From: Jennifer Cline
Sent: Fri Jun 26 14:20:57 2015
To: Dan Huff
Cc: Christine Hein
Subject: FW: Report updates
Importance: Normal
Attachments: image001.gif; text-6-26-15(1).docx; Attachment E-tables(5).xlsx; fyi Jennifer Cline, P.E. City of Molalla Public Works Director O: 503.759.0218 F: 503.829.3676 -----Original Message----- From: Fasth, Bill [mailto:bfasth@BrwnCald.com] Sent: Friday, June 26, 2015 2:20 PM To: Phillip Bender Cc: 'Jennifer Cline'; Laffitte, Dan Subject: Report updates Phil, The most updated versions of the report and tables are attached. The updated report is based primarily on the version that I emailed to you yesterday. Regarding the marked-up version that you sent to me this morning, I have not incorporated most of your comments based on our phone conversation earlier today. As I stated in the phone call, there is only one approach (a mass balance approach) that we used for reach our conclusion that about 1,000 gal entered Bear Creek. Within one part of that approach (the part where we estimated the volume of wastewater pumped to lagoon 1 to be 536,728 gal), we did a cross-check to see if our method for estimating this volume seemed ok or not. The method that we used to estimate 536,728 gal is described in the section entitled "Pumping of Wastewater to Lagoon 1 during the Incident" (refer to the bullets in this section). The method involved estimating the area of the overflow footprint when each pump event began and multiplying this area by the depth that wastewater dropped in the Parshall flume (estimated from the strip chart) during each pump event. The cross-check that we did was to see how long it would have taken the transfer pumps to pump our estimated volumes up to lagoon 1. We concluded that each pump event would have been relatively short (10 minutes or less) and that these calculations were generally supported by the strip chart that showed each pump event occurring over relatively short periods of time. Therefore, we did not feel a need to change our original method for estimating the total volume of wastewater pumped to lagoon 1 (536,728 gal). The report will not answer all questions that DEQ may have. But the approach, estimation methods, and assumptions that were used to reach our conclusion are listed throughout the report. If DEQ has questions or challenges with any other of these things, they will let us know. Although BC is not willing to assign a level of confidence to our conclusion that about 1,000 gal entered Bear Creek, our calculations indicate that this was a conceivable outcome. When I first began the review, this was not a conceivable outcome as I was calculating that the berm would have needed to be about 7 feet tall to contain all of the wastewater that entered the AB during the incident. So other mechanisms for storing the wastewater at the WWTP had to be considered (i.e. pumping of wastewater to lagoon 1, storage in the soil). These storage mechanisms are real and I believe they did occur during the incident. The overall objective of our evaluation was to see if our numbers could support, more or less, operator observations from Monday morning when they only observed a slow trickle of wastewater entering Bear Creek. We concluded that our numbers could support the operator observations. If DEQ wants to challenge us on that, then maybe some follow-up work or meetings will be needed. Bill Bill Fasth 6500 SW Macadam Avenue, Suite 200 Portland, Oregon 97239 bfasth@brwncald.com<mailto:bfasth@brwncald.com> Cell 541.602.9110 [Description: http://help.bc.com/BC_logo_2line_prple.gif]<http://www.brownandcaldwell.com/>
