Volume III Port Gardner Bay Watershed Plan
Chapter 7 Phillips Creek Basin Plan
Chapter 7—Phillips Creek Basin Plan
7.1 Basin Characteristics
The characteristics of the Phillips Creek basin in terms of water flow, water quality, and habitat together with identified issues are described in this section. The characterization work in part made use of previously prepared documents, data, and reports which are listed in Appendix 1.
A. General Characteristics
Physical Characteristics: Phillips Creek is a small stream system in the Puget Lowlands, running in a roughly south-north direction and discharging into Port Gardner Bay in the Puget Sound. It travels through a 0.13 square mile drainage basin along a total stream length of approximately 1.4 miles. The basin is shown in Figure 7-1. Phillips Creek has a lower main stem segment that extends up from the Burlington Northern Santa Fe Railway (BNSF) culvert for approximately 1,000 feet, at which point the West Fork Tributary diverges from the main stem and continues until 49th Place SW. The main stem continues upstream and stops north of Merrill Creek Parkway near the Millington at Merrill Creek apartment complex. Portions of the system are undeveloped forested area and the remaining area is residential. A majority of the creek flows through an open channel system through a forested ravine with sections of pipe at road crossings.
The headwaters of the basin reach a maximum elevation of 420 feet and ground elevation at the downstream end of the BNSF culvert is approximately 7 feet. The maximum relief of the basin (defined as the difference between the maximum and minimum basin elevations) is 414 feet. Dividing the maximum relief by the length of the basin along Phillips Creek main channel (roughly 5,930 feet), makes the overall basin gradient approximately 7 percent; however, this gradient is considerably greater as the creek descends the marine bluff to Port Gardner Bay.
Topography throughout the basin is steep and all of the developed area is residential. Existing land cover within the basin is shown in Figure 7-2. Riparian habitat in Phillips Creek system is along the banks of the system. Stream habitat, where the system is daylighted, is moderately impacted by land use activities and drainage modifications.
Phillips Creek descends through a steep, forested ravine from its upper basin into its lower basin and down the marine bluff that faces Port Gardner Bay. The valley walls are extremely steep in this ravine with side slopes ranging between 25 and 45 percent throughout the stream channel. The Phillips Creek basin is largely forested, and the steep slopes of the ravine have precluded the encroachment of development as seen throughout the basin along the creek channel. Complete fish passage barriers exist as the system descends the marine bluff, with gradients in excess of 20 percent and cascades and water drops of 6 feet or greater in height. High levels of fine sediments in the lower portion of the Phillips Creek system have also been identified as habitat impairments.
Woody debris and fine sediment are supplied to the channel in periodic pulses from failures along the valley wall; introduction of sediment into the stream from valley wall failures appears to cause localized reductions in stream bed slope. Channel segments upstream from road crossings may also have lower stream bed slopes as a result of lower sediment conveyance capacity and aggradation of sediment in the vicinity of the upstream culverts.
Soils: Soils in the Phillips Creek basin are mostly gravelly sandy loams derived from glacial parent materials. The dominant soil types for hydrologic modeling in the Phillips Creek basin
City of Everett Surface Water Comprehensive Plan 7 - 1 Volume III—Port Gardner Bay Watershed Plan November 2017 Chapter 7—Phillips Creek Basin Plan include till and outwash. The distribution of these soil types within the Phillips Creek basin are shown in Figure 7-3. Till soils are from the Alderwood soil series and outwash soils are from the Everett soil series.
Existing Land Use: Land use in the Phillips Creek basin under existing conditions is all residential. The north part of the basin is zoned as suburban residential. The southern portion of the basin from Merrill Creek Parkway to approximately the 5100 block is zoned as multi-family, medium density. The total effective impervious area (impervious areas draining to a conveyance system via sheet flow or discrete conveyance) for the basin is approximately 28 percent (21.6 acres), with 35 percent (27.8 acres) of the basin covered with lawns, and 37 percent (29.0 acres) covered with trees. This estimate was based on aerial photography from 2011.
Future Land Use: The future land use (ultimate build out) was based on a process that determined the residential parcels that could be developed in the basin and then calculated a percent impervious based on the 2009 City of Everett Growth Management Comprehensive Plan Land Use Maps. Another process was used to calculate increase in imperviousness from short plat developments of small parcels to get a worst case buildout scenario. All other parcels with other designations remained the same as existing land use. In general, the percent of land that is impervious increased within the Phillips Creek basin under future conditions.
B. Water Flow Characteristics
The key water flow characteristics for the basin are defined by the hydrologic and hydraulic processes at work in the basin, peak and seasonal flow rates, and the existing stormwater infrastructure within the basin.
Hydrologic and Hydraulic Processes—Upland Processes Potential Evapotranspiration Evaporation is a major factor in the hydrologic cycle. The Phillips Creek basin receives approximately 40 inches of precipitation each year. Of these 40 inches, approximately half returns to the atmosphere as evaporation or transpiration (Snohomish County North Creek Drainage Needs Report [DNR] No. 10, 2002). Most precipitation intercepted by vegetation transpires, and is accounted for as evaporation. The amount of water lost to evaporation versus transpiration is nearly impossible to distinguish, so they are usually grouped together as potential evapotranspiration (PET) in the HSPF model.
Infiltration/Soil Moisture Capacity The type of soil within the basin drives the amount of precipitation that can infiltrate and what happens to the infiltrated water. Infiltrated water can be stored, lost to deep infiltration, or delivered to a stream as shallow groundwater.
Within the lower ravine portion of Phillips Creek, groundwater is expressed at the geologic formation interface between the Esperance Formation and Whidbey Formation layers. The Esperance Formation is an advance outwash and is highly permeable while the Whidbey Formation is a nearly impermeable till soil and lies below the Esperance Formation. Till soils associated with the Whidbey Formation interglacial unit contain some clay and is associated with a number of large deep-seated landslides.
