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ThurstonHighWetlandsReport-Jul12-07 416 Washington Street SE, Suite 202 Olympia, WA 98501 (360) 352-9897 (360) 352-9914 fax cootco@olywa.net WETLANDS INVENTORY, WETLAND IMPACTS AND MITIGATION RECOMMENDATIONS FOR THE THURSTON HIGHLANDS MASTER PLANNED COMMUNITY S23, 26, 27 T17N R1E Thurston County, City of Yelm JULY 2007 prepared for: Thurston Highlands, LLC 4200 6th Avenue SE, Suite 301 Lacey, WA 98503 prepared by: Steve Shanewise, PWS Senior Ecologist Thurjuly07inv.doc CONTENTS Introduction 1 Methods 2 Section 1. Wetlands Inventory Results Property Overview 5 Wetlands 6 Table 1.Wetlands Summary 6 Discussion 9 Section 2. Wetland Impacts and Mitigation Recommendations Construction Impacts 11 Table 2. Isolated Wetlands 13 Mitigation for Construction Impacts 14 Table 3. Mitigation Compensation 15 Developed Condition Impacts 15 Mitigation for Developed Condition Impacts 16 Figure 1: Vicinity Map Figure 2: Surveyed Wetlands Map Figure 3: Soil Survey Figure Figure Figure Appendix I: Wetland Descriptions Appendix II: Soil Data Sheets Appendix III: Category Rating Forms References INTRODUCTION This report documents existing wetland conditions within the Thurston Highlands Master Planned Community as well as impacts and mitigation recommendations for proposed project development. This site is proposed for phased development of an approximately 1,240 acre mixed-use Master Planned Community within the city limits of Yelm. The entire property is currently undeveloped land that has been managed for decades for clear-cut forestry. Most of the land supports replanted, even-aged stands of rather monotypic Douglas fir (Pseudotsuga menziesii) forest varying in age from 5 to 25 years. Section 1 of this report describes existing wetland conditions. A total of 35 individual wetland systems were identified throughout the property. Most of these occur in the southern half of the site. Many of these wetlands are small, isolated systems within the bottoms of kettle basins that have no outlet. The largest wetlands onsite occur in the southeast and northeast areas. These systems represent the headwater beginnings to drainage routes that eventually connect to the off-property, Thompson Creek channel approximately one-half mile to the east. Only a single, short (approximately 200ft), Type 5 stream, connecting two wetlands, occurs within the entire project area, emphasizing the depressional topography prevalent throughout the landscape. Category ratings for Thurston Highlands wetlands cover the whole range from Category I to Category IV using the Washington State Wetlands Rating System for Wester Washington Revised (Ecology 2004). Category III systems are most common (23), and include most of the isolated systems (B, C, D, E and G wetland groups.) Category II systems are a distant second in number (8), and include most of the A wetland group plus F. Three Category I conditions occur based upon Special Features (2 Mature Forests and 1 Bog) and there is one Category IV. Regulatory jurisdiction varies widely between the wetlands. Some are too small for regulation by the City of Yelm under it’s Critical Areas Code, and some are isolated and thus not subject to Federal regulation. All wetlands on the site, however, regardless of size and isolation, are subject to Washington Department of Ecology regulations. Section 2 of this report evaluates full build-out of the development over a 10- to 30-year period, and a Phase 1 development scenario. Three conceptual land use alternatives and No Action are evaluated for overall development of the site. The conceptual land use alternatives include: the Preferred Alternative (a hybrid of the less dense and more intensive “bookend” alternatives), Traditional Development, and an Urban Village concept. The Phase 1 conceptual land use plan includes approximately 1,008 homes (single-family detached and multi-family), associated roads and utilities infrastructure. The first phase of development would occur in the northeast corner of the site, as a westward extension of urban residential development within the adjacent Tahoma Terra neighborhood. It is projected that Phase 1 would be constructed between approximately 2008 and 2011, and to be occupied between approximately 2009 and 2012. Beyond a probable first subdivision application, the timing and number of dwelling units to be developed within the Master Planned Community is less certain, subject to market demand. A Phase 1 conceptual land use plan was developed to assist public service providers with quantitative planning for early stages of development within Thurston Highlands, and to provide a basis for more specific, representative impact analysis of proposed development. The Phase 1 site plan, like the three conceptual land use alternatives, however, is still hypothetical at the time of this writing. METHODS Field Review Field review of the Thurston Highlands property for wetland conditions was performed over many days between November 2005 and December 2006. Over this period of time, all areas of the property were traversed on foot while searching for wetland conditions. In addition, topographic maps were used to locate depressional areas, and aerial photographs were used to identify unusual vegetation signatures. All such features were specifically reviewed on the ground for wetland conditions. Wetland Classification Wetland characteristics are described within this report according to the U.S. Fish and Wildlife Service Cowardin Classification System (1989). Wetland Delineation Most delineation work was accomplished in the mid-winter/early spring wet season to afford good interpretation of wetland hydrology. Wetland delineation followed a Routine Methodology based on the Washington State Wetland Identification and Delineation Manual (1997), requiring positive indicators for wetland soil, hydrology, and plants: Wetland hydrology was determined by water conditions in pits. Presence of hydric soil was determined by soil conditions in pits dug around suspected wetlands. Soil inspection included comparison with the Munsell Color Charts (1992). General soil characteristics were derived from information contained within the Soil Survey of Thurston County, Washington (1990). Occurrence of wetland vegetation was determined through species identification, estimation of dominance, and then assignment of wetland indicator status. Indicator status was assigned based upon the National List of Plant Species That Occur In Wetlands (1988), Supplement (1993). State Category Rating The Washington State Wetlands Rating System for Western Washington Revised (2004) was used to establish Category Ratings for the wetlands (Ecology Publication #04-06-025). Wetland Buffers Wetland buffer widths for regulatory purposes as recommended using best professional judgement were developed by following the Washington Department of Ecology Guidance for Protecting and Managing Wetlands: Volume 2 (April 2005). Specifically, buffers were determined using the “Graduated Scale” of Alternative 3A as listed in Table 8C-9, with slight modification. Wetlands less than 4,000 square feet in size with low Habitat Function points (<20) are assigned 75-foot buffers for Category III systems, and a 50-foot buffer for the Category IV system. In addition, wetlands below 1,000 square feet in size are interpreted as “non-jurisdictional” to the City of Yelm, and do not require buffer setbacks. Wetland Labeling Wetlands described for the Thurston Highlands project were