Auburn Stormwater Management Action Planning (SMAP)
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Proposed Stormwater Management Actions
Through the basin prioritization process described below, the review of public comments, and additional evaluation by the City, Olson Creek 1 has been selected as the SMAP priority catchment. Next, the Stormwater Management Action Plan for Olson Creek 1 basin will review and select potential stormwater management actions (SMAs) to implement. The SMAP is available for review at the following link: SMAP Final Report. The possible stormwater actions are described in the table below. The actions are divided into three categories: stormwater facility retrofits, land management/development strategies, and tailored stormwater management program, which are further described below.
To learn more about the SMAP process and the data used in the prioritization process, jump to the SMAP process, geographic data, and equity data sections of the website.
Stormwater Management Actions (SMAs)
Below further describes the three categories used for the proposed stormwater management actions listed above.
Stormwater Facility Retrofits
Retrofits are projects that add new stormwater management (pollutant-removal and/or control of runoff volume) in areas that were developed long ago without any stormwater facilities or with facilities that have since become out-of-date. These retrofits can range from an underground concrete treatment vault to raingardens. Below is an example of one kind of retrofit the City may install.
StormFilter ("Sacramento International Airport Remain Overnight [RON] Apron", from Contech Engineering Solutions)
Land Management/Development
Land management actions are designed to improve or protect streams and other natural waters by addressing the way the City regulates new development and management of already built-out areas.
Examples of land management actions are:
- Growth management: Coordinating with other City departments to update comprehensive plans across the City in ways that include long-range stormwater management and pollution-reducing strategies.
- Developer incentives: Instituting incentives for developers to encourage designs that minimize impacts to natural waters.
- Codes: Reviewing the existing City ordinances and codes for potential updates to development requirements or fee collections that help prevent pollution-generation and help fund the cleanup of historically untreated areas.
- City policies: Update city policies, for example, the way the City tracks and credits tree planting, especially considering the types and height of the trees and how many are planted in groups.
- City programs: Create new programs, such as one to review and track lands within the city that might need additional protection or could be candidates for restoration grants
Tailored Stormwater Management Program
The City already has a program for managing stormwater that includes specific elements required by the State Stormwater Permit. The SMAP process involves enhancing one or more parts of the City’s existing program. This means targeting, prioritizing, customizing, or increasing the frequency of one or more of the following:
- Source Control inspections at institutional, commercial and industrial sites (source control involves inspections to identify pollutant sources and provide education, technical assistance, and enforcement to prevent pollution from these sites)
- City Stormwater Facility Inspections
- City Stormwater System Maintenance
- Public Education and Outreach
- Illicit Discharge Detection and Elimination (IDDE) Field Screening (identifying non-stormwater sources that might be discharging to the storm drain system either accidentally or illegally)
Why is Auburn going through this Stormwater Management Action Planning (SMAP) process?
As part of the Clean Water Act National Pollutant Discharge Elimination System (NPDES), the Washington State Department of Ecology requires the City to implement the SMAP process as outlined in the Western Washington Phase II Municipal Stormwater Permit. More information on the Stormwater Permit can be found at this link to Ecology’s website . The goal of the SMAP process is to achieve water quantity and quality improvements in a specific water body by prioritizing actions on the land that drains to it.
What is urban runoff (stormwater) and why is it a problem?
Rainwater runoff from urban areas – also known as stormwater – is a leading pollution threat to natural waters like lakes, rivers, streams and marine water bodies in Washington State. Pollution in natural waters is harmful to fish and animals, people who swim and play near the water, and the economy of industries that rely on clean water bodies.
Runoff contamination comes from common land uses like vehicular traffic areas, landscaping with fertilizer and pesticides, building materials, spills from activities conducted outdoors, and illicit wastewater connections to the drainage system. Polluted runoff can carry metals, nutrients, pesticides, and harmful organic compounds to natural waters if left untreated.
How will the SMAP benefit our community?
- Improve water quality in water bodies
- Help reduce flood risk
- Protect aquatic habitat and environmental resources
- Create potential opportunities for new open spaces, parks, and trees
- Reflect the community’s values on water quality and inform how and where future actions are implemented
What is coming in the SMAP process?
The SMAP was developed by your stormwater management team at the City using the process shown in the infographic below.