7 - 2 City of Everett Surface Water Comprehensive Plan Volume III—Port Gardner Bay Watershed Plan November 2017 SURFACE WATER COMPREHENSIVE PLAN FIGURE 7-1 PHILLIPS CREEK BASIN MAP O u nd LY n S o M o P si I s R C se D B s F LV o CITY OF EVERETTIF D L P C AVE 2014 NA RO AD M BLVD EO ILT K U R I M D G W E M O NT
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Disclaimer: The information shown in this map is assembled GIS data created and³ acquired by Otak Inc., City of Everett, and from Snohomish County GIS. This data is not to survey accuracy and is meant for planning purposes only.
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7 - 4 City of Everett Surface Water Comprehensive Plan Volume III—Port Gardner Bay Watershed Plan November 2017 SURFACE WATER COMPREHENSIVE PLAN FIGURE 7-2 PHILLIPS CREEK
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7 - 6 City of Everett Surface Water Comprehensive Plan Volume III—Port Gardner Bay Watershed Plan November 2017 SURFACE WATER COMPREHENSIVE PLAN FIGURE 7-3 PHILLIPS CREEK
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7 - 8 City of Everett Surface Water Comprehensive Plan Volume III—Port Gardner Bay Watershed Plan November 2017 Chapter 7—Phillips Creek Basin Plan
The Phillips Creek basin is 30 percent outwash, 5 percent saturated, and 65 percent till per soils classified by the Natural Resources Conservation Service (NRCS). The till and outwash soil types are used in the hydrologic modeling. Till soils are from the Alderwood soil series and outwash soils are from the Everett soil series. Alderwood soils are well drained at the surface with deficient under-drainage due to an impermeable cemented substratum; and Everett soils are highly permeable with low water capacity (Snohomish County DNR No. 10). Shallow infiltration is likely within Alderwood soils, while deep infiltration occurs in Everett soils. The outwash (Everett) soils are scattered within three pockets throughout the basin with the smallest of the three around W Mukilteo Boulevard. The second area is in the forested area along the creek in the central portion of the basin and the third area is at the south end of the basin under the Millington apartments and the headwaters of the main stem. The remaining soils are all till.
Hydrologic and Hydraulic Processes—Stream Corridor Processes Across Stream Corridor Tributary Flow Phillips Creek begins north of the pond for the Millington apartments and continues north for about 0.8 miles before the confluence with the West Fork Tributary. It then drains another 0.2 miles to Port Gardner Bay. The main stem and West Fork Tributary are shown in Figure 7-1.
Overland Flow Due to the urbanized watershed, precipitation travels as overland flow for only short distances before it is collected in a conveyance system. This leads to faster travel times for water entering the tributaries, less opportunity for infiltration, and only shallow groundwater flow. The overall result is higher volumes and peak rates of runoff compared to a more natural system. The areas where precipitation enters the channel as overland flow are confined to the corridors along the creek and the backyards of the residences on the east side of Harbor Lane, south of 49th Place SW.
Stormwater Inflow The basin’s drainage infrastructure collects and discharges stormwater runoff at three areas throughout the basin, at the headwaters of the main stem, near Belvedere Avenue, and W Mukilteo Boulevard. This enters the creek as stormwater inflow through outfalls and manmade conveyances. There are five mapped outfalls along the main stem where stormwater from developments above the ravine discharges into the creek.
Along Stream Corridor Flow Characteristics Due to urbanization, the main stem of Phillips Creek is expected to experience flows with higher volumes and peak rates and shorter durations as compared to a more natural system. The West Fork Tributary has a very small tributary area consisting of overland flow from pervious areas so it is not expected to experience high volumes for peak rates.
Channel Constrictions/Road Crossing Natural or manmade constrictions in the channel tend to dampen peak flows by storing water and releasing it slowly. In the main stem, there does not appear to be any constrictions in flow, although the 2-foot diameter corrugated metal pipe culvert crossing W Mukilteo Boulevard has a large amount of deposition from several landslides that have occurred upstream. The upstream end of the culvert appears to get dredged periodically in order to keep the culvert from filling up with sediment.
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The crossing at the BNSF railway is an 18-inch concrete pipe that has filled with a couple inches of sediment. There is water seeping through the railroad embankment but does not currently appear to be causing any issues.
Length of Open Flow/Pipe Sections Main Stem: The main stem begins north of the pond for the Millington apartments and drains north approximately 1 mile to Port Gardner Bay. It is an open channel contained within a steep walled ravine with a short piped section through 14th Drive W and a culvert crossing at W Mukilteo Boulevard. The culvert crossing W Mukilteo Boulevard is approximately 218 feet long with a section of 24-inch diameter pipe followed by a 30-inch diameter pipe.
West Fork Tributary: The West Fork Tributary originates in an open channel between the residences north of 49th Place SW and is piped under Belvedere Avenue across private property to its confluence with the main stem.
Water Surface Slopes According to the City’s GIS data, the main stem of Phillips Creek has an average slope of approximately 8 percent and the average slope of the West Fork Tributary is 17 percent. Water surface slopes follow the ground surface slope under low flows. As flows increase during storm events, backwater behind natural and human made constrictions flatten the water surface slopes.
C. Basin Runoff Characteristics
Peak Flows A hydrologic model (uncalibrated) of Phillips Creek was developed as part of this basin plan and is described in Section 7.2. This model was used to determine flows at various locations along Phillips Creek. The model used 28 percent effective impervious area for existing land use. The modeled existing peak flows based on existing land use and historic precipitation record are presented in Table 7-1.
Table 7-1 Existing Peak Flows Based on Current Land Use and Precipitation (CFS) 10- 50- 100- Sub- 2-year 5-year 25-year Location2 year year year basin (FF)1 (FF)1 (FF)1 (FF)1 (FF)1 (FF)1 PH-1 Main stem at Outfall 10.5 14.8 17.9 22.1 25.4 28.9 1FF: Flood Frequency return interval 2Peak Flows are recorded for the location at which runoff discharges from the subbasin
The expectation is that the current flows in the creek will be higher based on a future increase in impervious area in the basin. Results of the hydrologic modeling are provided in Section 7.2.