separated into eight different groups based on location, proximity and/or similarities in structure and function. This was done to help consolidate text descriptions and avoid repetitive duplication while simultaneously providing a better gestalt view of the overall wetland conditions. SECTION 1. WETLAND INVENTORY RESULTS PROPERTY OVERVIEW Single, Large Property within the Yelm City Limits (Figure 1) The Thurston Highlands property is situated within the city limits of Yelm, Washington, in eastern Thurston County. It is located west of the existing developed area of the city, and occurs between the Fort Lewis Military Reservation to the west, SR-507 to the south, and SR-510 to the north. The Thurston Highlands property covers almost two square miles of landscape in a single, connected unit. Undeveloped Timber Land The entire property consists of undeveloped timber land managed by Weyerhaeuser for clear-cut forestry for decades. Most upland areas of the property support replanted, even-aged, monotypic, Douglas fir forest of varying ages. A network of dirt logging roads accesses all major areas of the property. There are no buildings. Two recently-installed well heads in the southwest corner and an electrical power transmission line corridor crossing the western portion of the property represent the only “developed” land uses at the present time. Detailed descriptions of the upland habitat conditions are provided in a separate Fish and Wildlife Species and Habitats Report prepared for the Thurston Highlands Master Planned Community. (Shanewise, July 2007). Urban Zoning The entire property was annexed to the City of Yelm in July 1994, and is zoned for a Master Planned Community. The cCurrent plans application for conceputal approval of a Master Planned Community for the site calls for developing the site in phases over 10 to 30 years to an eventual build-out of approximately 5,000 homes, a retail/commercial/ office area, a Regional Sports Complex, neighborhood parks, schools, trails and several large areas of natural open space. Adjacent to the Fort Lewis Military Reservation The Fort Lewis Military Reservation borders the Thurston Highlands site on the west and northwest. There is a total of approximately 2.5 miles of shared property boundary. This area of the military reservation consists of mature, second-growth, Douglas fir forest, managed selectively for forest practices and wildlife habitat preservation. There are no developed features on the military reservation within at least one mile of the Thurston Highlands property; however, this area is used for military training maneuvers. Alderwood-Everett Soil Association (Figure 3) The majority of the Thurston Highlands site is situated in the Alderwood-Everett soils association that formed on glacial till plains. These two specific soil types are the most common onsite, with Everett the most common of the two. Other upland soils include large formations of sandy Yelm and Indianola series in the northeast and north-central portions of the property, and Tenino gravelly loam along the west side. In addition, eight formations of Mukilteo muck occur in the southwest property area, all associated with significant wetlands. Hydric Mckenna soils are found at only one location in the northeast corner of Thurston Highlands property where another significant wetland complex occurs. WETLANDS Thompson Creek Watershed The entire Thurston Highlands property is within the Thompson Creek Watershed. The actual Thompson Creek system is situated to the east of this property, and drains north to the Nisqually River. Although Thurston Highlands technically lies within the Thompson Creek Watershed, large portions of the property have no direct drainage connection to this system because the landscape topography has an abundance of closed, depressional basins, both upland and wetland, that lack surface water outlets. Small Kettles Common Small kettle basin wetlands are common within this property. Most of these are located in the southwest portion of the landscape where underlying soils seem to have an impervious condition that perches water. Although similar kettle structures occur in other portions of the property, these are all well-drained and do not support even marginal wetland conditions like those occurring within almost all significant kettles in the southwest area. Regulatory Jurisdiction Regulatory jurisdiction of Thurston Highlands wetlands varies widely. All isolated systems lacking any potential for a surface water outlet, are not regulated by Federal law (i.e., by the U.S. Army Corps of Engineers). In addition, many of these small, isolated systems are below the minimum size for City of Yelm jurisdiction under the adopted Critical Areas Code. Regardless of size or isolation status, however, all wetlands within Thurston Highlands will be regulated by the Washington Department of Ecology (WDOE) and will be considered in the Environmental Impact Statement. Table 1. Thurston Highlands – Wetlands Summary Wetland Size/ Acres Category Rating/ Habitat pts Buffer Jurisdiction A1 0.55 II / 19 100’ Yelm, DOE A2 1.10 II / 17 100’ Yelm, DOE, ACOE A3 1.28 II / 21 100’ Yelm, DOE, ACOE A4 0.49 II / 17 100’ Yelm, DOE, ACOE A5 14.01 I and II / 24 160’/250’Bog Yelm, DOE, ACOE Wetland Size/ Acres Category Rating/ Habitat pts Buffer Jurisdiction A6 2.33 onsite II / 18 100’ Yelm, DOE, ACOE A7 3.06 onsite III / 20 100’ Yelm, DOE, ACOE A8 23.66 Onsite I / 23 140’ Yelm, DOE, ACOE B 4.54 onsite II / 21 100’ Yelm, DOE, ACOE C1 0.47 III / 17 100’ Yelm, DOE C2 0.30 III / 17 100’ Yelm, DOE C3 0.03 III / 18 75’ Yelm, DOE D1 0.66 III / 14 100’ Yelm, DOE D2 0.23 III / 18 100’ Yelm, DOE D3 0.07 III / 18 75’ Yelm, DOE D4 0.06 III / 18 75’ Yelm, DOE D5 0.07 III / 18 75’ Yelm, DOE D6 0.04 III / 15 75’ Yelm, DOE D7 0.05 III / 17 75’ Yelm, DOE D8 0.04 III / 17 75’ Yelm, DOE D9 0.02 III / 17 No Buffer DOE D10 0.02 III / 17 No Buffer DOE D11 0.02 III / 17 No Buffer DOE D12 0.01 III / 17 No Buffer DOE Wetland Size/ Acres Category Rating/ Habitat pts Buffer Jurisdiction D13 0.07 III / 17 75’ Yelm, DOE D14 0.06 IV / 7 50’ Yelm, DOE E1 0.30 III / 17 100’ Yelm, DOE E2 0.01 III / 17 No Buffer DOE E3 0.04 III / 17 75’ Yelm, DOE F 2.42 onsite II / 19 100’ Yelm, DOE, ACOE G1 0.52 III / 18 100’ Yelm, DOE G2 0.18 III / 18 100’ Yelm, DOE H1 8.47 III / 23 140’ Yelm, DOE, ACOE H2 0.55 III / 19 100’ Yelm, DOE, ACOE H3 1.89 onsite I and III / 21 100’ Yelm, DOE, ACOE Trace Technical “Stream” Condition To further illustrate the significant depressional structure of the Thurston Highlands landscape, there is only a single, short drainage route connecting wetland A6 to A5 that forms the technical definition of a stream condition: a scour channel with defined Ordinary High Water Marks. This is unusual for such a large piece of land in a climate with 40 inches of average annual precipitation. Where any other flowing surface water occurs, it is a seasonal condition confined within a wetland swale but not a scoured stream channel. These flowing surface water conditions occur within only four, limited locations along the three outlet drainage systems on the property. Three Drainage Routes Only three drainage routes occur within the Thurston Highlands property that have a direct, connected outlet to Thompson Creek. The two largest of these occur in the southeast portion of the property. One of these drainage routes has its headwater beginnings within Thurston Highlands, while the other begins well to the south and simply flows through a corner of the