City of Vancouver Planning By-law Administration Bulletins

Transcription

1 City f Vancuver Planning By-law Administratin Bulletins Planning, Urban Design and Sustainability Department 453 West 12th Avenue, Vancuver, BC V5Y 1V4 tel: 3-1-1, utside Vancuver fax: website: vancuver.ca planning@vancuver.ca app: VanCnnect Rainwater Management Bulletin Authrity - Directr f Planning Effective July 11, 2018 In this Bulletin, the fllwing definitins apply: Green infrastructure means an apprach t water management that mimics the natural water cycle by reducing and treating rainwater at its surce while delivering envirnmental, scial, and ecnmic benefits. Rainwater means rainfall and ther natural precipitatin. Best management practice means cmmn best practices t imprve rainwater management. Rainwater drainage means runff that is the result f rainfall r ther natural precipitatin r frm melting snw r ice. Rainwater Management System means a system fr cllecting, retaining, detaining, treating and cnveying rainwater and rainwater drainage. The system may include: catch basins, sewers, pumps, facilities/structures/devices used fr strage, detentin and quality treatment f rainwater and rainwater drainage (including natural ecsystem based facilities/structures/devices). The system des nt include sanitary plumbing r service cnnectins in buildings. Rainwater Management Plan means a hydrlgical and hydraulic study, certified by a Prfessinal Engineer, which sets ut a cmprehensive apprach t planning, design, implementatin and peratin f a rainwater management system in a manner that ptimizes reduced envirnmental impacts and drainage efficiency. The Rainwater Management Plan sets ut the size, lcatin and cnfiguratin f the rainwater management system n the develpment site and includes assciated methdlgy, calculatins, and drawings that demnstrate hw the requirements impsed n the develpment will be met. Intrductin Onsite rainwater management is needed t mitigate the impacts f increased yearly precipitatin due t climate change, increased develpment density, and decreased pervius surfaces that allw rainwater t infiltrate, all f which when cmbined will increase the ccurrence f excess rainwater verwhelming the sewers leading t cmbined sewer verflws. The use f water sensitive site design and green infrastructure practices r surce cntrls keeps harmful strmwater pllutants frm entering ur receiving waters and adds resiliency t the City s drainage system, which is predicted t experience wetter winters, drier summers, and mre frequent ccurrence f intense strms. July 2018

2 The purpse f this bulletin is t prvide applicants infrmatin n the prcess and required submissins related t nsite rainwater management that meets the Citywide Integrated Rainwater Management Plan (IRMP) requirements fr retentin, rate cntrl, cleaning, and safe cnveyance. Sites having a ttal site size f 8,000 m 2 r mre, r cntaining 45,000 m 2 r mre f new develpment flr area, are t fllw the requirements laid ut in the Rezning Plicy fr Sustainable Large Develpments. Rainwater Management Requirements Applicants will be required t prduce a Rainwater Management Plan (RWMP) that details hw the nsite rainwater management system meets the requirements utlined belw, prepared, signed and sealed by a subject matter expert (Prfessinal Engineer), subject t review. The applicant is t demnstrate hw the prpsed system will meet the fllwing: 1. Vlume Reductin 1.1. Capture 24 mm f rainfall in 24-hurs (r 70% f the average annual rainfall vlume) frm all areas, including rftps, paved areas, and landscape and infiltrate, evaprate r reuse it Landscape areas ver native subsils with apprpriately sized grwing medium meet the 24 mm capture requirement. See Design Resurces belw fr guidance n sizing tpsil fr rainwater management All prpsed landscape areas are t ensure adequate grwing medium fr bth hrticultural and rainwater management needs The applicant must priritize methds f capture accrding t the three tiers belw, beginning with Tier 1. Justificatin must be prvided fr using the 2 nd and 3 rd tier ptins. Sme acceptable exemptins have been utlined belw. The tiers are as fllws: Tier 1: Use vlume reducing green infrastructure practices. Acceptable practices include but are nt limited t: infiltratin int in-situ sil, rainwater harvesting and re-use, and green rfs. Tier 2: Use nn-infiltrating landscapes. Fr example, rainwater can be directed t absrbent landscape n slab, clsed bttm planter bxes, and lined biretentin systems. Tier 3: Use detentin in cmbinatin with a water quality treatment practice as a last resrt. Allwable release rate fr detentin facilities is described belw. Acceptable Exemptins Justificatins fr nt using 1 st tier green infrastructure practices will be reviewed at the discretin f the City. Exemptins may be granted but are nt limited t the fllwing reasns: Tier 1 Exemptins: Lw infiltratin capacity (e.g. less than 1.5 mm/hr); Limited available space fr engineered infiltratin systems due t nsite cnditins, such as tree retentin; Seasnally high grundwater table r bedrck within 0.6 m f the bttm f the practice; Cntaminatin cncerns; and Slpe stability cncerns (as supprted by a preliminary getechnical study, see submissin requirements belw). City f Vancuver July 2018 Rainwater Management Bulletin Page 2