Seasonal Flows The flow regime in the Phillips Creek system is designated by Snohomish County as seasonal in the lower portion of the system and unknown but presumably seasonal in the upper portion of the system. The City of Everett designates the system as perennially flowing in the lower reaches and showing seasonal flow in the upper reaches. Seasonally flowing portions of the system are maintained by direct stormwater runoff and shallow groundwater from the till soils during the fall, spring, and winter; and are expected to go dry in the summer.
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The hydrologic analysis developed average seasonal flows for the Phillips Creek basin. These flows are important when looking at the habitat capabilities of the system relative to the changes in flow rate between the seasons. Flows are presented below, in Table 7-2, for existing land use with historic precipitation, as well as, future land use with precipitation revisions for possible climate change (worst case).
Table 7-2 Average Seasonal Flows at the Outfall (CFS) Existing Land Use with Future Land Use with Climate Season Historical Precipitation Change Precipitation Fall (Oct., Nov., Dec.) 0.26 0.33 Winter (Jan., Feb., Mar.) 0.30 0.36 Spring (Apr., May, June) 0.16 0.20 Summer (July, Aug., Sept.) 0.06 0.08
D. Stormwater Infrastructure
The majority of the public stormwater infrastructure is included in the City’s GIS database. This includes pipes, manholes, catch basins, culverts, ditches, outfalls, and detention or infiltration facilities. There is only one stormwater facility, located in the Millington apartments at the south end of the basin. It collects runoff from the entire complex before discharging to the headwaters of Phillips Creek.
Identified Issues Reported water flow issues are most often related to a surface water condition, where peak flow rates exceed the normal capacity of the existing conveyance system and flows in an uncontrolled manner causing nuisance issues.
The process for identifying water flow issues involved reviewing available existing reports, GIS information, and drainage complaints from the City’s database; conducting windshield field assessments; meeting with City staff from the Surface Water Division and the Maintenance Division; and performing hydrologic and hydraulic analysis.
After completing this process, it was determined that there are no water flow issues in the Phillips Creek basin.
E. Water Quality Characteristics
Puget Sound is recognized as an estuary of national significance under the National Estuary Program established in the 1987 amendments of the Clean Water Act. Washington State established the Puget Sound Initiative to protect and restore Puget Sound. In response to the Puget Sound Initiative, the Washington State Department of Ecology (Ecology) has identified Port Gardner Bay as a priority bay for cleanup and restoration.
Waterbody and Watershed Conditions—Designated Uses and Criteria Washington State has developed criteria for the protection of surface waters of the state. These criteria are set forth in Washington Administrative Code (WAC) Chapter 173-201A Water Quality Standards for Surface Waters of the State of Washington, and are shown in Table 7-3. In addition, Phillips Creek must meet the toxics criteria for metals and other toxic substances. Uses
City of Everett Surface Water Comprehensive Plan 7 - 11 Volume III—Port Gardner Bay Watershed Plan November 2017 Chapter 7—Phillips Creek Basin Plan for the waterbody have been designated, regardless of whether or not the uses are currently attained, and criteria were established. Phillips Creek does not have specific designated uses, therefore the designated uses for all surface water applies. The assigned designated uses apply regardless of whether or not the uses are currently attained. These designated uses include: • Salmonid spawning, rearing, and migration • Primary contact recreation • Domestic, industrial, and agricultural water supply1 • Stock watering1,2 • Wildlife habitat • Harvesting • Commerce and navigation1,2 • Boating1,2 • Aesthetic values 1Designated uses within the City that are not currently attained. 2Some of these designated uses are not attainable within this waterbody, and are not expected to be attainable—and may not be desirable—based on the waterbody characteristics.
Table 7-3 Phillips Creek Water Quality Criteria (WAC 173-201A) for Dissolved Oxygen, Temperature, Turbidity, pH, and Bacteria Use Category Parameter Criteria 8.0 mg/L Dissolved Oxygen Lowest one-day minimum 17.5 °C (63.5°F) Temperature Highest seven-day maximum Salmonid Spawning, Shall not exceed: Rearing, and • 5 NTU1 over background when the background is 50 Migration Turbidity NTU or less; or • A 10 percent increase in the turbidity when the background turbidity is more than 50 NTU pH2 shall be within the range of 6.5 to 8.5, with a human pH caused variation within the range of less than 0.5 units Fecal Coliform organism levels must not exceed a geometric mean value of 100 colonies/100 mL, with not Primary Contact Bacteria more than 10 percent of all samples (or any single Recreation (Fecal Coliform) sample when less than 10 sample points exist) obtained for calculating the geometric mean value exceeding 200 colonies/100mL 1NTU—unit of measurement for turbidity; Nephelometric Turbidity Units 2pH Units—measurement of pH is expressed as the negative logarithm of the hydrogen ion concentration
Water Quality Assessment for Washington State Section 303(b) of the Clean Water Act requires Washington State to prepare a list of all waters in the state for which designated uses are impaired by pollutants. These are water quality limited waterbodies that do not meet surface water quality standards, and are not expected to improve within the next two years. In addition, Section 305(b) of the Clean Water Act requires an assessment of the status of all the state’s waters. Ecology has combined these requirements in the Water Quality Assessment; Category 5 of the Assessment is the 303(d) impaired waterbodies. Phillips Creek is not listed in the Water Quality Assessment for Washington State.
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Watershed-Related Reports There are no water quality reports for Phillips Creek.
Pollutant Sources Pollutant sources are generally referred to as either point sources or nonpoint sources. Point sources are discharges of pollutants from a point source, such as pipes, outfalls, and conveyance channels. Nonpoint source pollution typically comes from diffuse sources.