property. These two drainages eventually combine off-property into a single drainage route that connects to Thompson Creek. The off-property portions of this combined drainage route have been severely ditched in the past, which has significantly reduced the levels of persistent surface water. The third drainage route, that also begins within Thurston Highlands, occurs in the far northeast corner of the property where a ditched, headwater basin drains to a linear wetland drainage that eventually connects to Thompson Creek. Category Ratings (Appendix III) Category ratings for Thurston Highlands wetlands cover the whole range from Category I to Category IV. Category III systems are most common (23), and include most of the isolated systems (B, C, D, E and G wetland groups.) Category II systems are a distant second in number (8), and include most of the A wetland group plus F. Three category I conditions occur based upon Special Features (2 Mature Forests and 1 Bog) and there is one Category IV. Significant Upland Expanse Of note within this large piece of property are the significant expanses of landscape that lack any wetland conditions. Approximately half or more of the 1,240 acres is completely devoid of wetland conditions, even though surface topography is similar to the areas where wetlands occur. As with the lack of streams, having such large areas of land that lack any wetland conditions, especially given the predominance of depressional, closed basin topography, is fairly unusual in a climate with such high precipitation (approximately 40 inches per year.) Detailed Wetland Descriptions A detailed description of wetland conditions within Thurston Highlands is provided in Appendix I of this report. A total of 35 individual wetlands are identified. For the purposes of this report, the wetlands have been separated into eight groups based on similarities in structure, function and/or proximity. A group description is followed by individual wetland descriptions, with some nearly identical systems having a generic description that pertains to all of them. DISCUSSION Wetland Buffers The wetland buffer methodology developed for this Master Planned Community is fairly similar to that currently enacted by the City of Yelm. The “Graduated Scale” system applied to Thurston Highlands has marginally different incremental changes in buffer widths based on the Habitat Function score within the Category Rating form. In addition, Best Professional Judgment was used to recommend the buffer reduce the widths of buffers on regulated wetlands below 4,000 sqft to avoid encumbering land with excessive buffer areas for very small, isolated wetland systems with low functional values. recognizing that these low value systems will have marginal wildlife habitat value even with extensive buffers in an urban environment. Filling Small Wetlands About one-third of the property wetlands are very small (less than one-tenth of an acre), isolated systems scattered about the landscape. Preserving all of these wetlands in place, with buffers, would be difficult in an urban environment while providing even moderate value as wildlife habitatencumber a significant portion of landscape with planning difficulties for infrastructure layout., bing Furthermore, preserving these small, low- value systems in place would leave them completely surrounded by urban development. It is recommended in this report, for the City’s consideration, to fill these small wetlands and provide compensatory mitigation in the form of new and/or enhanced wetland habitat associated with much larger systems on the property ( wetland complexes that can be protected with upland connections to significant, undeveloped landscape ( for a net gain in habitat function. SECTION 2. WETLAND IMPACTS AND MITIGATION RECOMMENDATIONS CONSTRUCTION IMPACTS Upland Clearing/Grading and Erosion Potential Overall Thurston Highlands Master Planned Community: Clearing and grading activities within areas to be developed would leave large expanses of bare, disturbed ground exposed to the elements. It is estimated that approximately 100 acres would be cleared for each 250-lot subdivision application, under any conceptual land use alternative. As these lots are sold and construction is underway, the next ( 100 acres would be cleared for development. In this manner, only approximately 100 to 300 acres would be cleared, undergoing development, and/or awaiting landscaping at any one time (personal communication with Doug Bloom, Thurston Highlands, L.L.C., May 29, 2007). The potential for erosion of sediments by precipitation will be high. However, potential impacts to property wetlands from any such erosion would be minimal. Existing wetlands are fully vegetated and do not support anadromous fish. There would be very little distinction in clearing, grading and erosion potential impacts between the conceptual land use alternatives. It is possible that with more concentrated development in the Urban Village Alternative and a larger amount of open space to be preserved that it would be possible to avoid wetland and wetland buffer impacts to a greater degree, and/or easier to preserve larger wetland buffers within this alternative. Phase 1: The Phase 1 development area is approximately 350 acres in size. It is possible that most of this site area may be devoid of vegetation at some period of time over the 3- to 4-year period during which development would occur in Phase 1. Potential wetlands impact from erosion within this project area would be especially low. The primary, high-value wetlands within the H complex would be protected with a wide, fully-vegetated upland buffer that far exceeds the width recommended in Section 1 due to the proposal to preserve the Mature Forest habitat adjacent to these wetlands (see Figure XX). Furthermore, any surface water outfall from Phase 1 wetlands would also have to travel….(need to investigate outfall route). High-Value Wetlands Mostly Avoided Overall Thurston Highlands Master Planned Community: Any of the conceptual land use plans for the overall Master Planned Community would avoid and preserve all significant, high-value wetland systems identified herein. It is anticipated that a landscape approach to project layout would be used to protect areas where significant wetlands occur within close proximity to one another. Protective buffers may go beyond the simple linear dimension recommended to incorporate distinctive upland features. For example, buffer protection of the large Wetland A complex could extend to the top of a prominent ridge along the western aspect, rather than simply stopping at the recommended 250 or 140-foot buffer width. Phase 1: The Phase 1 development area contains a large, connected wetland complex (Wetland H) that is a headwater drainage basin to a minor tributary to Thompson Creek. Except for a single, unavoidable road crossing to provide access to an adjacent property (described below), Thurston Highlands Phase 1 development would completely avoid this wetland complex, and protect it by retaining the existing buffer, mostly far in excess of the recommended buffer width. This larger buffer would be preserved in the Mature Forest upland habitat adjacent to the west side of the wetland complex (see Figure XX). Wetland Crossings by Roads Overall Thurston Highlands Master Planned Community: Extension of Tahoma Boulevard through the Thurston Highlands Master Planned Community under any conceptual land use alternative would result in unavoidable wetland crossings at two