Field Office Compliance - Assistance

Assistance ID - 123645
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
4/19/2022 Re: DMWW McMullen Finished Turbidity Spike Inbox Pickens, Aaron Mon, Apr 18, 1:37 PM (18 hours ago) to me, Taroon, Bob, Anne Janet - I would concur. The data they provided suggests that this is one of those "blips" due to the issue with the HSP. No spike in IFE would support this as well. If it was my system, I would invalidate this and take no further action. Thanks, Aaron iowadnr.gov AARON PICKENS | Environmental Specialist Senior Iowa Department of Natural Resources Environmental Services Division - Field Office #6 Office: 319-653-2135 - Cell: 319-461-8277 1023 West Madison St., Washington, IA 52353 On Mon, Apr 18, 2022 at 12:29 PM Gastineau, Janet <[email protected]> wrote: Yesterday they had a HSP shut off (spontaneously rather than the VFD shutting it down). This morning they were trying to figure out why and they had a spike as you can see below. The CFE monitoring point for compliance is on the common suction header for the HSP. They believe high velocity water stirred something up on the suction side and got into the turbidimeter vial because the check valve was held open. I've already told them that because of the specific explanation and good plant performance I wouldn't consider it a Tier 1 treatment technique violation, but I'm wondering what you think about a TTV with Tier 2 PN (30 days). We've held pretty firm to these exceptional events in the past with DMWW. What I would really like to do is let it go (considering the pending rule changes) since there were not two 15 minute spikes above 1 NTU, but I don't want to do that without concurrence. Please let me know your thoughts. Thank you! JANET GASTINEAU
4/19/2022 Suggested text welcome to driveConversation opened. 1 read message. Skip to content Using State of Iowa Mail with screen readers in:sent 1 of 36,871 Re: McMullen Finished Turbidity Spike Gastineau, Janet <[email protected]> 7:50 AM (15 minutes ago) to Nathan, Mike, Josh I will invalidate the data and not issue a treatment technique violation. Thank you for reporting the incident and please continue to do so. I hope you were able to resolve the problem. On Mon, Apr 18, 2022 at 12:22 PM Gastineau, Janet <[email protected]> wrote: Thank you for the documentation. Since the explanation for the spike is clear and specific and unrelated to plant performance prior to the CFE compliance point, I am not considering this a Tier 1 treatment technique violation. However, consistent with how the Iowa DNR has dealt with such spikes in the past, I will be consulting with a few individuals in order to consider issuance of a treatment technique violation requiring Tier 2 PN, which would be within 30 days. On Mon, Apr 18, 2022 at 10:29 AM Casey, Nathan <[email protected]> wrote: Janet, As we discussed on the phone, we had a finished water turbidity spike at McMullen today. While testing high service pump 1, it failed which causing a rapid drop in pressure. When pumps fail like this it is common for us to get small spikes in turbidity. This time, shortly after this pressure drop we got a spike in turbidity to over 1.0 NTU for approximately 13 min. Our 15 minute turbidity reading would show a turbidity over 1.0 NTU. This spike in turbidity is associated with the failed high service pump allowing water to flush backward causing high velocity to resuspend sediment which is are then pumped into the turbidimeter. Staff was onsite and was quickly able to address the issue, but we did still see a spike in turbidity. For the 24 hours before this event the highest turbidities were as follows: Filter 1 effluent: 0.078 NTU Filter 2 effluent: 0.024 NTU Filter 3 effluent: 0.024 NTU Filter 4 effluent: 0.075 NTU Filter 5 effluent: 0.026 NTU Filter 6 effluent: 0.029 NTU Filter 7 effluent: 0.046 NTU Filter 8 effluent: 0.076 NTU Midpoint: 0.058 NTU Looking at these turbidities we do not believe the high finished reading we got today is representative of the treatment plants performance. We also know that under new turbidity rules, the department is working on, this would not be considered an event, but I wanted to let you know it happened. Please see the enclosed trend. Let me know if you have any questions or comments. Thank you, Nathan Nathan Casey, P.E. | Director of Water Production Des Moines Water Works | WATER YOU CAN TRUST FOR LIFE 2201 George Flagg Parkway | Des Moines, Iowa 50321 | www.dmww.com Phone: (515) 283-8709 | fax: (515) 283-8757 | e-mail: [email protected] JANET GASTINEAU
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