Field Office Compliance - Assistance

Assistance ID - 48981
Des Moines Water Works - 310338211
9966 Maffitt Lake Dr Cumming, IA 50061
Dallas County

FO 5

Report
File Name File Type File Date Note
Comments
6/12/2012 From: Gastineau, Janet [DNR] Sent: Tuesday, June 12, 2012 10:45 AM To: 'McCurnin, Mike' Subject: RE: Altoona Connection from Southeast Polk South PWS Do we have the most recent number of connections for the SE Polk south system? Monitoring for chlorine residual at the source/entry point to the Altoona and SE Polk South systems followed by HPC monitoring for up to 90 days is acceptable as you describe below. I would also like to see additional monitoring for chlorine residuals and follow up HPC monitoring performed in the applicable distribution system(s) to determine how the potentially low chlorine levels are affecting the DS. Please work with Altoona to identify where water from the joint east side tower flows to identify a representative DS location(s) for monitoring. Your staff can make decisions on where in the SE Polk South and Pleasant Hill/DMWW distribution systems to monitor. The HPC monitoring should be considered routine (not specials) when they are being measured in lieu of a detectable residual disinfectant concentrations and should be included in the respective system’s value “V” calculation. If HPCs are run when there is detectable residual but less than 0.3 mg/L, for example, they can be considered specials. You are also reminded that all results of drinking water analyses performed by certified environmental laboratories must be submitted to the department, or its designee such as SHL, using forms provided or approved by the department or by electronic means. [567 IAC 83.6(6)”a”] An implementation scheduled for improvements based on conclusions from the data gathered would be expected to be prepared by September 15, 2012. Thank you for the opportunity to comment on these operations and please let me know if we need to talk about this further. From: McCurnin, Mike [mailto:[email protected]] Sent: Monday, June 11, 2012 11:04 AM To: Gastineau, Janet [DNR] Subject: Altoona Connection from Southeast Polk South PWS Janet: After our discussion this AM, I thought I would follow up with a documented request. Operation of the Southeast Polk South PWS has changed significantly with the installation of large feeder mains and new elevated water storage tank. The system now has much more storage volume. While the volume is certainly beneficial from a supply perspective, balancing the dual need of adequate chlorine residuals while minimizing DBP (with changing requirements) has been challenging. Thus far we have used alternate tank set points, modified tank operations, installed on-line chlorine monitoring in 3 locations, and performed additional flushing within the system to balance the needs within the system. In addition to these measures, we have looked for provisions that would allow us to increase the water demand on the system in either temporary or permanent fashion. • Portions of the DSM PWS (in Pleasant Hill) have been permanently merged into the Southeast Polk South PWS to increase number of service connections. • A control valve has been installed at the Pleasant Hill Booster Station that will allow water to flow (seasonally) from Southeast Polk South back toward the Pleasant Hill and the Des Moines PWS. In time, we may elect to make this a more permanent part of our operation. • Lastly, we have been working with Altoona on a connection to the Southeast Polk South PWS. Altoona has installed a new water main and control valve and is ready to commission this connection. Adding this water demand will certainly help us in our efforts to balance chlorine levels and manage DBP issues. Knowledge of chlorine levels at this new connection point are somewhat unknown. Rather than install monitoring equipment and any additional chemical feed equipment at this connection point, we request an initial test window be established (60 to 90 days perhaps) whereby entry point grab samples could be taken. Should chlorine levels be less than 0.3 mg/L (free chlorine) in the grab sample, additional microbiological analysis would be performed (HPC) and reported. HPC results in excess of 500 cfu/ml would result in other measures to restore chlorine residuals. At/near the end of the test window, final decisions could be made by Altoona, DMWW, and DNR regarding the need and/or location of any monitoring or feed equipment. Your consideration of this request is certainly appreciated. JANET GASTINEAU
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