locations (see Figure XX). This will be necessitated by perimeter access point limitations coupled with the long, linear configuration of wetlands that occur as connected drainages in the northeast and southeast areas of the site. The fixed access points severely restrict options for roadway realignment, and the linear wetland structure prevents avoidance by trying to “go around” the systems. Phase 1: To comply with the City’s “connected streets” policy, a roadway is required to provide access between Thurston Highlands Phase 1 and adjacent residential property to the east. This roadway cannot avoid crossing the high-value Wetland H complex that lies perpendicular to the road alignment. This road will impact approximately xxxx square feet of wetland, and approximately xxxx square feet of wetland buffer. Because the road is required to serve the adjacent (Purvis) property, permit applications for the wetland crossing will be submitted to the appropriate federal, state, and local agencies associated with development applications for that property. [Grant: Please provide the Yelm City Code citation for the “connected streets” policy.] Minor Buffer Adjustments Overall Thurston Highlands Master Planned Community: Minor adjustments to wetland buffers recommended herein may be necessary within the overall project to accommodate a proportioned lot layout design. The generally straight alignment of roads and the generally rectangular shape of lots often conflict with the usually irregular boundaries of wetland buffers. Buffer averaging of the outer 25% of any on-site wetland would not induce a significant increase in impacts. Buffer reductions of the outer 25% of all isolated wetlands would also avoid any significant increase in impacts, provided some type of compensatory mitigation is implemented (such as fencing or plantings). However, buffer reductions should not occur on the larger, high-value wetland systems: the Wetland A and H complexes, as well as Wetland B. The one exception to this “no reduction” recommendation would involve the buffers east of Wetlands A5, A6 and A7, facing the proposed commercial zone. If substantial effort were put forth to shield these wetland systems from potential impacts, especially human access and night lighting, buffer reductions to 100 feet could be considered in these locations. Phase 1: Minor buffer averaging may be used along the southern edge of the Wetland H complex to create a straight edge along the back side of proposed residential lots, if the actual subdivision application is submitted as shown on (or similar to) the Phase 1 conceptual land use plan (see Figure XX). The recommended buffer dimension of 140 feet could be reduced by approximately xx feet at the rear of some lots. Isolated Wetland Fill Overall Thurston Highlands Master Planned Community: There are an unusually high number of isolated wetlands on the Thurston Highlands site (23 of the 35 wetlands identified herein). This is due primarily to the landscape structure in certain areas that supports a large number of kettle basins formed in glacial outwash conditions. Many of these wetlands are small, low-function systems that would be appropriate to fill and compensate the impacts elsewhere on-site by expanding and enhancing a high-value wetland complex. Preserving all of these low-value systems within the landscape could significantly disrupt a development layout under any conceptual land use alternative, especially relative to grading needsbe difficult in an urban environment and would most likely be unsuccessful. To assist with decisions regarding which wetlands to preserve, the following table lists all of these isolated systems in a two-tiered arrangement, with recommendations depicting those that would be preferred to be filled and those that would be acceptable to fill. Table 2. Isolated Wetlands *Impact with Compensation Preferred Wetland Approximate Area D2-D14 30,000 E2, E3 2,500 C3 1,100 G2 8,000 41,600 *Impact with Compensation Acceptable 100,000 2:1 = 212,000 D1 29,000 E1 13,000 G1 22,500 64,500 *Impact can mean either direct fill, or use of the site for stormwater detention Phase 1: Three isolated wetlands within Phase 1 would be impacted by construction if development is proposed as shown on the Phase 1 conceptual land use plan. Wetlands D14, G1 and G2 may be completely eliminated through mass grading as a result of grading to create uniformly level building areas for single-family homes. If this were to occur, the total wetland impact would be approximately 32,900 square feet (0.76 acre). Alternatively, if City decision makers determine that small isolated wetlands should be preserved within Thurston Highlands, the grading plan would need to be revised to avoid these features, with the result that a reduced number of lots could be developed within the Phase 1 project area. MITIGATION FOR CONSTRUCTION IMPACTS Erosion Control Overall Thurston Highlands Master Planned Community: Best Management Practices (BMPs) for erosion control will be implemented during construction activities with any of the conceptual land use alternatives. Silt fencing will be deployed along all development edges bordering wetland buffers and upland areas to be preserved. Temporary stormwater basins will be employed throughout the construction area to detain stormwater runoff and allow sediments to settle out. The Thurston Highlands Drainage and Utility Technical Engineering Report (KPFF 2007) describes proposed Best Management Practices during construction in more detail. Phase 1: BMPs proposed with overall development of the Master Planned Community would also be implemented during Phase 1 development. Roadway Avoidance/Minimization Overall Thurston Highlands Master Planned Community: Wetland crossings by roads should be aligned to avoid as much direct impact (i.e., fill) as possible, under any conceptual land use alternative. However, site-specific situations regarding upland habitat features (e.g., mature trees) should also be taken into consideration. Wetland crossings by roads in the southern portions of the project area (Wetlands A7 and F) should also incorporate an elevated structure design capable of allowing animal passage beneath the roadway. Phase 1: The roadway crossing of the Wetland H complex to access the Purvis property should be designed to avoid and minimize wetland impacts. Consideration has been given for the alignment to cross the continuous drainage feature Wetland H3 at the narrowest point while simultaneously avoiding several, small wetland systems east of the drainage on property not within Thurston Highlands. Compensation for Construction Impacts Overall Thurston Highlands Master Planned Community: Compensation for wetland impacts can be achieved at numerous locations throughout the site, under any conceptual land use alternative. In general, compensating actions would involve the creation of new wetland habitat by expanding the perimeters of some existing wetlands through excavations. Figure XX depicts the preferred areas for potential wetland creation, with a rough estimate of potential square footage. These areas are also ranked (from first to last) in the following table to identify the priority for use as compensatory wetland mitigation. Total potential compensatory mitigation through creation of new wetland habitat could approach approximately 7 acres, which would be more than adequate to offset the maximum potential for the total area of wetland impacts if all isolated systems were filled. Table 3. Mitigation