2012 SWMM City of Tacoma Chapter 2 Watershed Designations This chapter identifies and describes the water resource inventory areas (WRIAs), watersheds, basins and sub-basins within the City of Tacoma, and the requirements that are specific to each. Where requirements have been developed for a particular geographic area, these requirements shall be in addition to the Minimum Requirements found in Chapter 3 of this volume unless the text in this chapter specifically indicates that the area-specific requirement supersedes or replaces a Minimum Requirement. Water Resource Inventory Areas (WRIAs) and watersheds are defined as follows: • WRIAs – These are large watersheds based on geographic areas usually associated with large river systems. There are 62 of them which have been identified throughout the state by the Department of Ecology. Portions of two WRIAs are located in Tacoma. They are the Puyallup WRIA (#10) and the Chambers-Clover WRIA (#12). • Watersheds – Nine smaller watersheds have been identified in Tacoma. Some of these watersheds are associated with stream systems and some of them are identified geographically. Many of these watersheds cross political boundaries and are shared by one or more of the municipalities surrounding Tacoma. Information in this document will refer to Tacoma’s nine watersheds and not to the WRIA’s. Information on the WRIA’s can be found at http://www.ecy.wa.gov/apps/watersheds/wriapages 2.1 City of Tacoma Watersheds The information in this manual covers the following nine watershed areas (see Figure 1 - 1). • Flett Creek •Leach Creek • Northeast Tacoma • Joe’s Creek • North Tacoma • Thea Foss Waterway • Tideflats • Lower Puyallup • Western Slopes Volume 1 1- 4 Chapter 2 City of Tacoma 2012 SWMM Figure 1 - 1. City of Tacoma Watersheds Chapter 2 1- 5 Volume 1 2012 SWMM City of Tacoma The City shares watersheds with both Pierce and King Counties, and with various municipalities within these counties. With regard to terminology for smaller areas within a watershed, the term “basin” correlates to an area draining to a particular outfall. A “sub-basin” is a portion of a basin and is defined by a change in land use or is geographically separated from the rest of the basin by branching of the stormwater infrastructure, or piping system. 2.2 Land Use One of the factors determining the need for, and type of, area-specific controls, is the existing level of development and the types of land uses within a particular basin. Within the City of Tacoma, a majority of the available land has been subjected to some level of development and may be subject to land use requirements in addition to the requirements of this manual. All areas experiencing development create increased amounts of impervious surface. 2.2.1 Land Use Regulations In accordance with the Growth Management Act, the City has developed a comprehensive planning effort which includes the adoption of comprehensive land use plans and consistent regulations for implementation. Regulations adopted consistent with the Growth Management Act and Shoreline Management Act, as well as zoning, influence what development and redevelopment will be allowed in specific areas. Zoning regulations limit land use types and densities. Growth Management Act regulations include land use designations and protections such as wetlands and other critical areas, groundwater protection areas, and other resource lands. The City’s Building Code also prescribes parameters that affect: the design of new development and redevelopment; what offsite improvements may be permitted; and excavation, grading, and erosion and sediment control requirements for a given site. Tacoma’s Building and Land Use Services Department maintains a City Generalized Land Use Map, and other resources from which these designations and regulations can be obtained. 2.2.2 Land Use Plans The comprehensive plans developed under GMA address, at a minimum, land use, transportation, housing, capital facilities and utilities. Tacoma has developed a Capital Facilities Program to address utilities and their relationship to the adequate provision of services for existing and future land uses. These documents focus on the provision of adequate utilities, including storm drainage, provided City-wide and within the City’s Urban Growth Boundaries. The Capital Facilities Program demonstrates how the stormwater projects to be developed over the next six years provide the required amount of capacity at the adopted level of service standard to meet the needs of the existing population and projected growth. The City also has developed an Environmental Policy Element as part of its comprehensive planning process. In addition to generalized goals to provide an aesthetic and healthful environment and to ensure conservation, protection, enhancement and proper management of natural resources, this Element specifies a number of more specific policies with respect to natural features of the environment, growth