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HomeMy WebLinkAbout2021-09-15_Olson_RE_ (MH) LO stormwater_middle housing_ bobandma aroman tin morn„ Subjam Re.(Mir)CO#om:wrtx/mIddle WIMP' Date. Wednesday,September 15,101111,06.11 PM Carole, Thanks for sending over these comments. I think it will be important to have the Committee understand that on-site stormwater management does not necessarily mean that all of the rainwater in filtrates the soil at the site-other people may have that understanding as well.This is relevant to the Committee's conversation around potentially limiting die development of impervious surfaces in that folks should understand that existing stormwater code and lot coverage limitations don't really address rainwater infiltration on-site As we've discussed,changes to the stormwater code/budding code are unfornmately not within the scope of the Committee's work,and 1 agree that:Cs not a great idea m re-work the code at this time There are many concepts and details regarding the way the stormwater code functions that require more onboardmg and education for us M properly evaluate thus mprc,but-again-the general need for more on-site rainwater infiltration is an important concept for the Committee to understand. Thanks again, Erik Olson Senior Planner City of Lake Oswego PO Box 369 Lake Oswego,OR 97034 tel.503.697.6524 Stay Connected I Facebook I Twiner I Instagmm I e-updates ---Ongmal Message-- From:Randy Arthur[Inailtn'rnndvxllmnmmail tint Sent Wednesday,September 15,2021 635 AM To:f fhcarole@europocom Co bobandmignon@comcasi.eet,Olson,Erik<eolson@m.oswego.or us> Subject:(MH)LO stormwater/middle housing? Hi Carole, Thank you for your detailed comments I appreciate it Randy ---Original Message-- From:tooth-carols@europa.com rm,in,.fa.s srol.��,roira r oil Sent Tuesday,September 14,2021 5 32 PM To:randyarthur7@gmad.com Cc bobandmignon@comeasi.net,eolsou@ci oswego or us Subject(MH)LO stormwater/middlc housing? To'Chair Arthur Re Smrmwater,Middle Housing Commmee Key Issue#3 Memo On the agenda for the upcoming Middle Housing Committee Sept 15th meeting rs Stormwater,Questions and Answers and Deliberations In order ko have substantive deliberations on the details of the amount of impervious surfaces on a lot and the subsequent impacts,the committee needs a functional understanding of how stormwater and development currently works within Lake Oswego's framework. Looking to the Key Issue 43 Sloamwater Memo for understanding,I read: "The smnnwater cede requires that new developments and all development pro oois over a certain size manage all si0mrwater on the lot 1 brought ibis issue forward in my email dated August 17th,2001 that is ported on the MH website. e link hops//hnkprotect.cudasvc.comlurft a—hops%35%2P/2fivww ci oswego or us%2fWebLrnk%2fDocVrew aspx%3fid%3d1860136%26dbid%3d0%26repo%3dCity&rnE,1,0_OrUNybewT3LuudVADYcovXeZOKhF43E04931KF/iFTgv4QVNTUJPu3XT1O258cEyP5R3z9]upO]1kIS6artMOSkgo]IdvuiOk]P6IEIyKh4&typo-1 OtLakerswego The statement that new developments manage all stormwater on the lot does not seem to follow the reality of a new build in FANFH that was examined and approved by staff.Staff has said "With respect to the specific situation you are referring to,I'll just quickly point out Art dime pipes are part of the design of stonnwater facilities to generally ensure that post-development runoff rates do not exceed pre-development runoff rates,one of these pipes manages stormwater discharge from the lot,and the other is an emergency overflow for when the facility is clogged The owner is generally responsible for making sure the facility operates correctly and are required to sign a maintenance agreement which runs with the land." I went with the new build's smmiwater report in hand to a local soils geologist What I beamed was that the stormwater on ibis site in FANFH is bemg treated onaite during a small rain event,but NOT managed emote To state that water is bemg managed onsrte requires the water to go back into the soils onsite.In this new build in progress,the water is being treated by being filtered through gravel,sand and plantings in a completely enclosed cement cistern adjacent to the full basement of the home,and then it is discharged into a gully that slopes down into Tryon Creek For the basic physics,think swimming pool with a dram into a gully that slopes roe Tryon Creek There is no design in the system that snows for the water to infiltrate into the Doane soils In the event of prolonged heavy rains and the cement cistern having reached rapacity,the water directly releases through a pipe into the gully without any st0nnwater treatment at all,to avoid spilling over the top of the cistern on t0 the home site. I am not looking for us to rework our stormwater code.What I am saying is,as we look k0 siting middle housing,duplexes,mplexes,quadplexes,mwohomes and cottage clusters on heretofore single family lots,the Middle Housing Committee must have as accurate understanding of how stormwater regulations currently direct di in es a of developmentrp in Lake Oswego and how our city staff and unplement those stormwater regulations If our current stormwater regulations only require siormwater be treated onsite and permit all discharge offsite,then we need to know that becau ewe need to plan for potential impact to surrounding properties Or we need to write stronger budding code,understanding that our stormwater code is not going to hold water Thank you Carole Ockert Below is a copy of as email I have sent to Ryan Lentz in the Engineering Dept.to get specific answers. Hi Rya I have a 2 very simple questions 1 I bane had a geologist review the system design for stouowater for 977 9th and have been informed that the system does not infiltrate any water into the site at all.Can you confirm that as designed this particular cement cistern system does not infiltrate any stormwater min the ntev 2 HMIs lot had no access to the gully,would you have allowed the same sized development to be bulk on the site' Thanks, Carole Carole Ocken, FANFH Land Use Larson and Middle Housing Citizen Advisory Committee representative from the Neighborhood Chairs Committee