Compensation Wetland Action Approximate Acreage Credit H1 Enhance/Restore 369,000 185,000 B Create 70,000 70,000 A3-4 Create 20,000 20,000 A1-2 Create 30,000 30,000 Phase 1: Compensatory mitigation for wetland impacts within the Thurston Highlands Phase 1 development area will entail enhancement, restoration and creation of wetlands within Wetland H1 as compensation for road construction to provide access to the Purvis propertyadjacent properties. Implementation and maintenance of that compensatory mitigation would be the responsibility of the Purvis property owner. The primary mitigation concept is for enhancement to entail excavation of small pockets of reed canarygrass (Phalaris arundinacea) within the existing wet meadow habitat to both remove the invasive vegetation and increase surface water depth. Restoration would involve construction of a water control structure on the existing outfall ditch that would enable reflooding the drained system. Wetland creation activities would involve excavations of upland ground around the wetland perimeter, primarily an area dominated by Scot’s broom (Cytisus scoparius), to lower ground elevations enough to allow wetland hydrology to occur. Details of this activity are available in a separate report titled Wetland Mitigation Plan for the Purvis Property (Coot Company, July 2007). THIS WILL HAVE TO PART OF THE EIS IF IT’S REFERENCED. DEVELOPED CONDITION IMPACTS Stormwater Runoff Overall Thurston Highlands Master Planned Community: Stormwater runoff from urban environments can adversely affect wetlands in two primary ways. Stormwater can deliver an array of chemical and biological pollutants to downstream wetlands that are washed away from the developed environment. These may include nutrients and herbicides associated with lawn care maintenance, and petroleum product residues associated with automobile use. Additionally, large volumes of stormwater runoff can overwhelm native wetland and stream systems, causing excessive erosion, drowning of nest sites, and a tendency for non-native, invasive plant communities to develop. Some of the isolated kettle basin wetlands within the site could serve as excellent stormwater detention/infiltration ponds because of their depressional structure relative to the surrounding landscape. While the bottom of these kettles is relatively impervious, resulting in wetland conditions, the sides are porous and would allow detained stormwater to infiltrate laterally. Site development could easily create downhill flow from developed areas that would deliver stormwater to these basins. While this situation would not eliminate the kettle basin wetlands, it would greatly diminish their functions (as described above), requiring full compensation for the area impacted. A hierarchical listing of potential isolated wetlands that could be used for stormwater management under any conceptual land use alternative is provided in Table 2. Phase 1: Stormwater runoff impacts described above for the Thurston Highlands Master Planned Community overall would be similar within the Phase 1 development area. Isolated Wetlands Overall Thurston Highlands Master Planned Community: Avoiding the numerous, small, isolated wetlands within the Master Planned Community under any conceptual land use alternative, and protecting them with buffers would not necessarily preserve their existing functions described herein. Indeed, because these systems would be completely surrounded by a developed, urban environment, they would become “postage stamps” of preserved habitat. Wildlife habitat values would mostly disappear as the areas would become overrun with the presence of domestic pets and children. Because these systems are closed depressions, they would likely accumulate wind-blown or discarded trash that could easily find its way into the wetlands. Rather than occurring as attractive, functioning wetland habitats, they would more likely just become degraded systems within an otherwise managed landscape. Steve comment to Vicki: Stormwater facilities can be managed and maintained without any restrictions imposed by a regulated wetland status. Protected wetlands are supposed to be maintained in a “native vegetated state”; stormwater facilities can be artificially landscaped. Vicki comment ??? to Grant: If components of the stormwater management system, would the homeowners association be responsible for keeping them cleaned out?] Phase 1: The potentially adverse effects of preserving isolated wetlands within the overall Master Planned Community could also occur within the Phase 1 development area. MITIGATION FOR DEVELOPED CONDITION IMPACTS Stormwater Management Overall Thurston Highlands Master Planned Community: The proposal under any conceptual land use alternative is to infiltrate on-site all stormwater collected from developed areas. If a decision is made to use some of the isolated kettle basin wetlands for stormwater detention and infiltration, stormwater runoff from developed areas will have been treated in accordance with the Washington Department of Ecology Stormwater Management Manual for Western Washington prior to release to landscape wetlands. Phase 1: The stormwater management proposal for the Phase 1 development area would be the same as that described for the Master Planned Community overall. Compensation for Developed Condition Impacts Methods of compensatory mitigation for construction impacts, described above, could also be implemented for developed condition impacts. APPENDIX I: WETLAND DESCRIPTIONS WETLANDS INVENTORY, WETLAND IMPACTS AND MITIGATION RECOMMENDATIONS FOR THE THURSTON HIGHLANDS MASTER PLANNED COMMUNITY JULY 2007 GROUP - A WETLANDS SOUTHEAST DRAINAGE SYSTEM This wetland complex consists of a series of mostly connected systems that have a seasonal, surface water outlet to Thompson Creek. These wetlands are situated within the largest depressional topography in all of Thurston Highlands, bounded by high, steep slopes along the southern aspect with a single outlet route draining to the northeast. This complex represents by far the largest, most diverse, high quality wetland habitat anywhere on site, and includes small areas of potential Category I bog conditions. While the lower portions of this wetland complex have been severely ditched in the past, upper portions, where the potential Category I conditions occur, still retain the native water regime. All of these wetlands except A1 either do, or could, achieve a surface water outlet to Federally-regulated wetlands/streams during high water conditions. Eight wetlands are individually described in this complex. WETLAND A1 SIZE: 24,175 sqft (0.55 Acre) LANDSCAPE POSITION Wetland A1 is a Depressional, Closed, oval-shaped system that either is, or is very similar to, a kettle basin formed by a large ice block. This system has no potential for a surface water outlet connection to Federally- regulated waters. CLASSIFICATION Wetland A1 has both shrub and emergent habitat conditions, but the shrub class is dominant. Downed woody debris is abundant, and stems from old logging slash that appears to have been specifically pushed into the wetland basin. Hydrology consists of shallow, seasonal surface water that likely dries out by mid-summer on average. The wetland is located atop a small formation of Mukilteo muck, surrounded by upland, Everett soils. Cowardin Dominant Vegetation PALUSTRINE Spiraea douglasii Scrub-Shrub, Broad-Leafed Deciduous Salix lasiandra Seasonally Flooded, Fresh Populus trichocarpa Organic Physocarpus