Point Sources The 1972 Federal Water Pollution Control Act amendments require that all industrial, wastewater, and municipal point source dischargers of pollutants obtain a National Pollutant Discharge Elimination System permit (NPDES). Historically, this permit was issued to industrial and wastewater treatment facilities. The 1987 Clean Water Act amendments expanded the permitting system to include industrial and municipal stormwater discharges.
Ecology has been delegated the authority to administer the NPDES permitting program by the Environmental Protection Agency (EPA). Ecology issues several categories of general NPDES Permits, including: • Construction General Permit • Wastewater Treatment General Permit • Industrial Stormwater General Permit • Phase II Municipal Stormwater General Permit
Construction General Permit The City of Everett holds a Construction General Permit to control sources of sediments and pollutants from constructions sites. This permit is currently employed at several large construction projects in the basin.
Wastewater Treatment General Permit The City’s Wastewater Treatment General Permit contains appropriate pretreatment standards and requirements for wastewater discharge in the City’s publicly owned sewage treatment system.
Industrial Stormwater General Permit There are no Industrial Stormwater General Permit issued in Phillips Creek.
Phase II Municipal Stormwater General Permit The City of Everett holds a Phase II Municipal Stormwater Permit. This permit allows the City to discharge stormwater from their Municipal Separate Storm Sewer System (MS4) to surface and groundwater.
Nonpoint Sources The term "nonpoint source" is defined to mean any source of water pollution that does not meet the legal definition of "point source" in section 502(14) of the Clean Water Act. That definition states: The term "point source" means any discernible, confined and discrete conveyance, including but not limited to any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, or vessel or other floating craft, from which pollutants are or may be discharged. This term does not include agricultural storm water discharges and return flows from irrigated agriculture.
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Unlike pollution from industrial and sewage treatment plants, nonpoint source (NPS) pollution comes from many diffuse sources. NPS pollution is caused by stormwater moving over the ground. As the stormwater runoff moves, it transports natural and human-made pollutants into receiving waterbodies.
Urban Sources Urban watersheds have many types of impervious surfaces, including buildings, sidewalks, roads, driveways, and parking lots. Sediment and other pollutants could accumulate on these surfaces between storm events, and may be washed off into storm drains or directly into streams during storms. Thus, surface water runoff becomes a method by which pollutants may be are transported to Phillips Creek. Urban development may expose the area to a wide variety of chemical substances from commercial, residential, and industrial activities. Pollutant types may become more complex and variable with increasing urbanization. Typical pollutants found in surface water runoff in urbanized watersheds include sediment, nutrients, pathogens, metals, petroleum products, and organics. The fecal coliform in areas that have sewers is most often from animals like beavers, raccoons, dogs, rats, and birds.
Phillips Creek receives stormwater from residential neighborhoods. Most of these neighborhoods were developed prior to the requirement to provide stormwater treatment, and therefore untreated stormwater may be discharged to Phillips Creek. Pollutants associated with residential activities include metals and hydrocarbons from vehicle use and maintenance, bacteria and nutrients from pet waste, soaps and toxics from vehicle washing, nutrients and toxics from fertilizers and pesticides, and sediment from erosion.
Road systems covered under municipal NPDES permits have conditions such as street sweeping, catch basin cleaning, ditch maintenance, and pond maintenance for road system treatment that are all part of a city-wide pollutant management program.
Wildlife Sources Phillips Creek provides habitat for a multitude of wildlife, including beaver, raccoons, opossums, and many species of birds. Wildlife is a source of bacteria and can increase the fecal coliform bacteria levels within Phillips Creek.
Waterbody Monitoring Data—Water Quality Data There is no available water quality data for Phillips Creek.
Macro-invertebrate Data Benthic macro-invertebrates are monitored because they are good indicators of the biological health of stream systems and play a crucial role in the stream ecosystem. An analysis of the macro-invertebrate community structure can be used to determine the ecological health of streams. The Benthic Index of Biotic Integrity (B-IBI) is a standardized scoring system that can be used to compare and rank the health of streams.
Macro-invertebrate samples were not taken in Phillips Creek.
Analysis of Stream Health Based on Data and Pollutant Sources There is no water quality data available for analysis; however it is expected that water quality standards are met during baseflow conditions.
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Conventional Parameters (Physical) Conventional parameters include the physical water characteristics for the support of aquatic organisms, including fish. Temperature, dissolved oxygen, turbidity and pH are expected to meet water quality criteria. The vegetative cover and riparian buffers provide shading to cool the water. Riffles provide oxygenated water in Phillips Creek.
Bacteria Bacteria sources within the basin include animal waste (pet and wildlife). Human waste is not a significant source because onsite sewage treatment (septic tanks) does not appear to be present in the basin according to City data. Currently, human waste is treated at the Everett Water Pollution Control Facility.
Nutrients The overabundance of nutrients can be problematic in stream systems and receiving waters. In slow moving streams and lakes, phosphorus is typically the limiting nutrient for plant production. In marine waters, the limiting nutrient is often nitrogen. When these limiting nutrients are present, plant production can be stimulated. An overproduction of plants and algae can alter the pH and reduce oxygen during decomposition.
There is no indication of a nutrient issue in Phillips Creek.
Metals The toxicity of metals on aquatic organisms depends on the form the metal takes and the availability of the metal to be toxic (bioavailability). The metal toxicity criteria are based on the dissolved fraction of the metal and the hardness of the water. Hardness of the water is a measure of the mineral content. Rain water is generally very soft, and as the water comes into contact with the soils, minerals are dissolved in the water. Metals are toxic to aquatic organisms at lower concentrations in soft water (low hardness).
There is no indication of metal toxicity in Phillips Creek during baseflow conditions.
F. Summary of Water Quality Characteristics
There is no water quality or macro-invertebrate baseline data for Phillips Creek. However, water quality issues that would be expected include: • Stormwater from landscape, commercial, and road systems may be discharged with limited treatment; • Stormwater from some residential neighborhoods are discharged with limited treatment.
