Virginia Coastal Program: 2007 Coastal Grant Project Description and Final Summary
Project Task:
5
Grantee:
Virginia Department of Environmental Quality - Chesapeake Bay Program
Project Title:
Water Quality Improvement Fund Match
Project Description as Proposed:
Water quality improvement is a key aspect of Virginia’s CZM Program. Two of our 9 enforceable policies deal with water quality – point and nonpoint source pollution controls. Goal #2 of our Executive Order directs us to “restore and maintain the quality of all coastal waters.” For the past several years, recognizing those goals, Virginia’s General Assembly has set aside millions of dollars in state funds to upgrade sewage treatment plants with biological nutrient removal systems. These systems have proven extremely effective in reducing nitrogen outputs by about 65%.
In FY 2005-2007 matching funds for Virginia’s CZM awards are being provided in part through DEQ’s Water Quality Improvement Fund grants (WQIF Grant: #440-S-07-10) to Arlington County for their multi-million dollar sewage treatment plant upgrades. Work planned for FY 2007 will include elements (to be determined) from Design Package (CP #2) No.2. See “Extended Project Summary” for details of Design Package No. 2.
DP-2 will expand the biological treatment capacity of the ACWPCP from 30 MGD up to 40 MGD and provide for future reduced levels of effluent total nitrogen less than 8 mg/L. It will include the following major elements:
• Demolition of existing lime handling facilities (to provide room for construction of aeration tanks and secondary clarifiers);
• Construction of 1 or 2 new aeration tanks and blower replacements;
• Mixed liquor flow distribution improvements;
• Existing secondary clarifier renovation;
• Construction of 2 or 3 new secondary clarifiers and related pump station;
• Activated sludge effluent pumping system improvements;
• Waste backwash system modifications;
• Security and aesthetic improvements; and
• Supervisory Control and Data Acquisition (SCADA) system.
The ACWPCP currently has facilities that were originally provided to allow lime-clarification to be used for phosphorus removal. These facilities have been modified and are currently used to provide tertiary clarification upstream of the effluent filters (using ferric chloride as a coagulant). As indicated above the structural condition of the Lime Reaction Tanks (LRTs) is very poor and the tanks will need to be demolished. The demolition of the LRTs will facilitate the construction of the new aeration tanks and secondary clarifiers. The following facilities will be demolished:
• Three First Stage LRTs each 120 feet square;
• Three Second Stage LRTs each 120 feet square;
• One multi-story masonry Lime Solids Processing Building which has been modified to provide storage and feed equipment related to the ferric chloride system; and
• Two Lime Sludge Thickeners each approximately 60 feet in diameter that are no longer used.
The ACWPCP currently utilizes four aeration tanks to provide BOD removal and Biological Nutrient Removal (BNR). The tanks are configured to operate in the step feed BNR mode. Each tank has four separate passes. The new aeration tank(s) will be constructed for BNR, redundancy and reliability, and increased capacity. The new aeration tank(s) will be four-pass, step feed biological treatment reactors, similar in arrangement to the existing tanks.
The mixed liquor flow distribution system will be upgraded to provide improved effluent quality and extended to serve the new aeration tanks. Two new flow distribution structures will be provided at each end of the new mixed liquor channel to provide even flow distribution to all of the existing and new clarifiers. At this time it is not clear whether the upgrade and expansion at ACWPCP will require 1 or 2 new aeration tanks. Studies are ongoing to determine the quantity of aeration tanks required to effectively improve treatment capabilities, increase redundancy and reliability, and meet projected flow requirements.
DP-2 will provide two or three new circular secondary clarifiers. Each unit will be 140 feet in diameter, with a sidewater depth of 16 feet. In conjunction with the ongoing studies described above to determine the number the new aeration tanks, the number of new secondary clarifiers is also being evaluated. In addition to the new clarifiers, the six existing clarifiers will be modified as needed to replace old mechanisms and improve sludge withdrawal and scum removal.
A new ASE pump station will be provided with the new clarifiers.
Federal Funding:
Match to Virginia CZM Program grant from NOAA Only - $698,036.00
Project Contact:
Robert W. Ehrhart, 804.698.4466; Robert.Ehrhart@deq.virginia.gov
Project Status:
10/1/2007 - 9/30/2008: Project Completed
Final Product Received:
Project Summary Provided by Grantee:
The web address for this project is: http://deq.virginia.gov/bay/wqif/arlington.html . At the completion of the construction project which spans multiple years, the total nitrogen delivered to coastal waters at design flow will be reduced by 609,112 pounds per year. Work to date and/or since the previous report has included:
• Completed installation of steel foundation piles at the West Secondary Services Pump Station (WSSPS), Aeration Tanks #5 and #6 and the West Mixed Liquor Distribution Structure. All 7B Milestone 1 steel foundation piles have been installed.
• Continued form and rebar installation and concrete placement for walls, baffle walls, elevated channels at Aeration Tanks 5 and Mixed Liquor Channel
• Completed placement of foundation and base slab concrete at Secondary Clarifier #7.
• Completed concrete wall placements at Secondary Clarifier #8.
• Continued installation of forms, rebar and concrete for Primary Clarifier #7 and #8 modifications.
• Performed electrical rough-in at the South Tunnel Access Building, Secondary Blower Building including the Electrical Room addition, Aeration Tanks #5 and #6, Primary Clarifiers, Preliminary Treatment Building (PTB), PTB Back-up Structure, and West Secondary Services Pump Station.
• Installed direct buried electrical conduits at the Primary Clarifiers.
• Installed yard electrical rough-in for site lighting at the Dissolved Air Flotation Thickener (DAFT) and Maintenance Buildings and the Potomac Interceptor head works.
• Commenced excavation and utility relocation at the Surface Waste Pump Station (SWPS). Installed buried utility piping north of SWPS as well.
• Installed and tested buried and embedded piping serving Secondary Clarifiers #7 and #8 and the West Secondary Services Pump Station.
Payments and/or work associated with the FY 2007 grant relate primarily to the new secondary clarifier structures
Construction of the Contract 7b nutrient reduction project will be completed in two parts: Part 1 -3/30/2010 and
Part 2 – 7/31/2011. Contract time elapsed to date is about 40%. Based on contractor payments the project is 38% complete; however, 100% of the match has been paid.
Disclaimer: This project summary provides the federal dollars initially awarded to the grantee. Due to underexpenditure or reprogramming of grant funds, this figure may change. For more information on the allocation of coastal grant funds, please contact Laura McKay, Virginia Coastal Program Manager, at 804.698.4323 or email: Laura.McKay@deq.virginia.gov
A more detailed Scope of Work for this project is available. Please direct your request for a copy to Virginia.Witmer@deq.virginia.gov