capitatus Typha latifolia BOUNDARY DELINEATION The boundary of Wetland A1 is a generally distinct, topographic edge a couple feet above the basin bottom at the toe of the surrounding, descending slopes. All three parameters of soil, water (hydrology), and plants change abruptly along a fairly level gradient. The following table depicts general field indicators used to delineate the Wetland A1 boundary: WETLAND UPLAND Spiraea douglasii Pseudotsuga menziesii 1 chroma 4 chroma water in pit dry pit BOTH Pteridium aquilinum FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for Wetland A1, and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 3 0 4 1 Groundwater Recharge HIGH Significant seepage potential into adjacent well-drained soils during high water conditions. Sediment Capture HIGH Closed depression with no regular surface water outlet. Stormwater Detention HIGH Closed depression with no regular surface water outlet. Biofiltration LOW Limited emergent habitat; only seasonally persistent surface water. Plant/Animal Habitat Value LOW Small size; only seasonally persistent surface water. Surface Water Runoff Route LOW Isolated basin with no regular surface water outlet. Surface Water Supply LOW Isolated basin with no regular surface water outlet. Flood Attenuation NA Not associated with a Riverine system. CATEGORY RATING: II (59 pts) Score for Water Quality Functions 16 Score for Hydrologic Functions 24 Score for Habitat Functions 19 TOTAL Score for Functions 59 WETLAND A2 SIZE: 47,779 sqft (1.10 Acres) LANDSCAPE POSITION Wetland A2 is a Depressional, Closed, oval-shaped system that either is, or is very similar to, a kettle basin formed by a large ice block. In extreme high water conditions, this system should fill to the point of achieving an overland, surface water outlet that would connect to Wetland A3. CLASSIFICATION Wetland A2 contains only a single shrub class that is dominated by dense Spiraea douglasii. Downed woody debris is abundant, and stems from old logging slash that appears to have been specifically pushed into the wetland basin. Hydrology consists of shallow, seasonal surface water that likely dries out by mid-summer on average. The wetland is located atop a small formation of Mukilteo muck, surrounded by upland, Everett soils. Cowardin Dominant Vegetation PALUSTRINE Spiraea douglasii Scrub-Shrub, Broad-Leafed Deciduous Fraxinus latifolia Seasonally Flooded, Fresh Organic BOUNDARY DELINEATION The boundary of Wetland A2 is a generally distinct, topographic edge a couple feet above the basin bottom at the toe of the surrounding, descending slopes. All three parameters of soil, water (hydrology), and plants change abruptly along a fairly level gradient. The following table depicts general field indicators used to delineate Wetland A2 boundary: WETLAND UPLAND Spiraea douglasii Pseudotsuga menziesii 1 chroma 4 chroma water in pit dry pit BOTH Pteridium aquilinum FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 3 0 4 1 Groundwater Recharge HIGH Significant seepage potential into adjacent well-drained soils during high water conditions. Sediment Capture HIGH Closed depression with no regular surface water outlet. Stormwater Detention HIGH Closed depression with no regular surface water outlet. Biofiltration LOW No emergent habitat; only seasonally persistent surface water. Plant/Animal Habitat Value LOW Small size; only seasonally persistent surface water. Surface Water Runoff Route LOW Isolated basin with no regular surface water outlet. Surface Water Supply LOW Isolated basin with no regular surface water outlet. Flood Attenuation NA Not associated with a Riverine system. CATEGORY RATING: II (56pts) Score for Water Quality Functions 15 Score for Hydrologic Functions 24 Score for Habitat Functions 17 TOTAL Score for Functions 56 WETLAND A3 SIZE: 55,743 sqft (1.28 Acres) LANDSCAPE POSITION Wetland A3 is a Depressional, Closed system that either is, or is very similar to, a kettle basin formed by a large ice block. In extreme high water conditions, this system should fill to the point of achieving an overland, surface water outlet that would connect to Wetland A5. CLASSIFICATION Wetland A3 is dominated by forested and open water habitats, with only a small area of shrub class. Hydrology is at least seasonal, and may be semi-permanent. Open water areas may support aquatic bed vegetation, but the winter time review of this system could not determine the status of this condition. Woody debris is again abundant within this wetland, stemming from logging debris that appears to have been pushed into the basin. This system also has a few snags. The wetland is located atop a small formation of Mukilteo muck, surrounded by upland, Everett soils. Cowardin Dominant Vegetation PALUSTRINE Populus tremuloides Forested, Broad-Leafed Deciduous Spiraea douglasii Aquatic Bed, Rooted Vascular Carex obnupta Seasonally Flooded, Fresh Fraxinus latifolia Organic BOUNDARY DELINEATION The boundary of this wetland is a generally distinct, topographic edge a couple feet above the basin bottom at the toe of the surrounding, descending slopes. All three parameters of soil, water (hydrology), and plants change abruptly along a fairly level gradient. The following table depicts general field indicators used to delineate this wetland boundary: WETLAND UPLAND Spiraea douglasii Pseudotsuga menziesii 1 chroma 4 chroma water in pit dry pit BOTH FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 3 1 3 1 Groundwater Recharge HIGH Significant seepage potential into adjacent well-drained soils during high water conditions. Sediment Capture HIGH Closed depression with no regular surface water outlet. Stormwater Detention HIGH Closed depression with no regular surface water outlet. Plant/Animal Habitat Value MOD Open water areas with potentially semi-permanent hydrology. Biofiltration LOW No emergent habitat. Surface Water Runoff Route LOW Isolated basin with no regular surface water outlet. Surface Water Supply LOW Isolated basin with no regular surface water outlet. Flood Attenuation NA Not associated with a Riverine system. CATEGORY RATING: II (64 pts) Score for Water Quality Functions 15 Score for Hydrologic Functions 28 Score for Habitat Functions 21 TOTAL Score for Functions 64 WETLAND A4 SIZE: 21,270 sqft (0.49 Acre) LANDSCAPE POSITION Wetland A4 is a Depressional, Closed system set within a narrow, linear trough within a gently rolling landscape. This small wetland occurs within mineral soil, and does not appear to have been formed by an ice block. In extreme high water conditions, this system should fill to the point of achieving an overland, surface water outlet back to Wetland A3. CLASSIFICATION This wetland supports a dense stand of aspen trees (Populus tremuloides) with a mostly dense understory of sedge (Carex obnupta). Surface water is very shallow, less than one foot of persistent depth, and likely dries out by late spring or early summer. Cowardin Dominant Vegetation PALUSTRINE Populus tremuloides Forested, Broad-Leafed Deciduous Carex obnupta Seasonally Flooded, Fresh Mineral BOUNDARY DELINEATION Most of Wetland A4 boundary is a distinct topographic edge within the adjacent slopes slightly above the generally flat bottom. However, the northwest “arm” of this system loses its adjacent, slope ground, and delineation here becomes problematic as plant and soil conditions lose the clear distinction of the sloped areas. The following table depicts general field indicators used to delineate the Wetland A4 boundary: WETLAND UPLAND Carex