Potential water quality issues are due to high amounts of impervious area, pet waste, dumping in critical areas and limited water quality treatment being provided.
G. Habitat Characteristics
Stream Characteristics, Regulatory Context Stream typing of Phillips Creek was available from three different agencies: The City of Everett, Snohomish County, and Washington State Department of Natural Resources. The reported stream typing is shown in Table 7-4, and presents consistent typing.
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Table 7-4 Phillips Creek Stream Typing Regulatory Reach Location Stream Type Agency City of Everett Main stem – at Puget Sound shoreline Type S – Shoreline of the state City of Everett Main stem – from Puget Sound to upper wetland Non-fish bearing, perennial City of Everett Main stem – upper wetland and above Non-fish bearing, seasonal City of Everett West Fork Tributary Unknown Snohomish County Main stem – all reaches Non-fish habitat, seasonal Snohomish County West Fork Tributary Unknown Washington State Department of Puget Sound shoreline Type F - fish bearing Natural Resources Washington State Department of Upstream of railroad culvert Type N, non-fish bearing Natural Resources
Stream Characteristics, Geomorphic Context Phillips Creek is a high-gradient, steep-walled ravine Puget Lowland stream. The freely flowing portion of the channel has a low sinuosity channel shape and configuration and a basin slope of 8 percent with a maximum relief of 407 feet. Based on the evaluation of one 300-foot long stream reach upstream of the culvert at W Mukilteo Boulevard, the weighted bankfull width and depth are 11.5 feet and 2.1 feet respectively. The channel capacity is often limited by small bank failures and debris accumulations.
Riparian Ecosystems The terrestrial and riparian vegetative community in the Phillips Creek basin consists of a relatively narrow corridor of primarily deciduous forest. Most of the forested habitat corridor is surrounded by residential development. The steep-sided ravine topography of the system has limited the encroachment of development somewhat, although residential structures and lawns occur in relatively close proximity to the stream system and its riparian habitat in many areas.
Aquatic Ecosystems Aquatic habitat in Phillips Creek was assessed along the main stem of the system upstream of W Mukilteo Boulevard using the field stream habitat survey methodology described below. A number of habitat parameters are important for fish and other aquatic biota, and may be assessed as physical components that support the biological functions of stream systems. Such parameters include stream substrate composition and embeddedness, large wood, pool frequency, fisheries resources, fish barriers, wetlands, and riparian vegetation and fauna. These parameters are assessed below, based on the stream habitat survey results and other available data.
Aquatic Ecosystem Results Overall Condition Similar to other drainages within the City of Everett, aquatic habitat in the Phillips Creek system has been impacted by historic and ongoing land use patterns. Although loss of forested habitat, development, and conversion of land to impervious surfaces has narrowed the riparian vegetative corridor for the system, the steep-sided ravine terrain has somewhat limited the loss of riparian habitat in Phillips Creek. The presence of a mixed deciduous forest along the ravine slopes and
7 - 16 City of Everett Surface Water Comprehensive Plan Volume III—Port Gardner Bay Watershed Plan November 2017 Chapter 7—Phillips Creek Basin Plan floor results in a limited supply of large wood, although much of the large wood is slightly small and does not necessarily provide the full suite of habitat functions of larger wood units. Riparian wetlands and slope wetland habitat associated with groundwater expression from the ravine walls further increases habitat complexity and function in the lower Phillips Creek system.
The forested riparian and upland terrestrial habitat shows some vertical complexity, with a shrub understory and herbaceous layer underlying the canopy throughout the surveyed reach. Shading of the lower Phillips Creek system appears adequate, providing thermal buffering of the stream from warmer temperatures during the summer months. Organic input (e.g., leaf litter, terrestrial invertebrates, etc.) to the aquatic system for the riparian and terrestrial habitat adjacent to the aquatic stream corridor appears adequate. Although the stream corridor lies within the larger scale, landscape-level City of Everett urban matrix, the existing riparian and terrestrial corridor adjacent to the Phillips Creek system provides moderate levels of habitat function with regard to shading, large wood, organic input, wildlife habitat and movement corridor, and vertical and horizontal structural habitat complexity.
Fine sediment in the lower Phillips Creek system is abundant and problematic, resulting in often highly embedded gravels in riffle units, and showing a tendency to fill in stream habitat units that might otherwise become pools—decreasing the residual depths in these units and causing them to function as deeper riffles, and resulting in very limited pool habitat in the system. Should resident salmonid fish occur or be introduced into the lower Phillips Creek system, lack of pool habitat would limit flow refugia during the winter, as well as limiting deeper water refugia during the low-flow summer months. In addition, the degree of embeddedness observed in the riffle habitat for the lower system would negatively impact development of salmonid eggs and hatchlings should spawning occur in the system. The delivery of sediment in large quantities (mass wasting) is a natural process occurring on both public and private land. Identifying specific sediment sources was outside the scope of this plan.
Natural and manmade fish barriers are present in the lower Phillips Creek system, and include a perched culvert under the BNSF railroad tracks, natural gradients and cascades that impose complete passage barriers at the marine bluff, and a potential partial barrier under W Mukilteo Boulevard. Anadromous salmonid access does not occur in this system, and would not have occurred historically based on the naturally occurring gradient and cascade barriers.
Substrate Composition and Embeddedness The substrate in the lower Phillips Creek basin is dominated by fine materials, generally consisting of sands. The fine substrate composition and embeddedness are not conducive to salmonid spawning or egg development in riffle habitat, or to pool formation and maintenance within the stream corridor. Some of this fine sediment is being derived from slumping and slope failures of the steep ravine walls but urban sediment input from roadways, other impervious surfaces, and point-source erosional areas may be introduced into the system upstream of the surveyed reach and entrained into the lower reaches, as well.
