Technical Advisory Working Group Meeting
April 15, 2004
Review of Desktop Analysis, Consideration of Independent Peer Review Panel Recommendations
and Consensus on Treatment Option
This meeting was convened with the goal of the Technical Expert Working Group (TEWG) reaching consensus on the type of revised corrosion control treatment to pursue, the timeline in which it is to be done and the procedures with which to monitor its successfulness.
CH2M Hill and the Washington Aqueduct provided a summary of the Desktop Analysis, including the newly added Section 6. This new section documents the Independent Peer Review Panel's recommendations and the Aqueduct's proposed responses to the major recommendations. The responses included concurrence with the Independent Peer Review Panel's recommendation to use zinc orthophosphate (ZnOP) instead of phosphoric acid (orthophosphate), as the corrosion inhibitor. Other Independent Peer Review Panel recommendations that the Washington Aqueduct proposed to accept were: the target dose of ZnOP is to reach a residual of 3 mg/L in the distribution system as sampled from taps; starting at this high dose rather than ramping up to it; and operating at a pH target of 7.7 ± 0.3 in the distribution system. The Aqueduct and its consultants will implement improvements to the existing lime feed system (pH control process) to optimize the ability to maintain steady pH and, after the ZnOP treatment process design and construction are completed, they will study means of optimizing pH to 7.7 ± 0.1 and install any necessary treatment equipment as soon as possible.
Zinc can be a limiting factor in wastewater discharge permits and in biosolids disposal. The recommendation is to use this inhibitor at a weak 1:10 zinc to orthophosphate ratio. This lower concentration of zinc is not expected to cause any problems for wastewater discharge. Additional investigation needs to be quickly conducted to determine if zinc orthophosphate will cause any problems in wastewater treatment and residuals handling due to the zinc component. EPA, through a contractor, will be conducting an overall review of both Blue Plains and Virginia wastewater utilities’ ability to handle the ZnOP without causing any Clean Water Act or Resource Conservation and Recovery Act compliance issues.
The TEWG agreed to the proposed modifications to the Desktop Analysis. This includes the recommendation to move up the full system application of ZnOP to on or about July 15, 2004 if the partial system application in the 4 th high pressure zone has no major problems. The TEWG expressed its concern over starting the full system application of ZnOP before the majority of the District's distribution system was flushed. To prepare for this, additional attention will be paid to similar areas in the partial system application area. The D.C. Water and Sewer Authority (DCWASA) believes that it will have flushed 80% of the 4 th high pressure zone prior to the partial system application. DCWASA and the Washington Aqueduct will closely monitor the un-flushed portions of the 4 th high pressure zone for evidence of red water problems. These sections of water main may serve as a model for the rest of the District's distribution system that will also not benefit from flushing prior to ZnOP treatment due to moving up the full system application start date to mid-July. A decision point was set for the 6 th week of the partial system application at which point the TEWG will decide on moving forward with the full system application.
The Working Group also expressed concern over maintaining the most constant pH possible in the distribution system. EPA suggested that a pH trigger be built into the operating parameters that would, in the event of a severe pH fluctuation, call for additional action by DCWASA, such as spot-flushing, to bring pH to the target of 7.7.
DCWASA presented its proposed monitoring plan to be used during the partial system application. The Working Group members provided comments and a revised version will be distributed for final review.
EPA's corrosion expert, Mike Schock, Office of Research and Development in Cincinnati, OH, presented a summary of his findings from analyses of lead service line internal pipe scale (mineral coating). His analysis indicates that the scale is predominantly made up of lead IV mineral whereas the majority of lead service line pipe samples he has analyzed from other cities are predominantly lead II mineral. Since the ZnOP treatment will interact with pipe scale different from any others he has experienced, Mr. Schock cautioned that other cities' experiences with this corrosion inhibitor may not be transferable to the District, particularly with regards to the amount of time it will take to reduce lead levels at the tap. There is no data or information available to use as a reference on how long this might take. Mr. Schock also cautioned that the District might even see temporary increases in tap water lead levels as the lead IV mineral transforms to the lead II mineral. This particular detail of lead mineral chemistry has not been researched, thus the mechanism for this process and any resulting short-term changes (increases) in lead levels is not known.
The Working Group agreed to add a section to the TEWG's Action Plan to address health precautions, particularly with regard to red water that could develop for a short time after application of the corrosion inhibitor.
Various members of the TEWG briefed the group on the current status of research being conducted under the Action Plan. Preliminary results from the electrochemical pipe loop studies are being reviewed by EPA's contractor. The Aqueduct now has enough lead service line pipe to complete construction of their larger-scale, flow-through pipe loops. The Communications Team of the Working Group outlined the plans for holding two public availability sessions on the proposed treatment revision. These sessions are to be scheduled near the end of April and will also include general public education on the research and other work being conducted under the Working Group's Action Plan.
The Working Group's consensus allowed the Washington Aqueduct to submit a formal, revised optimal corrosion control treatment proposal request to EPA at the end of the day. EPA's goal is to review this proposal and reach a decision on or about May 1, 2004.
EPA: Rick Rogers (Region III), Eric Burneson, Jeff Kempic, Patricia Moe (Headquarters), Mike Schock (ORD Cincinnati). EPA Consultants: Laura DuFresne (Cadmus), Steven Reiber (HDR) via telephone
Centers for Disease Control and Prevention: Barry Brooks
D.C. Department of Health: James Collier
Washington Aqueduct: Tom Jacobus, Patty Gamby, Lloyd Stowe, Elizabeth Turner, Miranda Brown, Dan Shaw, Jim Bemis. Aqueduct consultants: Phil Hecht and Glenn Palen, CH2M Hill and Vern Snoeyink, University of Illinois
D.C. Water and Sewer Authority: Rich Giani. DCWASA consultants: James Poirier and John Civardi, Baker Killam Joint Venture, Marina Moses, George Washington University
City of Falls Church: Bob Etris. Falls Church consultant: Anne Spiesman, CDM
Arlington County: Dave Hundelt