obnupta Pseudotsuga menziesii 1 chroma 4 chroma water in pit dry pit BOTH Everett Soil FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 3 0 4 1 Groundwater Recharge HIGH Significant seepage into adjacent well-drained soils during high water conditions. Sediment Capture HIGH Closed depression with no regular surface water outlet. Stormwater Detention HIGH Closed depression with no regular surface water outlet. Biofiltration LOW No emergent habitat; only seasonally persistent surface water. Plant/Animal Habitat Value LOW Small size; only seasonally persistent surface water. Surface Water Runoff Route LOW Isolated basin with no regular surface water outlet. Surface Water Supply LOW Isolated basin with no regular surface water outlet. Flood Attenuation NA Not associated with a Riverine system. CATEGORY RATING: II (53 pts) Score for Water Quality Functions 12 Score for Hydrologic Functions 24 Score for Habitat Functions 17 TOTAL Score for Functions 53 WETLAND A5 SIZE: 610,034 sqft (14.01 Acres) LANDSCAPE POSITION: Wetland A5 is a Depressional, Outflow system set within an irregularly shaped basin with generally steep, adjacent slopes to the west, south and east but gently rolling landscape to the north along the outlet path. This wetland drains to Wetland A7. CLASSIFICATION The large Wetland A5 system is structurally complex with a dense, inter-mixed growth of shrub and emergent classes. Some interior open water or aquatic bed habitats occur, but these are not viewable or accessible from the perimeter uplands. Category I bog conditions likely occur within some of these interior surface water areas; at least one Labrador-tea (Ledum groenlandicum) plant community can be seen with binoculars, and since the wetland is sitting atop deep muck soils, bog habitat should be assumed until proven otherwise. However, these potential Category I conditions appear confined to small areas within the interior portions of the western arm of the wetland. System hydrology is permanent, and seasonal fluctuation is generally minor due to the wide, swale outlet. A small portion of this wetland has been cut-off by a culverted logging road at the tip of the southern arm of the wetland. Cowardin Dominant Vegetation PALUSTRINE Typha latifolia Scrub-Shrub, Broad-Leafed Deciduous Carex obnupta Emergent, Persistent Oenanthe sarmentosa Permanently Flooded, Fresh Spiraea douglasii Organic Salix lasiandra Ledum groenlandicum Rhamnus purshiana BOUNDARY DELINEATION The boundary of Wetland A5 is a generally distinct, topographic edge a couple feet above the basin bottom at the toe of the surrounding, descending slopes. All three parameters of soil, water (hydrology), and plants change abruptly along a fairly level gradient. The following table depicts general field indicators used to delineate this wetland boundary: WETLAND UPLAND Spiraea douglasii Pseudotsuga menziesii 1 chroma 4 chroma water in pit dry pit BOTH 2 chroma FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 3 3 1 1 Biofiltration HIGH Dense emergent and shrub growth within shallow, permanent surface water. Plant/Animal Habitat Value HIGH Large, structurally diverse, permanent surface habitat with potential bog conditions. Sediment Capture HIGH Dense emergent and shrub growth with negligible water flow movement. Stormwater Detention MOD Large, depressional basin but wide outlet limits detention capacity. Surface Water Runoff Route MOD Headwater beginning to continuous drainage route. Surface Water Supply MOD Should sustain a surface water outlet to Thompson Creek into early summer. Groundwater Recharge LOW Underlying soils are muck; minimal rise in persistent surface water levels limits side seepage into surrounding upland soils. Flood Attenuation NA Not associated with a Riverine system. CATEGORY RATING: I/II (55 pts) Category I based on potential bog plant community. Score for Water Quality Functions 11 Score for Hydrologic Functions 20 Score for Habitat Functions 24 TOTAL Score for Functions 55 WETLAND A6 SIZE: 101,543 sqft (2.33 Acres) On-site LANDSCAPE POSITION Wetland A6 is a Depressional, Outflow system set within an oval basin with mostly steep side slopes. This system drains to Wetland A5 along a narrow wetland swale. CLASSIFICATION Wetland A6 sits atop a formation of Mulkilteo muck, and is surrounded by Everett and Alderwood soils. It is a mixed forest and shrub habitat with a mostly solid growth of deciduous woody species. Past drainage of the system apparently occurred when a culvert was placed beneath the logging road that now forms the outlet and reduced persistent surface water levels by approximately one foot. Two, narrow “arms” on this wetland extend east from the main basin up to very small, oval basins. This wetland represents the headwater beginning to a continuous outlet drainage route that eventually connects to Thompson Creek. Cowardin Dominant Vegetation PALUSTRINE Salix lasiandra Forested, Broad-Leafed Deciduous Salix sitchensis Scrub-Shrub, Broad Leaved Deciduous Spiraea douglasii Seasonally Flooded, Fresh Carex obnupta Organic BOUNDARY DELINEATION The boundary of Wetland A6 is clearly displayed by vegetation patterns where salal (Gaultheria shallon) stops and sedge begins. Soils are very indistinct due to past drainage activities, and support hydric soil characteristics on both sides of the boundary. The following table depicts general field indicators used to delineate this wetland boundary: WETLAND UPLAND Carex obnupta Gaultheria shallon saturation in pit dry pit BOTH 1 chroma Muck soils FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 2 4 1 1 Sediment Capture HIGH Depressional structure with dense vegetation and constricted outlet. Stormwater Detention HIGH Deep, depressional structure with single culvert outlet. Biofiltration MOD Dense shrub community with shallow, seasonal surface water persistence. Plant/Animal Habitat Value MOD Dense shrub/tree habitat with shallow, seasonal surface water. Surface Water Runoff Route MOD Headwater beginning to continuous drainage route. Surface Water Supply MOD Seasonal runoff supplied to Wetland A5. Groundwater Recharge LOW Underlying muck soils. Flood Attenuation NA Not associated with Riverine system. CATEGORY RATING: II (57 pts) Score for Water Quality Functions 15 Score for Hydrologic Functions 24 Score for Habitat Functions 18 TOTAL Score for Functions 57 WETLAND A7 SIZE: 133,322 sqft (3.06 Acres) LANDSCAPE POSITION Wetland A7 is a linear swale system that has both Slope and Depressional, Outflow hydrogeomorphic structure. The system acts as the surface water outlet connection between Wetlands A5 and A8. System width is greater near the Wetland A5 outlet, but becomes increasingly narrower as it moves toward the outlet to Wetland A8. CLASSIFICATION Wetland A7 is a forested habitat primarily dominated by aspen trees (Populus tremuloides). A dense shrub understory is also present that varies from mostly salmonberry (Rubus spectabilis) within the wider, southern portions, to an increasingly dense growth of ninebark (Physocarpus capitatus) toward the narrowing, northern outlet. Emergent vegetation is limited by the dense, overhead canopy of shrubs and trees. Shallow, flowing surface water occurs seasonally, but technical stream conditions do not occur (no defined scour channel) due to the width and fully vegetated condition of the drainage swale. Wetland A7 is crossed by a culverted logging road at a narrow portion to the north. Cowardin Dominant Vegetation PALUSTRINE Populus tremuloides Forested, Broad-Leafed Deciduous