The National Marine Fisheries Service (NMFS) has developed a tool for assessing aquatic and riparian conditions; this tool is referred to as a Matrix of Pathways and Indicators (NMFS, 1996). The Matrix allows a qualitative assessment of habitat conditions (indicators) to be made; each indicator may be characterized as “properly functioning”, “at risk”, or “not properly functioning” depending upon the measured value of the indicator. Substrate embeddedness is one such indicator, considered important as a habitat metric in salmon spawning riffle habitat and in the suitability of riffle habitat for invertebrates—an important element in the stream food web. The embeddedness indicator is considered “properly functioning” if fine sediment makes up less than
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20 percent of the surface of the riffle substrate, “at risk” if fines make up 20 to 30 percent of the surface of the substrate, and “not properly functioning” if fines make up more than 30 percent of the substrate surface. Most of the riffle habitat in the representative reach surveyed was at risk or not properly functioning due to fine sediment in the substrate.
Information on riffle conditions by stream reach shown in Figure 7-2 are summarized in Table 7-5.
Table 7-5 Riffle Conditions by Habitat Reach Reach No.1 Bed Material Embeddedness Condition2 Reach 1 Fines and gravels High (>75%) Not properly functioning (0+00 to 1+42) Reach 2 Fines and gravels High (>75%) Not properly functioning (1+85 to 3+00) 1See Figure 3-1 for habitat reach locations 2NMFS Matrix of Pathways and Indicators
Large Wood The lower Phillips Creek system shows a moderate occurrence of large wood in the surveyed reach, due to the relatively wide, forested riparian system providing recruitment potential. The large wood in the system is relatively small, ranging from 0.75 feet to 1.75 feet in diameter and a mean length of approximately 16 feet. Large wood appears to be derived from mostly deciduous tree species. Although the amount of large wood in the lower reaches of Phillips Creek would meet the NOAA NMFS Matrix of Pathways and Indicators criterion for amount of large wood, the diameters and lengths of the lower Phillips Creek large wood are somewhat small for providing full habitat and pool formation functions. The calculated large wood density in the surveyed reach is 158 pieces per mile.
Pool Frequency In general, pool frequency and residual pool depths are very low in the lower Phillips Creek system. Almost the entire stream habitat in the surveyed reach was comprised of riffle habitat, with some steeper cascade habitat and little pool habitat. Fine materials, comprised primarily of sands, appear to have filled in depressional areas in the stream bed that would otherwise contain enough residual depth to provide pool habitat. The stream survey indicated that these sand-filled stream habitat units were functioning as deeper riffles rather than pools, and would provide limited flow refugia for fish during the winter, as well as limiting deeper water refugia for fish during the low-flow summer months. The surveyed reach had zero pools and therefore does not meet pool frequency or percentage standards for a stream of this size (average channel width between 10 and 15 feet), and this pool frequency parameter is considered to be not properly functioning per the NMFS Matrix of Pathways and Indicators.
Fishery The Catalog of Washington Streams and Salmon Utilization (Williams et al., 1975) indicates an unknown salmonid usage for Phillips Creek, and Washington Department of Fish and Wildlife (WDFW) SalmonScape (2010) indicates no record of salmonid occurrences in Phillips Creek. Based on stream size, flow regimes, and naturally occurring barriers, fish are unlikely to be present in any of the stream reaches in the system.
Recent fish surveys, conducted by the Tulalip tribe (Beamer et al., 2013), were conducted in an unnamed stream near Darlington Beach that appears to be Phillips Creek. No fish were found in the stream system during the surveys.
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Fish Barriers Natural and manmade fish barriers are present in the lower Phillips Creek system, and include a perched culvert under the BNSF railroad tracks, natural gradients and cascades that impose complete passage barriers at the marine bluff, and a potential partial barrier under Mukilteo Boulevard. Anadromous salmonid access does not occur in this system, and would not have occurred historically based on the naturally occurring gradient and cascade barriers.
Wetlands Most of the wetlands in the lower Phillips Creek drainage area are small riverine wetlands associated with the stream system and with forested, scrub/shrub, and emergent plant community components. Additionally, small seep wetlands with similar plant community components occur further up the ravine walls, their hydrology provided by groundwater expressing along the interfaces between permeable and impermeable soil layers. Forested wetland vegetation was generally dominated by red alder, willow species, black cottonwood, and occasional western red cedar, while the scrub/shrub and emergent communities consisted of salmonberry, stink currant, devil’s club, skunk cabbage, piggyback plant, stinging nettle, horsetail, and creeping buttercup.
Phillips Creek riverine and slope wetlands were observed in association with much of the surveyed stream reach. These wetlands, particularly the riverine ones, appear to provide some water quality functional benefits, as well as water storage benefits. Additionally, the wetlands associated with Phillips Creek are likely to provide habitat functions for invertebrates and vertebrate wildlife, including complexity of vegetation structure and interspersion of habitat, presence of undisturbed buffers of sufficient width, and the nearby presence of habitat features such as snags and logs.
Vegetation and Fauna Species Abundance: Although riparian vegetation diversity and abundance is limited along the upper Phillips Creek drainage corridor, riparian vegetation and fauna appear to be much more diverse and abundant in the lower, surveyed reaches of Phillips Creek. A mixed deciduous- coniferous forested community is the dominant habitat in these reaches, although comprised of a greater proportion of deciduous tree species compared to coniferous ones. Dominant tree species in this habitat consist of red alder, big leaf maple, and black cottonwood. Coniferous species such as western red cedar and western hemlock are found on the ravine floor and walls, while Douglas fir were noted as occurring higher up along the ravine walls. A shrub layer understory and herbaceous layer was present throughout the surveyed reaches, with salmonberry, stink currant, and vine maple occurring as the dominant shrub species and other shrub species such as Indian plum, red huckleberry, red elderberry, and various willow species co-occurring with the dominant shrubs. Herbaceous and lower-growing plants, particularly stinging nettle and piggyback plant, are abundant throughout the Phillips Creek drainage. Other herbaceous species include gallium, herb-Robert, horsetail, lady fern, and bracken fern.