3 Tier 2 Exemptins: Limited available space fr nn-infiltrating facilities due t nsite cnditins, such as tree retentin. 2. Release Rate 2.1. The rainwater management system fr the building(s) and site shall be designed such that the peak flw rate discharged t the sewer under pst-develpment cnditins is nt greater than the peak pre-develpment flw rate fr the return perid specified in the City f Vancuver s Intensity-Duratin-Frequency curve (IDF curve)(see attached IDF curves). The City f Vancuver s 2014 IDF curve shall be utilized fr pre-develpment design flw calculatins, and the City s 2100 IDF curve, which takes int accunt the effects f climate change, shall be utilized fr pstdevelpment design flw calculatins. Pre-develpment, in this cntext, means the site s immediate use preceding develpment. 3. Water Quality The water quality requirements are utlined belw. The water quality vlume t be treated varies depending n the type f pllutant generating surface The first 24 mm f rainfall frm all pervius and impervius surfaces shall be treated t remve 80% Ttal Suspended Slids (TSS) by mass prir t discharge frm the site. Fr impervius surfaces with high pllutant lads, including rads, driveways, and parking lts, the rainfall t be treated increases t the first 48 mm f rainfall. Treatment can be prvided by either ne green infrastructure practice r structural Best Management Practice (BMP) r by means f a treatment train cmprised f multiple green infrastructure practices r structural BMPs that can be demnstrated t meet the 80% TSS reductin target Vegetated practices r absrbent landscapes that infiltrate r filter the apprpriate water quality vlume (based n the type f pllutant generating surface) thrugh a minimum f 450 mm f grwing medium are assumed t meet the quality requirement. The Metr Vancuver Strmwater Surce Cntrl Design Guidelines referenced belw utlines grwing medium specificatins Fr prpsed prprietary treatment devices: Prvide prduct infrmatin fr prpsed prprietary treatment devices Prducts need t meet the abve treatment standard and be certified by either the Washingtn State Department f Eclgy s Technlgy Assessment Prtcl Eclgy Prgram (TAPE) r Envirnmental Technlgy Verificatin (ETV) Canada. The applicant may prpse ther technlgies but must prvide supprting infrmatin that shws the technlgy meets the treatment standard. City f Vancuver July 2018 Rainwater Management Bulletin Page 3

4 Design Resurces The Metr Vancuver Strmwater Surce Cntrl Design Guidelines is available as a design resurce t address the abve vlume reductin and water quality requirements, and als cntains infrmatin n cnstructin cnsideratins and staging as well as facility maintenance. ntrldesignguidelines2012.pdf Submissin Requirements At time f an applicatin t rezne a develpment site: Submissins fr an applicatin t rezne must include the fllwing elements: A preliminary Rainwater Management Plan, utlining the rainwater management apprach t be taken n site and hw the prject will meet the requirements fr vlume reductin, rate cntrl, and quality. This apprach is t infrm a detailed Rainwater Management Plan that is t be submitted prir t enactment. The Rainwater Management Plan must be crdinated with the pen space plan, site plan, landscape plans and all apprved plicies and guidelines in respect t the prject. RWMP submissins must include the fllwing elements: Pre-develpment site plan shwing rthpht, existing drainage areas, and nsite and dwnstream ffsite drainage appurtenances; A prpsed site plan that delineates building lcatin, undergrund parking extents, and drainage areas and includes the area measurements fr pervius/impervius areas. The site plan shall als identify apprpriately sized green infrastructure practices fr each f the drainage areas; Hydrlgic and hydraulic analysis prepared by a qualified prfessinal in the area f rainwater management shwing hw the site will meet the abve requirements; Justificatins fr nt using Tier 1 and Tier 2 green infrastructure practices must be included in the RWMP; Details n hw the rainwater management requirements set ut abve will be achieved thrugh any develpment phases and nce all develpment phases are cmplete; and Supplementary dcumentatin fr any prprietary prducts that clearly demnstrates hw they cntribute t and/r meet the abve requirements. A preliminary getechnical study supprting assumptins made in the preliminary RWMP, that includes the fllwing: An evaluatin f the ptential fr and risks f nsite rainwater infiltratin, such as slpe stability and sil cntaminatin; Results f infiltratin testing at likely lcatins fr infiltratin practices and a prpsed design infiltratin rate; Sil stratigraphy; and Depth t bedrck and seasnally high grundwater at likely lcatins fr infiltratin practices. City f Vancuver July 2018 Rainwater Management Bulletin Page 4

5 Prir t the Enactment f a By-law t rezne a develpment site: Every applicant will be required t prvide a final signed and sealed RWMP cmpleted by a Prfessinal Engineer, with an accmpanying final getechnical study. The cntent and supprting dcumentatin is t be updated t reflect all material changes t the prpsed develpment and new/refined supprting data, calculatins, plans, reprts and ther materials fllwing submissin f the preliminary RWMP. Specifically, the final RWMP shall include: 1. Final hydrlgic and hydraulic analysis based upn the final design f the rainwater management system; 2. Cnfirmatin that access has been prvided fr maintaining the rainwater management system, such as prviding truck access fr pumping ut sediment traps; and 3. A maintenance and peratin guide fr the rainwater management system that is prvided t the eventual wner r party respnsible fr maintenance. Prir t Develpment Permit Applicatin: Fr applicants prceeding frm a rezning: n additinal reprting n the rainwater management system is required fllwing the submissin f the final RWMP and getechnical study at the time f Enactment. Fr applicants applying directly at the develpment permit stage: a preliminary RWMP is nt required and applicants are t submit a finalized RWMP and getechnical study. Bth must include the same minimum elements described abve fr the preliminary and final RWMP and getechnical study submissins and must have been signed and sealed by a qualified Prfessinal Engineer. Applicatin Flw Diagrams Rezning Applicatins: Rezning Enquiry Acknwledgement f rainwater management and getechnical requirements Rezning Applicatin Submissin f preliminary RWMP Submissin f preliminary getechnical study Enactment Submissin f finalized RWMP Submissin f finalized getechnical study Direct Develpment Permit Applicatins (currently nly applicable in the Cambie Crridr): Develpment Permit Pre-Applicatin Acknwledgement f rainwater management and getechnical requirements Develpment Permit Applicatin Submissin f finalized RWMP Submissin f finalized getechnical study City f Vancuver July 2018 Rainwater Management Bulletin Page 5

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