Implementation of the proposed stormwater management actions, including retrofit projects, land management/development strategies, and tailored stormwater management programs.
Geographic Data
Scroll through the series of maps below to learn about what spatial data is used in the SMAP process. These maps are interactive, please feel free to click, zoom, and interact with each map.
Receiving Water Basins
These are also known as watersheds, drainage basins, catchments, subbasins, or subcatchments. A basin is a geographic area where the rain that falls on the land runs off and flows to a common location — known as an outlet or outfall — and discharges into a receiving water body such as a stream, river, lake, or marine water like the Puget Sound. These receiving water basins were delineated based on topography and the municipal storm system (ditches, pipes, etc.) and are the starting point for the SMAP receiving water analysis. They will be sub-divided into smaller subcatchments as part of the SMAP analysis so the City can make even more detailed decisions and prioritizations.
Drainage Catchments
The receiving water basins have been divided into smaller catchment areas based on topography and the City drainage network, as shown on the right. These smaller catchments are at the scale directed by the Permit SMAP requirements and help to focus City decisions for actions to improve water quality. The catchment areas vary, but on average are approximately 1 square mile (640 acres). Click on a catchment area on the map to see the catchment and associated drainage basin names.
Priority Catchments
The assessment of receiving water conditions and other local and regional information generated a list of potential high priority catchment areas, which are shown at the right. Olson Creek 1 (OC1) was chosen as the priority catchment and is the candidate for the first round of focused stormwater management actions. The actions may include stormwater facility retrofits, land management strategies, and enhanced maintenance. Potential actions and proposed project locations will be identified in the next phase of the SMAP process.
Water Quality
Water quality for the City’s receiving waters has been assessed using data from several sources. The City of Auburn has been tracking water quality and flow problems in mapping and categorizing the issues as hydrology, water flow, or water quality. Ecology’s Water Quality Assessment 303(d) List shows receiving waters where state water quality standards have been violated for one or more pollutants based on samples of water or sediment. Stream biologic health is measured based on the richness of macroinvertebrates (organisms large enough to see without a microscope, like crustaceans, mollusks, or aquatic insects) in a water body.
Land Cover
Land cover has an important impact on the rainfall that lands on it, flows across it, and runs off into the natural receiving waters. Hard surfaces, like roadways, sidewalks, compacted gravel, and rooftops allow little or no stormwater to infiltrate into the ground. Vegetated areas like forests, grass, and landscaping meaning they allow air and water to move through into underlying layers. All land covers are classified as either pollution-generating (for example, roads that have vehicular pollutants or farms or playfields that may have fertilizer or pesticides) or non-pollution generating (for example, sidewalks or naturally managed farms and landscapes). Hard surfaces increase rainfall-runoff volumes and frequency, which can erode stream banks, damage habitat, and cause local flooding. Pollution-generating surfaces damage the chemical quality of the rainfall-runoff that reaches the natural water bodies, including groundwater.
Buildable Lands Inventory
City buildable and vacant lands data is tracked as part of the Growth Management Act (GMA) Buildable Lands Statute of 2017. This data will be used in the SMAP process to forecast areas of projected or targeted growth and associated stormwater management upgrades, score and rank sub-catchments, and evaluate impacts to the watershed. Vacant lands are typically not developed at all or have only minor accessory structures. Redevelopable lands have some development, but could include parcels that could be converted to a more intensive use type or parcels that are large enough to be subdivided to create more lots. Planned development lands have already existing development. The parcels shown are for planning purposes only and they may not be developed or redeveloped in the future.
Equity Data
Environmental and socioeconomic stressors, which may contribute to ongoing health inequalities, are being considered in the SMAP process. U.S. Census, U.S. Environmental Protection Agency (EPA), and City data were used to create an equity screening tool that includes a Demographic Index, an Environmental Hazards Index, and an Environmental Opportunity Index. The Combined Equity Index, intended to serve as a general check for extreme scenarios or other patterns, is an average of the other three. The Combined Equity Index is meant to be reviewed along with the other three, not in their place. As the SMAP process continues into prioritization, the analysis will be refined and will show more specific results for geographic areas across the city. Each equity index will be reviewed as part of the ranking and screening in order to select a priority basin.