The Phillips Creek reaches within the lower portion of the stream corridor contain riparian habitat consisting of second growth trees and a complex understory as noted above, as well as a mosaic of small wetland patches scattered along the stream corridor. The mixed forested habitat provides a relatively heterogeneous habitat for wildlife, and the Phillips Creek riparian system is proximal to and at some points connected with the Merrill and Ring Creek and Glenwood Creek riparian systems, providing wildlife corridors and habitat linkages between the drainages. The presence of a relatively diverse representation of plant species, proximity to other drainages, and heterogeneous forested and wetland habitats are suitable for numerous forest-dwelling wildlife species.
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Invasive Species: Invasive plant species in the project vicinity include Himalayan blackberry, reed canary grass, English ivy, and Japanese knotweed. Invasive plant species were most dense in edge habitats such as the steep marine bluff and along the habitat interface between the Phillips Creek riparian system and surrounding yards, roads, etc.
H. Summary of Habitat Characteristics and Identified Issues
Based on the stream habitat survey data for Phillips Creek, land use patterns, and other available information, the following general habitat characteristics pertain for this system. Identified habitat issues are summarized in Table 7-6, and their locations are shown on Figure 7-4.
Table 7-6 Identified Habitat Issues Issue ID Location Issue1 PH-A Mouth of Phillips Creek BNSF railway Total fish barrier Extremely high gradient and velocity, total fish PH-B Phillips Creek bay bluffs barrier PH-C Phillips Creek crossing W Mukilteo Boulevard Partial fish barrier 1Fish barriers identified by WDFW
Phillips Creek may be characterized as a small stream system that descends and down cuts through a steep marine bluff overlooking Port Gardner Bay, draining a small portion of the overall area of that bluff. As such, there is limited flow/hydrology in upper Phillips Creek. The flow regime in the upper system is seasonal, drying up in summer. Due to an absence of flows during the summer, resident fish presence is very likely precluded in the upper system. Anadromous fish are absent in the system due to naturally occurring gradient barriers at the marine bluff above Port Gardner, and resident fish presence is unlikely due to flow regimes and the small stream size.
Phillips Creek shows riparian and terrestrial habitat that has been impacted by surrounding residential development. The surveyed habitat reach displayed large wood in sufficient quantities, although the large wood is limited in size, with an associated reduction in full habitat potential and pool formation functions. Due to the relatively narrow riparian corridor, the riparian and terrestrial habitats present are likely to support a somewhat limited diversity and abundance of native vegetation and fauna. The forested canopy and stream shading appear adequate for the system.
There is aquatic instream habitat loss from excessive sedimentation within the system due to landwasting slides and erosion. There is also a lack or loss of pool habit as a result of fine sediment in-filling of portions of stream channel. Lack of pool habitat limits high flow refugia for fish (if present) and limits low flow and thermal buffering (cooling) refugia for fish (if present). Potential spawning habitat and habitat for stream invertebrates is likely degraded as a result of fine sediment depositing in riffle habitat.
There are potential fish passage barriers associated with two culverts (W Mukilteo Boulevard and BNSF railway culvert) and complete barriers associated with naturally occurring stream gradients and cascades associated with the marine bluff.
Wetlands associated with Phillips Creek provide some degree of water quality and storage functions, although these functions are limited by the size of the wetlands and the overall size of the riparian corridor. These wetlands provide invertebrate and wildlife habitat functions and complexity.
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7.2 Basin Analyses and Issue Severity Rating
A. Basin Modeling
The three goals of the surface water comprehensive planning process focus on water flow, water quality, and habitat. A qualitative analysis was performed for each of the three goals; a quantitative analysis was also performed for water flow. The analysis developed average seasonal flows for the Phillips Creek basin (Table 7-2) and the frequency of peak flows in Phillips Creek.
Hydrologic modeling was used to develop projects. Existing conditions flow rates were used for issue identification while future land use (with climate change) was used when sizing improvements to reduce inundation at project locations. Peak flow (15 minute interval) modeling results at the outfall are provided in Table 7-7 to demonstrate the change in flow rates between existing and future conditions for the 2-year and 25-year events.
Table 7-7 Peak Flows at Select Creek Location (CFS) Existing Land Use Future Land Use with with Historic Climate Change Sub- Location2 Precipitation Precipitation basin 2-year 25-year 2-year 25-year (FF)1 (FF)1 (FF)1 (FF)1 PH-1 Main stem at Outfall 10.5 22.1 14.4 32.2 1FF: Flood Frequency return interval 2Peak Flows are recorded for the location at which runoff discharges from the subbasin
B. Summary of Identified Issues
Basin issue locations were identified through the basin characterization and evaluation process for water flow, water quality, and habitat. These issues are associated with public right-of-way and infrastructure systems, or are generally system-wide in the case of habitat issues. The issue locations are shown in Figure 7-4 and the key issues at those locations are listed in Table 7-8.
Table 7-8 Summary of Identified Issues Issue ID Location Key Issue PH-A Mouth of Phillips Creek at BNSF railway Habitat PH-B Phillips Creek though the bay bluffs Habitat PH-C Phillips Creek crossing W Mukilteo Boulevard Habitat
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O IDENTIFIED ISSUES L oun d Y S M on P s i I s R C se D B s F LV o CITY OF EVERETTIF D L P C E AV 2014 NA RO AD A M BLVD EO T IL H K U R I M D G W E M O N T
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L N V E AD Issue Identification K XX Issue Type: HARDESON RD WF = Water Flow ³ WQ = Water Quality H = Habitat Disclaimer: The information shown in this map is assembled GIS data created and acquired by Otak Inc., City of Everett, and from Snohomish County GIS. This data is not to survey accuracy and is meant for planning purposes only. FLU WY K ES DR 0 500 1,000 2,000 SHUKSAN WAY SIEVERS-DUECYFeet BLVD G:\Projects\SWCP_Port_Gardner\IdentifiedIssuesMaps\PhillipsCreek_IdentifiedIssues.mxd Chapter 7—Phillips Creek Basin Plan
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C. Issues Severity Rating
The identified issues were rated on 13 different criterion based on issue severity in terms of water flow, water quality, and habitat. The score ranged from one to five, with five being the most severe. Issues were given a score of zero if the criterion was not applicable to the issue. Table 7-9 shows criteria and corresponding score range and Table 7-10 rates each of the issue locations based on each criterion.
