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042109 E-mail from Mark Flury with SD revisions.htm MessagePage of ?? From: Mark Flury \[mflury@flurywyrick.com\] ? Sent: Tuesday, April 21, 2009 2:24 PM To: Shuster, Jerry Cc: McConnell, Jeanie; Bob Murphy; Doug Bratz Subject: RE: Willowdale Townhomes SD Conflict Hi Jerry, Attached please find a revised vault outfall profile with 0.1 ft of fall between the referenced structures as requested. Ive also attached the stormwater modeling result of this new scenario. The two detention vaults will ? behave hydraulically as one vault. There is negligible friction loss in the 18pipe between the two vaults and no ? restrictor on the westernmost vault; therefore they would not behave as vaults in series. I could establish a stage ? storagedischarge relationship for the western vault to allow level pool routing from the west vault to the east ? vault, however, the 18pipe would not restrict any stormwater. The west vault is dependent on the control ? structure, therefore they behave as onevault. ?? The increased pipe slope results in a new volume of 5,109 cf. This volume still exceeds the design volume of 4,774 cf that is required to match the predeveloped forested release rates. The attached modeling results represent the new outfall configuration. You will notice that the redesigned restrictor still mitigates the design storms as required with extra capacity in the vault (maximum water surface of elevation of 437.45 vs. 437.70 provided). Please also note that the predeveloped forested release rates are a vast improvement over the previously developed site which was nearly entirely impervious and provided no detention nor water quality. Please advise me as to whether the proposed changes are acceptable at your earliest convenience. Thank you, Mark Mark Flury, P.E. FluryWyrick & Associates, Inc. ? 3409 McDougall Avenue, Suite 102 Everett, WA98201 Ph: 4252590964 ?? Fax: 4252592189 ?? Cell: 4253156160 ?? From: Shuster, Jerry \[mailto:shuster@ci.edmonds.wa.us\] Sent: Tuesday, April 21, 2009 10:28 AM To:Mark Flury Cc: McConnell, Jeanie Subject: RE: Willowdale Townhomes SD Conflict Mark, I've consulted with the City Engineer and Jeanie on your issue. We do not want a flat pipe in the rightofway. Can you resubmit a drawing that shows the pipe from CB2 to CB1 and CB 1 ??? to the existing manhole with at least .1 ft between CB2 and existing. Also, given this change in the control structure outlet invert, provide a replacement drainage plan that models this new condition. I would like to see the modeling done in way that matches your design of two separate vaults in series, with the flows routed from vault 2 to vault 1, to the control structure and then discharge to the City system (not just modeled as one large vault). As you know, this site drains to Hall Creek and then LakeBallinger. The City is currently involved in "high profile" project working with five other jurisdictions on past flooding and water quality issues in the Lake, so I need to ensure the redesign of the detention system meets the ? standards to the extent possible and document it. Call me if you want to talk about this more. Thanks, file:///C:/Users/cockrum/AppData/Local/Temp/042109%20Email%20from%20Mark%20Fl...7/5/2017 ? MessagePage of ?? Jerry Shuster, P.E. Stormwater Engineering Program Manager City of Edmonds 121 5th Ave N. Edmonds, WA98020 Desk Phone: 4257710220 x1323 ?? Fax: 4256725750 ?? shuster@ci.edmonds.wa.us -----Original Message----- From:Mark Flury \[mailto:mflury@flurywyrick.com\] ? Sent: Monday, April 20, 2009 11:11 AM To: McConnell, Jeanie; Shuster, Jerry Cc: Bob Murphy Subject: RE: Willowdale Townhomes SD Conflict Hi Jerry, When we spoke on Friday afternoon, you thought you might have an answer this morning on the proposed storm outfall revision. Is this still the case? Thank you, Mark Mark Flury, P.E. FluryWyrick & Associates, Inc. ? 3409 McDougall Avenue, Suite 102 Everett, WA98201 Ph: 4252590964 ?? Fax: 4252592189 ?? Cell: 4253156160 ?? From: McConnell, Jeanie \[mailto:Mcconnell@ci.edmonds.wa.us\] Sent: Friday, April 17, 2009 6:34 AM To: Shuster, Jerry Cc:Mark Flury; Bob Murphy; Doug Bratz Subject: FW: Willowdale Townhomes SD Conflict Jerry, Willowdale Townhomes project is at the intersection of 208th & 76th Ave W. They ran across some utility conflicts yesterday while trying to install the storm outfall. Can you please review the email below for ? comment. I will pull the storm drainage report for you as well. Please let me know if you need any additional information from their engineer. If their proposal seems acceptable I will have them submit a revised drainage report that incorporates the new data, as well as pertinent plan sheets. Thank you, Jeanie -----Original Message----- From:Mark Flury \[mailto:mflury@flurywyrick.com\] ? Sent: Thursday, April 16, 2009 3:49 PM To: McConnell, Jeanie Cc: Bob Murphy; Doug Bratz Subject: Willowdale Townhomes SD Conflict file:///C:/Users/cockrum/AppData/Local/Temp/042109%20Email%20from%20Mark%20Fl...7/5/2017 ? MessagePage of ?? Hi Jeannie, I met with Bob Murphy and representatives from UniversalLand this afternoon to discuss a storm drainage conflict that has become apparent on the subject site. I understand from talking to Bob that you have a cursory understanding of the problem. I have attached a revised profile sheet that depicts the location of th the conflicts in 76 Ave and our proposed solution which consists of a revised detention vault outfall. The conflict is between the storm outfall and an existing concreteencased fiber optic bank and an existing gas ? main. The top elevations of these two utilities are located at elevations 433.42 and 433.52 respectively. The proposed revision consists of running the storm outfall above the conflicts at a flat slope. The head that will be produced by the vault will regularly flush the outfall pipes and it is unlikely that sediment will accumulate. The raised outfall will obviously result in a loss of live storage volume. The vault control structure invert would be raised exactly one foot. The area of the vaults is 1,310 sf and the required vault volume is 6,683 cf. The raised invert would therefore result in a loss of 1,310 cf of volume resulting in a reduction to 5,373 cf. The design volume needed to meet the required release rates was 4,774 cf (see Sheet C12 and drainage report). This was increased by a 40% safety factor per the 1992 DOE Manual. With the proposed reduction in the required volume from 6,683 cf to 5,373 cf the safety factor is reduced from 40% to 13%. This safety factor reduction is somewhat mitigated by the fact that the safety factor is intended, in part, to compensate for the SBUH methodology which tends to overestimate peak flows from pervious areas in the predeveloped condition, not taking interflow into account as the HSPF model does. ? Given the fact that this site was nearly entirely impervious in the predeveloped condition and the design ? proposed to mimic forested release rates, the loss of a portion of the safety factor will not dramatically affect the overall improvement to the downstream drainage system that this development will affect. The existing storm drainage system drains to the south at approximately 0.5% for at least 300LF; therefore reconstructing the existing system to a greater depth and flatter slope does not appear feasible. Please advise me at your earliest convenience as to whether this proposal is acceptable as the contractor is currently working onsite. ? Thank you, Mark Mark Flury, P.E. FluryWyrick & Associates, Inc. ? 3409 McDougall Avenue, Suite 102 Everett, WA98201 Ph: 4252590964 ?? Fax: 4252592189 ?? Cell: 4253156160 ?? file:///C:/Users/cockrum/AppData/Local/Temp/042109%20Email%20from%20Mark%20Fl...7/5/2017 ?