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HEX Rsp to Third Continuance-Part 3 100814Project To: From: Subject: CC' Date: N.L. OLSON & ASSOCIATES, INC. Engineering, Planning & Land Surveying 2453 Bethel Avenue Port Orchard, WA 98366 P. 360-876-2284 / F.360-876-1487 www.nlolson.com TECHNICAL MEMORANDUM BGH, LLC, Rolling Sunrise Preliminary Plat Alan Wallace — Attorney at Law, Williams Kastn Norman L. Olson, P.E. — N.L. Olson & AssociatE Comments as Allowed by 3RD Continuance Pat Ebert October 8, 2014 N.L. Olson & Associates, Inc. (N.L. Olson) provides this Technical Memorandum (TM) to supplement review comments provided in the prior TMs prepared by N.L. Olson dated September 10, 2014 and September 22, 2014. These additional comments are allowed by the Hearing Examiner's issuance of a Third Notice of Continuance dated September 26, 2014. This TM provides further comments in regards to Stormwater Management as allowed by the Order. In regards to disagreement whether the plat development must strictly comply with the Minimum Requirements stated in the WDOE 2005 Stormwater Manual for Western Washington, please see attached email communication with Ed O'Brien from WDOE. Mr. O'Brien is recognized as an authority in regards to interpretation of the 2005 WDOE Manual. He was the Technical Lead responsible for authoring and development of the 2005 Manual and he is referenced on the WDOE website as a point of contact for questions regarding both the prior and current Manuals (2005 and 2012 Manuals). Note: Copy of WDOE contact list for questions regarding the Manuals is attached as well as a copy of the Acknowledgment page from the 2005 Manual. Mr. O'Brien emphatically states that the impervious surface thresholds cannot be permissibly waived to exempt the project from compliance with Minimum Requirements in the manner proposed by the applicant. He notes to do so would subvert the regulatory intent of the Manual. Rolling Sunrise Plat Project Response to Browne & Wheeled 0-8-14 Letter Page 2 of 2 Therefore, regardless of the strategies employed to control runoff from the site, whether the standards, requirements and BMPs in the 2005 WDOE Manual or LID techniques in the Kitsap County LID Manual, the feasibility to infiltrate runoff to the ground and/or regulate runoff surface discharge must be fully ascertained. A comprehensive computer model using Western Washington Hydrological Model (WWHM) of the entire site, with all surfaces and proposed BMPs included, must be developed to demonstrate compliance with MR#7. Surfaces may be omitted or changed in nature from the model and possibly the thresholds but only as specifically allowed and infiltration facilities are not included. Appropriate and approved water quality measures must also be employed. It is true that downstream drainage systems from the site do not meet current design standards and essentially are nonexistent. It is also true that the Rolling Sunrise Project must be designed such that runoff from the project will not further impact the downstream properties adversely. The 2005 WDOE is clear in regards to runoff discharge restrictions when downstream closed depressions and flooding are involved. These restrictions can be quantified through the use of WWHM. When these restrictions are applied to this project, one will find that essentially all stormwater must be retained on-site through infiltration. Studies and data are thus needed to ascertain the feasibility to infiltrate stormwater to the ground at the project site. Demonstrating such feasibility should be accomplished based on the following: • Geotechnical assessment and report of the subsurface conditions, native soils and groundwater conditions. • Preliminary civil engineering analysis and design for storm control facilities based on computer modeling using WWHM with site and project specific parameters entered such as: o Existing site conditions including existing topography, soils, groundwater, etc. o Historic forested conditions and parameters for modeling o Post development site conditions including proposed clearing and landscaping, grading, structures, septic drainfields, surfacing, etc. It is important to note that not only do the proposed impervious surfaces need to be recognized within the WWHM model, but all surfaces associated with the project must be included. Surfaces such as landscaping and grass (potential surfaces over septic drainfield areas) are not to be omitted from the model. Although relatively pervious compared to roofs or asphalt, these surfaces must also be included in the model and compared to the historic forested conditions (old growth forest) for runoff contribution and compliance with MR V. All off-site roadway improvements that are required must also be included and recognized within the same model. Off-site improvements cannot be separated from the project in regards to stormwater mitigation. Norman Olson From: O'Brien, Ed (ECY) <eobr461@ECY.WA.GOV> Sent: Tuesday, October 07, 2014 10:07 AM To: Norman Olson Subject: RE: Avoiding Compliance with Minimum Requirements 6 - 10 Mr. Olson, Thanks for the question. It was not the intent of the 2005 West. Wash. Stormwater manual to use the infiltration exemption imbedded within M.R. #7 when making the threshold determinations. To make a claim that it should be used, and then to allow engineers to use whatever methods they want to make that claim is preposterous. It subverts the regulatory intent. So, don't use the infiltration claim for the threshold determination. Once the project has triggered MR #7, then they have to use the approved engineering methods to demonstrate that they can remove certain surfaces from the modeling requirement. For instance, proper application of BMP T5.10A would allow a roof to be removed from the WWHM calculations for demonstrating compliance with MR #7. Also, use of BMP T5.30 allows the designer to remove all of the area that drains to the preserved area from the computer model. However, other LID BMPs, such as bioretention (BMP T5.14B), permeable pavements (BMP T5.15), downspout dispersion (BMP T5.10B), must