and development, pollution, recreation and open space, energy, land use, air quality, water quality, scenic areas, solid waste recycling and environmental remediation, stormwater runoff, and low impact development. In addition, the Element includes specific policies related to each of the various critical areas, including wetlands and stream corridors, fish and wildlife habitat conservation areas, aquifer recharge areas, flood hazard areas, erosion hazard areas, landslide hazard areas, seismic hazard areas and mineral resource lands. Volume 1 1- 6 Chapter 2 City of Tacoma 2012 SWMM 2.3 Impaired Water Bodies Section 305(b) of the Federal Clean Water Act (CWA) requires Ecology to prepare a report every two years on the status of the overall condition of the state’s waters. Section 303(d) of the CWA requires Ecology to prepare a list every two years containing water bodies not expected to meet state surface water quality standards after implementation of technology-based controls. The State is then required to complete a Total Maximum Daily Load (TMDL) for all waters on that list. The existing list and other related information is available on Ecology’s water quality website: http://www.ecy.wa.gov/programs/wq/links/wq_assessments.html If a project site discharges to one of these listed waterbodies, additional treatment or flow control requirements may apply. 2.4 Floodplains Floodplains are not regulated through the Stormwater Management Manual. However, surface water facilities proposed within flood plains will be reviewed on a case-by-case basis to determine if the facilities are acceptable. Additional analysis and requirements may be needed for surface water facilities located within flood plains. 2.5 Tacoma’s Watersheds and Other Basins – Summary Descriptions 2.5.1 Flett Creek This watershed is 7,153 acres and is the second largest watershed in the City. The area is predominately residential with commercial and light industrial uses in localized areas. The watershed is bordered by Foss Watershed on the east, Leach Creek Watershed on the west and Pierce County to the south. This watershed includes Snake Lake, Wapato Lake, portions of Interstate 5, the South Tacoma Groundwater Protection District and the former South Tacoma Channel Superfund Site. A portion of the Tacoma Landfill Superfund site is also included in this watershed. For information regarding the Landfill Superfund site, see the description under Leach Creek Watershed below. The east side of the watershed flows through a series of holding ponds known as the Hosmer system, prior to reaching the Flett Creek holding ponds. The Hosmer system consists of the Hosmer holding basin (near South 84th Street on the east side of 1-5); Ward’s Lake (directly across I-5 from Hosmer); and the “Gravel Pit” holding basin (just north of Ward’s Lake). In addition to Tacoma’s flow contributions, approximately 800 acres of Pierce County flows into the Hosmer Holding Basin. A small tributary area of Lakewood flows into Ward’s Lake, and WSDOT has a direct discharge to Ward’s Lake. Wapato Lake is also located in the east side of the watershed; however it is not considered part of the Hosmer system. The 900 acre tributary area discharges into the north cell of Wapato Lake and is then piped from the north cell around the main lake to Ward’s Lake. Typical storm events are bypassed in this manner, although during intense rain events stormwater overflows from the north cell into the main lake. The west side of the watershed flows directly into the Flett Creek holding ponds and does not go through the Hosmer system. Chapter 2 1- 7 Volume 1 2012 SWMM City of Tacoma The entire Flett Creek Basin drains through the four Flett Creek holding ponds (located in the vicinity of South 85th and Tyler Streets) prior to discharge to the Flett wetland and creek. A pump station located at the last Flett Creek holding pond pumps stormwater to the Flett Dairy wetlands from which it drains into Flett Creek. Flett Creek is approximately 3.0 miles long and is located in the City of Lakewood. The historic headwaters of the creek were located at least partially in Tacoma but were ditched and/or piped long ago. The lower portion of the creek in the City of Lakewood provides for salmonid spawning. Flett Creek flows into Chambers Creek, which is also a salmonid bearing stream, which discharges to the Narrows Passage. There are two salmon hatcheries on Chambers Creek 2.5.1.1 Wapato Lake Wapato Lake is a 30-acre urban lake and is the central feature of Wapato Park. This park is an 80-acre facility owned by Metro Parks Tacoma. The surrounding land uses are predominantly residential but include commercial uses and portions of Interstate 5. Its valued uses have included recreation (fishing and swimming), wildlife habitat and flood control. Historically, aquatic weed growth, algae blooms, siltation, waterfowl related “swimmers’ itch” and other problems have limited the recreational enjoyment of the lake.