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HomeMy WebLinkAboutSWP272095 Short Plat (SHPL # ) REQUEST FOR PROJECT# Prelim. Plat (PPH ) CAGN To: Technical Services Date rcb Z U 11Y93 WOu 8 7 4/ 5 Green# From: Plan Review/Project Manager /)6 5 Project Name 57vu CfovcQ Pluct Plu7 (70 clu tactm max) Description of Project: 14 5 6yy p/evt - Itzw 5�t`Ge� rv� nroJGlueu� � Circle Size of Waterline: 10" 12" Circle One: New or Extension Circle Size of Sewerline: / 8" / 10" 12" Circle One: New or Extension Circle Size of Stormlirle: 12" 15" 18" 24" Circle One: New or Extension Address or StreetName(s) Zr400 !UE /<� "ti 5-tveert Dvlpr/Contractor/Owner/Cnslt: GarNUJcs�` QcydooH(eN-t (70 cluuma s nua) Check each discipline involved in Project Ltr Drwg N of sheets per discipline Trans-Storm h�py fl2 �eK�oy ✓ _ /D 5(Roadway/Dra;nage) (Offsite unprovememsXtnclude basin name) (include MSC sheets) Transportation (Sigtwlvafim Chma.,,at,, on.Lighting) -- / ✓ 3 skee�s . Wastewater NO,-th 5 J (Sam(ary Sewer Ma )(Include basin name) lJ Water (Mains.Valve;Hydrants) _ ✓ (� S /(Include composite&Horizontal Ctrl Sheets) TS Use Only L/d —Oro C� 5 /S AO 9 S - TRD ^al - �09 T- d.o9 9s 0- aogs dogs � d AlApproved ey TSM Date: • 3 rom stmisd92-M.DOC/CD/bb S /KrwW PL,t 4 ,PL' F I '- „ ,} CITY OF RENTON Planning/Building/Public Works Department Earl Clymer,Mayor Gregg Zimmerman P.E.,Administrator August 8, 1995 Mr. & Mrs. Lassere 1611 Dayton Ave NE Renton, WA 98056 SUBJECT: Revision to Bioswale System for Stratford Place Plat Dear Mr. & Mrs. Lassere, We have reviewed your request to modify the drainage control system for the Stratford Place Plat to allow for construction of a deck over the existing bioswale in your backyard. The bioswale was constructed as part of the drainage system for the plat, and provides water quality treatment from the runoff from Dayton Ave NE prior to discharge to an infiltration system. The City of Renton has adopted the King County Surface Water Manual for design standards for drainage facilities. These standards include the requirement for biofiltration swales for new streets, such as this section of Dayton Ave NE. The City Code also allows for administrative modification of these standards if certain conditions are met. We have reviewed this proposal under this Modification process, and have determined that your request can be granted, subject to certain conditions. In order to modify the swale area as requested, the following items will be required: • The swale area must remain unimpeded to allow for continued flow of water from the street catch basins to the infiltration system. • The swale area shall be cleared of all vegetation, and replaced with large course crushed rock, with a minimum depth of 2 inches. • The deck must be constructed in such a manner to allow for access to the swale area underneath the deck for inspection and maintenance. • Plans for the deck must be provided to the City for review and approval prior to construction. The deck construction must also be inspected and approved by the City. Failure to comply with this requirement may nullify this modification approval, resulting in reestablishing the requirement for the biofiltration swale. „ • The catch basins in the street must be inspected by City to verify that the oil/water separator provisions remain in place, as shown on the approved as-built plans for the project. The Drainage Code Modification Process is defined in Section 4-22-16(B) of Renton City Code as follows: 200 Mill Avenue South - Renton, Washington 98055 9 This paper conlunns 5 %recycled material,25%poet consumer August 21 , 1995 Page 2 4-22-168. Modifications: Whenever there are practical difficulties involved in carrying out the provisions of this Section, the administrator may grant modifications for individual cases provided he/she shall first find that a special individual reason makes the strict letter of this Code impractical, that the modification is in conformity with the intent and purpose of this Code, and that such modification: 4-22-1681. Will meet the objectives and safety, function, appearance, environmental protection and maintainability intended by the Drainage Code requirements, based upon sound engineering judgment. 4-22-16B2. Will ndt be injurious to other property(s) in the vicinity. The practical difficulties in this particular case have been demonstrated by the resulting unsightly bioswale in the backyards of two new residential houses. The biofiltration Swale has deteriorated into a drainage ditch which no longer functions properly as a water quality facility, and detracts from the amenity value of the residential yards that home owners can reasonably expect. The photographs provided, as well as a visit to site, confirm that the bioswale has not remained green and attractive as originally designed, due in large part to the level site and the required liner under the grass area of the Swale. The intent of biofiltration swales is to provide water quality treatment of surface runoff from paved surfaces subject to vehicular traffic, such as parking lots and streets. They are typically required for treatment of runoff prior to discharge to creeks, streams, rivers, lakes, or other bodies of water. In this case, the outfall from the plat drainage is not to an open body of water, but to an infiltration system. The site is located in Zone 2 of the aquifer, and does require water quality treatment to remove oils and other non-soluble contaminants prior to release from the infiltration system. This particular drainage system was designed with oil/water separators within the catch basins of the street, which provide the necessary water quality treatment prior to infiltration. It is our determination that these oil/water separators provide adequate water quality treatment for this system, in lieu of the additional biofiltration Swale. Modification of the Swale by covering it with a deck can be accomplished while meeting the objectives of safety, function, appearance, environmental protection and maintainability intended by the City Code, and will not be injurious to other properties. In summary, your request to revise the biofiltration Swale in your backyard is approved, subject to the above listed conditions. If you have further questions regarding this matter, please contact Neil Watts at 277-6178. Sincerely, Gregg ZifYlmerman, Administrator Planning/Building/Public Works Department str-biol Pc: Ron Olson Ron Straka Neil Watts