020 | File: 8042

United States Department of Defense

Approval of Final Site and Building Plans

2500 1st Street, NW, Washington, DC

McMillan Reservoir Backwash Equalization Pumping Station

National Capital Planning Commission2 File: 8042

Project Summary:NCPC File Number:

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Project Summary

The United States Department of Defense, Army Corps of Engineers (USACE) has submitted final site and building plans for the new Backwash Equalization Pumping Station at the McMillan Park Reservoir. The project is located in the eastern portion of the McMillan Park Reservoir Historic District, between the existing Filter Building and McMillan Drive, NW. The purpose of the project is to provide Washington Aqueduct (WA) with a supplementary method for disposing filter backwash water from the daily cleaning of filters used in drinking water treatment. The proposed action would allow Washington Aqueduct to more efficiently and safely accomplish its mission of providing high quality drinking water in sufficient quantities while meeting regulatory requirements.

Currently, the filter backwash water is discharged into a cove area of the McMillan Reservoir, where solids in the filter backwash water settle out of solution. The water returns to the main body of the reservoir and is recycled through the water treatment plant. The project will allow the WA to discharge most of the filter backwash water to a combined (sanitary and storm) sewer system operated by DC Water during dry weather conditions, for treatment at the Blue Plains Wastewater Treatment Plant. During wet weather conditions, the filter backwash water will continue to be recycled through the McMillan Reservoir. The project will reduce the volume of solids discharged to the McMillan Reservoir by approximately 90 percent.

8042

Lee Webb

Delegated

Approval of Final Site and Building Plans

40 U.S.C. § 8722(b)(1) and (d)

January 9, 2020

National Capital Planning Commission3 File: 8042

Project Summary

The scope of the project includes construction of a new pumping station and underground treatment basin with associated site improvements, such as minor grading and pavement restoration. The total project construction area is approximately 14,000 square feet, including:

• A 3,340 square-foot pumping station. The two-story building will house a flow meter and control valve room, electrical room, and monorail room.

• A 660,000-gallon backwash equalization basin, approximately 7,500 square feet. The basin will be located below grade.

The proposed exterior finishes will match the existing Filter Building. The materials include brick, white aluminum windows and doors, horizontal banding and stone coping. Construction is scheduled to be completed by the end of May 2021.

Six existing pine trees and one existing flowering tree will be removed to construct the proposed facilities. Two American Holly and seven Yoshino Cherry trees will be planted near the proposed basin to offset this removal.

The preliminary application for the project was reviewed and approved in March 2019.

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Location Map

Site Location

Location Map

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Site Plan

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Enlarged Site Plan

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Surrounding Plant Buildings

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Floorplans

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Roof Plan

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Sections

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Sections

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Elevations

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Sections

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View from 1st Street NW Looking West

Existing Proposed

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View from Inside Plant Entrance Near 1st Street Looking West

Existing Proposed

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Isometric