still be entered into the model so that the model predicts their performance. For the threshold determination, the 2005 manual (see "supplemental guidelines" on page 2-11 of Volume 1) does allow surfaces to be considered as recommended in the LID modeling credits — where those credits allow modeling as landscaped area, 50% landscaped area, or pasture. It does not refer to infiltration facilities. Please note that the guidance concerning use of the modeling credits when making the threshold determination was purposefully deleted from the 2012 manual. Ed O'Brien From: Norman Olson [mailto:nlolson2@nlolson.com] Sent: Friday, October 03, 2014 2:28 PM To: O'Brien, Ed (ECY) Subject: Avoiding Compliance with Minimum Requirements 6 - 10 Hello Mr. Obrien: I know you are very busy but I have a question needing clarification and I'm not sure who else I would ask. I am reviewing a preliminary drainage plan for a project and have a question about the developer's interpretation of the threshold determination. Although the 3.5 acre project will create significant amounts of impervious surface, well beyond 5000 sf, the developer's engineer believes that, "Since the runoff from the entire roadway and lot improvements is directed to 100% infiltration facilities, those areas can be removed from the threshold determination. Therefore, our report states that there is no new impervious area over thresholds and only Minimum Requirements (MR) 1-5 are applicable". On this basis, their proposed design of infiltration facilities and the infiltration rate testing protocol does not comply with the requirements of the 2005 manual that is adopted by the governing jurisdiction, i.e., MRs 6 & 7 are avoided. The reason they say this is allowed is because they believe the governing jurisdiction has adopted a policy that impervious areas conveyed to facilities that infiltrate 100% can be given the same credit for threshold determination as impervious areas managed by Low Impact Development practices. If indeed this is the jurisdiction's policy, it would seem to be unwritten. The 100% infiltration storm system they propose is simply directing storm runoff from gravel roadways through a narrow grass shoulder (2 or 3ft wide) and into an infiltration ditches. They do also propose the use of bioretention cells for individual lots. Because they are avoiding MRs 6 & 7, the subsurface soil and groundwater assessment, design analysis and design criteria is far below the standard required by the 2005 manual. In fact, I don't know that any soil assessment has been conducted. The downstream constraints from this project are considerable so this is even more important. The question: If one simply proposes to infiltrate 100% of runoff, can the associated impervious areas be credited from threshold determination and thus avoid MR's 6-10? Thank you for your time. Norman L. Olson II, P.E. N.L. Olson & Associates, Inc. 2453 Bethel Avenue Port Orchard, WA 98366 360-876-2284 Office 360-620-3438 Cell nlolson2@nlolson.com Electronic Privacy Notice. This e-mail is confidential and intended solely for the use of the addressee(s) named above. if you are not the intended recipient, please be advised that you are legally prohibited from retaining, using, copying, distributing, or otherwise disclosing this information in any manner. if you have received this e-mail in error, please promptly notify the sender and immediately delete it. Thank you. 2001 Stormwater Management Manual for Western Washington Page 1 of 1 Ecology home > Water quality - Stormwater Management Manual for Western Washington > Who to Contact for Technical Information Who to Contact for Technical Information General Questions Amanda Heve Department of Ecology 360-407-6457 PO Box 47600 Olympia WA 98504-7600 Volume I - Minimum Technical Requirements Ed O'Brien Department of Ecology 360-407-6438 PO Box 47600 Olympia WA 98504-7600 Volume II - Construction Stormwater Pollution Prevention Doug Howie Department of Ecology 360-407-6444 PO Box 47600 Olympia WA 98504-7600 folume III - Hydrologic Analysis and Flow Control BMPs Foroozan Labib Department of Ecology 360-407-6439 PO Box 47600 Olympia WA 98504-7600 , Volume IV - Source Control BMPs Dan Gariepy Department of Ecology 360-407-6470 PO Box 47600 Olympia WA 98504-7600 Volume V - Runoff Treatment BMPs Ed O'Brien Department of Ecology 360-407-6438 PO Box 47600 Olympia WA 98504-7600 44� Copyright © Washington State Department of Ecology. See http://www.ecy.wa.gov/copyright.html. http://www.ecy.wa.gov/programs/wq/stormwater/manualcontacts.htmi 10/6/2014 Acknowledgments The individuals listed below volunteered their time and knowledge to aid in the 2001 update of this volume of the Department of Ecology's Stormwater Manual. The department thanks the members of the Volume I Committee for their efforts and advice. Name Affiliation Lisa Austin Department of Ecology Peter Birch Washington Department of Fish & Wildlife Mark Blosser Olympia Public Works Department Bert Bowen Washington Dept. of Transportation Randy Brake Pierce Co. Water Programs Paul Bucich Pierce Co. Surface Water Management Dana Carlisle Geoengineers, Inc. Robert Chandler Seattle Public Utilities Michelle Cramer Washington Department of Fish & Wildlife Bruce Dodds Dodds Consulting Engineers Darla Elswick Seattle Public Utilities Nathan Graves Kennedy/Jenks Consultants Terra Hegy Washington Department of Fish & Wildlife Doug Hennick Washington Department of Fish & Wildlife Julie Howell Kennedy/Jenks Consultants Tom Holz SCA Engineering Gary Kenworthy City of Port Angeles Nancy Malmgren Carkeek Park Watershed Dan Mathias Everett Public Works Department Ralph Nelson Entranco, Inc. John Rogers CH2M Hill Jeffrey Stern King Co. Department of Development and Environmental Services Steve Worley Spokane County Public Works Bruce Wulkan Puget Sound Water Quality Action Team Department of Ecology Technical Lead Ed O'Brien��r Technical Review and Editing Economic and Engineering Services, Inc. — for the 2001 update Charlene Witczak — 2005 update Kelsey Highfill — 2005 update February 2005 Volume 1— Minimum Technical Requirements