Table 7-9 Identified Issue Severity Criteria Criterion Discipline Specific Score Range Number 1 = Landscape 1 Water flow Asset Impacted 3 = Street 5 = Building 1 = Isolated, one lot 2 Water flow Extent Impacted 3 = Multiple, several properties 5 = Widespread or corridor 1 = 25-year storm 3 Water flow Frequency of Impact 3 = 10-year storm 5 = 1-year storm or more frequent 1 = Minor – Ponding 4 Water flow Magnitude of Impact 3 = Moderate – Flowing water 5 = Severe – Endangers human well-being 1 = Little concern, low pollution concentration Severity level of water 3 = Opportunity for water quality enhancement, medium 5 Water quality quality concentration concentrated pollutant 5 = TMDL-related, high concentrated pollutant source. 1 = Systemic water quality issue, with no real point Extent of extent of water sources quality problem and 3 = Systemic water quality issue, with point sources that 6 Water quality effectiveness of single provides opportunity for WQ enhancement project to improve 5 = Local/point WQ issue with significant opportunity to improve WQ 1 = Private water quality staying on private property Water Quality Issue 7 Water quality 3 = MS4 water quality staying on public property Location 5 = MS4 water quality flowing onto private property 1 = Low levels of habitat issues Substrate composition, 8 Habitat 3 = Moderate levels of habitat issues embeddedness of fines 5 = High levels of habitat issues Presence and potential 1 = Low levels of habitat issues 9 Habitat for recruitment of woody 3 = Moderate levels of habitat issues debris 5 = High levels of habitat issues 1 = Low levels of habitat issues Frequency and quality of 10 Habitat 3 = Moderate levels of habitat issues pool habitat by reach 5 = High levels of habitat issues 1 = Low levels of habitat issues Riparian community 11 Habitat 3 = Moderate levels of habitat issues composition, size, quality 5 = High levels of habitat issues Flow conditions, 1 = Low levels of habitat issues 12 Habitat seasonality, ability to 3 = Moderate levels of habitat issues support aquatic biota 5 = High levels of habitat issues 1 = Isolated wetland 13 Habitat Water resource impacted 3 = Non-riparian creek 5 = Fish-bearing stream or lake
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Table 7-10 Phillips Creek Identified Issue Severity Rating Water Flow Score by Water Water Quality Score By Water Water Identified Issue Water Flow Habitat Score by Criterion Habitat Habitat Level Total Issue Severity Issue Criterion Normalized Weighting Flow Level Criterion Normalized Weighting Quality Quality Level Normalized Weighting Description/Location/ Discipline Discipline of Rating - All Category ID Average1 Factor of Average1 Factor Discipline of Average1 Factor Key Issue Type(s) 1 2 3 4 Total 5 6 7 8 9 10 11 12 13 Total Importance Disciplines2 Importance Total Importance BNSF railway crossing - PH-A N/A N/A N/A N/A 0.00 50 0.0 1 N/A N/A N/A 0.00 30 0.0 2 4 1 4 1 2 5 0.57 20 11 1 11.3 PVP fish barrier Habitat
High gradient through PH-B N/A N/A N/A N/A 0.00 50 0.0 1 N/A N/A N/A 0.00 30 0.0 2 4 1 4 1 3 4 0.57 20 11 1 11.3 NP bay bluffs Habitat
Mukilteo Blvd crossing PH-C N/A N/A N/A N/A 0.00 50 0.0 1 N/A N/A N/A 0.00 30 0.0 2 3 1 2 1 1 4 0.40 20 8 4 8.0 PP - undersized culvert Habitat
N/A = not applicable - either condition does not exist or desktop analysis concluded a low probability of any significant problem existing. Score for N/A = 0. Issue Category Legend
1 Normalized average = average score of listed criterion for discipline divided by maximum possible criterion score value of 5 CB = Condition-Based NP = Natural Process
2 Maximum possible total scores: E = Enforcement/Education PVP = Private Property
Water flow = 50 X = Extreme Event PP = Public Property
Water quality = 30 J = Jurisdiction R = Resolved
Habitat = 20 LS = Low Score UGA = Urban Growth Area
All three disciplines = 100 M = Maintenance
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7.3 Recommended Projects
The basin issues rated for severity in Table 7-10 were also categorized; see the categories in the last column of the table and the legend of categories below the table on the right-hand side. Projects were considered for basin issues on public property (PP) and with a severity rating above ten (the low score (LS) threshold). Identified issues on private property (PVP) are listed here and in Volume I for reference. Private property issues are the responsibility of the private property owner to remedy; although non-profit agencies, such as Adopt-A-Stream or the Snohomish Conservation District, have a history of assisting private property owners with similar issues. Issues categorized as resolved (R) previously had a project implemented and the issue is now resolved. Identified issues in other categories – condition-based (CB), enforcement/education (E), extreme event (X), jurisdiction (J), low score (LS), maintenance (M), natural process (NP), urban growth area (UGA) – are included for reference and not developed into projects. Basin issues are identified in this SWCP so that City staff may coordinate with property owners and other agencies when the City is planning to design and construct a project. Basin issues may become resolved as a result of a change in a related issue, the completion of a related project, or a change in land use.
No improvement projects to address basin issues are recommended at this time.
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