Spokane Municipal Code

Title 17D City-wide Standards

Chapter 17D.060 Stormwater Facilities

Section 17D.060.010 Purpose/Findings

1. Purpose.

The purpose of this chapter is to identify and to the extent it is practical and financially possible, manage the collection and treatment of stormwater flows within the City, reduce the incidence of flooding and erosion caused by development, and to reduce the amount of stormwater inflow to the wastewater system.

2. Findings.

The city council finds and declares:

1. 1. that effective stormwater management is a necessary component to maintain a healthy and safe environment for the general public, to reduce flooding and erosion on public and private lands, and to facilitate compliance with environmental laws relating to water quality and water pollution;

1. 2. that reduction of stormwater runoff and flow loads into public storm and sanitary sewer systems is in the public interest and has a positive environmental value. Likewise, reduction of stormwater flows onto the public right-of-way and public lands reduces pollution and contamination from stormwater runoff, and enhances the safe and efficient use of the public right-of-way for public travel and emergency vehicle access and the use of public lands for intended purposes;

1. 3. that it is in the public interest to develop and enforce effective requirements for stormwater management through onsite stormwater facilities. Such a policy develops a solution to stormwater problems at the earliest stage, reduces the public costs of stormwater management, and encourages premises and local areas to participate in responding to stormwater management needs at the initial stages of the problem;

1. 4. that onsite stormwater facilities should be installed and kept in good maintenance, repair, and operational effectiveness as an essential part of a stormwater management program in the public interest;

1. 5. that property development largely replaces natural vegetation and exposed soil with impervious surfaces and lawns. This generates additional stormwater runoff during rainstorms or when snow melts, and similar infiltration associated flooding problems, particularly within the special drainage districts (SDDs). Stormwater collection systems concentrate this flow and infiltration systems move surface runoff down into the ground. Additional runoff resulting from development can increase flows in the natural location of drainage systems or otherwise existing channels, create new flows, increase or cause ponding in low areas, and raise groundwater levels. Flooding of new and existing structures, water over roadways, shallow groundwater, and increased erosion can result from post-development surface runoff and infiltration. A regulatory program to address problems created by these circumstances including the cumulative impact of multiple development is in the public interest;

1. 6. numerous stormwater studies identifying the impacts identified above have been completed or are currently being developed. These studies include site specific analysis of developments within the two identified SDDs and also include more generalized studies including but are not limited to:

1. 1. 1. City of Spokane stormwater management plan dated March 2004;

1. 1. 2. model municipal stormwater program for Eastern Washington (draft) and stormwater management manual for Eastern Washington dated September 2005 (Publication Number 04-10-076);

1. 1. 3. geotechnical evaluation, existing residential development by Geo Engineers;

1. 1. 4. staff report to board of county commissioners from public works department, stormwater utility section re North Spokane stormwater planning area dated December 19, 1999;

1. 1. 5. memorandum to Steve Worley, Spokane County, from James Harakas, Garry Squires of Geo Engineers re: seismic refraction report dated November 13, 2000;

1. 1. 6. seismic refraction survey, Five Mile Prairie by Budinger & Associates dated December 22, 2000;

1. 1. 7. memorandum to county commissioners from Brenda Sims and Steve Worley, stormwater section, division of utilities, re: Five Mile Prairie refraction survey report dated January 31, 2001;

1. 1. 8. final report; hydrogeologic services North Spokane stormwater management plan for Spokane County by Geo Engineers dated May 4, 2001;

1. 1. 1. geology, groundwater conditions and suitability of shallow groundwater for stormwater infiltration, Glenrose and Central Park watersheds, prepared for Montgomery Watson and Spokane County, Woodward-Clyde (preliminary – subject to change) dated December 9, 1997;

1. 1. 10. feasibility study: Moran Prairie groundwater collection/disposal option prepared for City of Spokane by URS Greiner Woodward Clyde (draft report) dated March 1, 1999;

1. 1. 11. guidelines for stormwater management, Spokane County public works division of engineering and roads. Includes addenda through August 2003; and

1. 1. 12. infiltration rate and soil classification correlation, Spokane County, Washington by Geo Engineers, Budinger & Associates, and Cummings Geotechnology, Inc., dated February 18, 2004.

The above studies are on file with the director.

Date Passed: Monday, March 8, 2010

Effective Date: Sunday, April 11, 2010

ORD C34564 Section 1