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2011, 03-01 DE Email regarding grading and drainage • • Mary Swank From: Henry Allen Sent: Tuesday, March 01, 2011 5:09 PM To: 'jsaywers©whipplece.com' Cc: John Hohman; Dev Eng Subject: Shelley Lake Property at 16407 E 10th Lane Hi John, I got a copy of your email to John Hohman. The grading and drainage situation concerning this property does not have to do with the drainage studies that were performed for the Shelley Lake subdivisions but rather has to do with the regrading that occurred with the construction of the house. It appears that the site was graded such that the stormwater from the impervious surfaces flows onto adjacent properties. What we need is an Engineering evaluation of the parcel's drainage showing that the post-project conditions to the neighbors are the same (or better) as the pre-project conditions. Attached is what I gave Mr. Kelsey when he came in last October - CI Info given to Mr Kelsey-Oct2... Below is some guidance on what we would be looking for from the drainage evaluation of this property — Ct Residential ralnage Assessmen. Thank you, Henry Allen Development Engineer City of Spokane Valley 11707 E. Sprague Ave, Ste. 106 Spokane Valley, WA 99206 (509) 720-5319 (509)921-1008 Fax ha lien(Ds poka neva I lev.orq (Contents of this email and any reply are subject to public disclosure.) 1 lbil‘ (2asaeu.fia ( LiGl0 �1`'to i`? is ire- Lota� ti irk Lava- toT 2c - M9 aha r ydg `e 9 cot laxtCIT Y OF — 1 as, Vt (.014( Ott- °tr.° kg SPOKANE tW �•--� > Valley cne z ' ' 1��, ) 1,) „ ,))) 1 St OK NT Cowry SPOKANE REGIONAL STORMWATER MANUAL APRIL 2008 Prepared by: - �`� ��� � 8 Spokane County �4 1026 W.Broadway Avenue re> v`9' <$ Spokane,Washington 99260 4` (509)477-3600 J\d \)1/49"1 R7 City of Spokane 041k\ Gk`J 808 W. Spokane Falls Blvd. .01 Spokane,Washington 99201 (509)6254700 City of Spokane Valley 11707 E. Sprague Avenue Spokane Valley, Washington 99206 (509)921-1000 A special thanks to the members of the committee who dedicated their time and energy in the development of the manual: Gloria Mantz,City of Spokane Valley Kris Becker,City of Spokane Gary Nelson, City of Spokane Mike Yake, City of Spokane Colleen Little, Spokane County Matt Zarecor, Spokane County SPOKANE REGIONAL STORMWATER MANUAL CHAPTER 1 — INTRODUCTION rria • v I i . . f. • f I I • I' =�. trik-.?LIQ►i•�.f,•• __ - __��.-.._. -. : � '. -.yam-sem —�•ir+.yyf�.y Chapter Organization 1.1 Objective And Purpose 1-1 1.2 Vision Statement 1-1 1.3 Using The Stormwater Manual 1-1 1.3.1 Technical Information 1-2 1.3.2 Policy Information 1-3 1.4 Relevant Programs and Concepts 1-3 1.4.1 Underground Injection Control Program Compliance 1-4 1.4.2 Spokane Valley-Rathdrum Prairie Sole-Source Aquifer 1-4 1.4.3 National Pollutant Discharge Elimination System Compliance 1-5 1.4.4 Pollutant Generating Impervious Surface 1-6 1.5 General Requirements 1-6 1.6 Standard of Care 1-7 1.7 Severability 1-8 April 2008 Chapter 1—Introduction 1-i SPOKANE REGIONAL STORMWATER MANUAL the NPDES and the Water Pollution Control Act "Waters of the state" means all lakes, rivers, ponds, steams, inland waters, ground waters, salt waters, and all other waters and water courses within the jurisdiction of the state of Washington (Washington Administrative Code(WAC)Chapter 173-216-030(20)). In December 1999, the U.S. EPA adopted NPDES Phase II stormwater regulations, identifying municipalities that are subject to NPDES municipal stormwater permitting requirements. Federal regulations required that Phase II permits be issued by December 2002 and that designated Phase II communities submit an application for permit coverage by March 2003. The Department of Ecology issued the Eastern Washington Phase II Municipal Stormwater Permit on January 17, 2007, effective February 16, 2007, which applies to Spokane County and the Cities of Spokane and Spokane Valley. The Phase II Permit requires the development of a Stormwater Management Program(SWMP). This Manual is intended to be technically equivalent to the Department of Ecology's Stormwater Management Manual for Eastern Washington in order to meet the NPDES requirements for both permitted and non-permitted communities in Spokane County. 1.4.4 POLLUTANT GENERATING IMPERVIOUS SURFACE Pollutant generating impervious surface (PCIS) areas are significant sources of pollutants in stormwater runoff. These areas include surfaces subject to vehicular use, industrial activities, or storage of erodible or leachable materials that receive direct rainfall. The following are considered PCIS areas: roads,unvegetated road shoulders, bike lanes within the traveled lane of a roadway, driveways, hydraulically connected sidewalks,parking lots,some roofs, fire lanes, vehicular equipment storage yards and airport runways. Please refer to Section 6-4. 1.5 GENERAL REQUIREMENTS The owner or project proponent and his agent are responsible for the following: • Coordinating project consultants • Providing complete drainage submittals • Ensuring adherence to: o The standards and criteria presented in this Manual o The Administrative Conditions of Approval,if applicable o Any conditions established by local jurisdiction staff • General project management. April 2008 Chapter 1—Introduction 1-6 SPOKANE REGIONAL STORMWATER MANUAL The owner or project proponent and his agent are required to obtain acceptance of the drainage submittal from the local jurisdiction prior to any of the following: • Final plat approval • Final short plat approval • Binding site plan approval • Issuance of a building permit • Issuance of a road approach permit • Any other land use action as defined by code, regulation or resolution of the local jurisdiction. The drainage submittal shall be prepared in accordance with this Manual,the applicable version of the local jurisdiction's design standards,the International Building Code(IBC) and the International Residential Code (IRC). The submittal shall be prepared by a professional civil engineer currently licensed in the State of Washington and shall be submitted to the local jurisdiction for review and acceptance. The rate and volume of stormwater runoff originating on any proposed land development, a Pt road or area draining to, across or through the project site shall be estimated in accordance with the criteria presented in this Manual. These estimates shall be the basis Q'1 of the drainage report. Unless specifically approved by the local jurisdiction, the peak rate and volume of stormwater runoff from any proposed land development to any natural or constructed point of discharge downstream shall not exceed the pre-development peak rate or volume of runoff. A down-gradient analysis demonstrating that there will be no acwr expected adverse impacts on downgradient properties will be required. Exceptions with 117045 regard to rate and volume control can be made for regional facilities planned by the Iocal jurisdiction. Stormwater runoff from a developed site shall leave the site in the same manner and ''` location as it did in the pre-developed condition. Flow may not be concentrated onto te' down-gradient properties where sheet flow previously existed. Drainage shall not be diverted and released downstream at points not receiving drainage prior to the proposed development. 1.6 STANDARD OF CARE The standards presented in this Manual should be considered the minimum requirements to be used in the design of stormwater facilities. Due to special site conditions, environmental constraints, or other applicable laws, stormwater management designs may frequently need to exceed the minimum requirements. It is incumbent upon the engineer to use good engineering practice and to be aware of,and implement,new design practices and procedures that reflect current techniques in stormwater design, providing sufficient measures to ensure that the drainage facilities function as intended. Good April 2008 Chapter 1—Introduction 1-7