Rubus spectabilis Seasonally Flooded, Fresh Physocarpus capitatus Organic/Mineral Carex obnupta BOUNDARY DELINEATION Most edges of Wetland A7 occur as indistinct boundaries due to both the low profile of the adjacent uplands and the often mosaic conditions of the landscape. Most flagging extended out far enough to incorporate much of the wetland mosaic, which then including some significant portions of upland “islands” within the delineated boundary. Careful review of soil conditions was constantly needed to determine In/Out status for technical wetland conditions. The following table depicts general field indicators used to delineate the Wetland A7 boundary: WETLAND UPLAND Carex obnupta Gaultheria shallon 1 chroma 4 chroma water in pit dry pit BOTH 2 chroma Populus trichocarpa Physocarpus capitatus Rubus spectabilis FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 1 2 5 0 Surface Water Runoff Route HIGH Only drainage outlet route for wetlands A1, A2, A3, A4, A5 and A6. Flood Attenuation MOD Although not technically Riverine, the dense woody vegetation should slow sheet-flowing water. Surface Water Supply MOD Should sustain a surface water outlet to Thompson Creek into early summer. Biofiltration LOW Lacks significant emergent cover; only seasonally persistent, shallow, sheet-flowing surface water. Groundwater Recharge LOW Some poorly drained, underlying muck soils; only seasonal persistence of sheet-flowing surface water. Plant/Animal Habitat Value LOW Lacks significant structural diversity; only shallow, seasonal surface water persistence. Sediment Capture LOW Mostly sheet flowing surface water with limited emergent cover. Stormwater Detention LOW Lacks significant depressional structure; unrestricted surface water outlet. CATEGORY RATING: III (42 pts) Score for Water Quality Functions 10 Score for Hydrologic Functions 12 Score for Habitat Functions 20 TOTAL Score for Functions 42 WETLAND A8 SIZE: 130,358 sqft (23.66 Acres) LANDSCAPE POSITION Wetland A8 is a Depressional, Outflow system set within the lowest point of ground at the edge where gently rolling, sloped land meets gently rolling, flat land. This system drains to off-property wetlands not described here. CLASSIFICATION Wetland A8 is a Mature Forested habitat that contains large specimens of red alder (Alnus rubra), black cottonwood (Populus trichocarpa), and western red cedar (Thuja plicata), in that order. A dense shrub understory prevails in most areas, with some localized areas of slough sedge (Carex obnupta) where openings in the deciduous canopy allowed better sunlight. The landscape is very hummocky, and some areas of mosaic wetland/upland conditions occur. Hydrology has been severely altered by past ditching along the outlet route that probably reduced the level of persistent surface water in this wetland by 2 feet. However, the existing plant community has grown with this change and is therefore adapted to it, indicating how long ago the drainage action occurred as reflected in the age of the trees. The existing water regime supports shallow, seasonal surface water, but may support permanently saturated soils. Wetland A8 is set atop a formation of drained Mukilteo muck, surrounded by Everett and Alderwood soils. Cowardin Dominant Vegetation PALUSTRINE Alnus rubra Forested, Broad-Leafed Deciduous Populus trichocarpa Seasonally Flooded to Permanently Saturated, Fresh Thuja plicata Organic Physocarpus capitatus Ditched Rubus spectabilis Carex obnupta BOUNDARY DELINEATION Most of the Wetland A8 boundary is very indistinct, largely due to the past drainage actions that have effectively drained the outer perimeter of the original wetlands. Because this original, pre-drained perimeter mostly extended into the toes of the surrounding upland soils while it now is completely confined to the muck soil, constant checking of hydrology conditions was necessary to delineate this wetland boundary. This effectively drained condition coupled with the hummocky landscape made delineation problematic. The following table depicts general field indicators used to delineate this wetland boundary: WETLAND UPLAND Carex obnupta Polystichum munitum water in pit dry pit BOTH Alnus rubra Populus trichocarpa Thuja plicata FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 5 2 1 0 Flood Attenuation HIGH Although not Riverine, significant surface water flows occur through dense, woody vegetation and a disruptive, mosaic ground surface. Plant/Animal Habitat Value HIGH Category I Mature Forest habitat. Sediment Capture HIGH Significant mosaic topography of “isolated” small depressions throughout wetland. Stormwater Detention HIGH Significant mosaic topography of “isolated” small depressions throughout wetland. Surface Water Runoff Route HIGH Drainage outlet route for all of Wetland A Group wetlands. Biofiltration MOD Shallow sheet flow through some emergents and dense shrubs/trees. Surface Water Supply MOD May supply late spring flows to the Thompson Creek system. Groundwater Recharge LOW Underlying muck soils do not drain well. CATEGORY RATING I (Mature Forest) Wetland A8 qualifies for a Category I rating based on the Special Characteristics methodology for a Mature Forest habitat condition. Based on the point total for the Functions methodology, the wetland qualifies for a high point, Category II system. Score for Water Quality Functions 28 Score for Hydrologic Functions 12 Score for Habitat Functions 23 TOTAL Score for Functions 63 GROUP - B WETLAND SOUTHWEST OUTLET BASIN One wetland is described for the southwest outlet basin SIZE: 197,641 sqft (4.54 Acres) LANDSCAPE POSITION Wetland B is a Depressional, Outflow system located in the extreme southwest property corner that drains southwest, off-property to an isolated, kettle basin. The wetland is set within a minor depression within a nearly flat, gently rolling upland landscape. CLASSIFICATION Approximately 90% of Wetland B is dominated by a dense, often monotypic community of spiraea (Spiraea douglasii), with some small, perimeter areas of forested red alder (Alnus rubra) habitat. Hydrology is seasonal within some shallow perimeter areas, but may be semi-permanent to permanent within the lowest portions of the interior basin where the dense spiraea occurs. A dirt road crosses the outlet route for this wetland that parallels the west side of the Thurston Highlands property boundary here. This wetland is set atop a large formation of Mukilteo muck, surrounded by upland Tenino soils. Cowardin Dominant Vegetation PALUSTRINE Spiraea douglasii Scrub-Shrub, Broad-Leafed Deciduous Fraxinus latifolia Forested, Broad-Leafed Deciduous Alnus rubra Seasonally Flooded to Semi- or Permanently Rosa pisocarpa Flooded, Fresh Rubus spectabilis Organic Crateaegus douglasii Carex obnupta Oenanthe sarmentosa BOUNDARY DELINEATION Most of the Wetland B boundary is a distinct edge near the top of a brief, abrupt slope that drops from the surrounding upland landscape to the wetland basin. Soil, water and plant conditions all change abruptly within a couple feet along a mostly level elevation around the wetland perimeter. The following table depicts general field indicators used to delineate the Wetland B boundary: WETLAND UPLAND Carex obnupta Polystichum munitum 1 chroma 3 chroma BOTH Alnus rubra Rubus spectabilis FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 2 2 3 1 Sediment Capture HIGH Large, depressional basin filled with very dense spiraea growth. Stormwater Detention HIGH Large, depressional basin with constricted outlet and 2 to 3 feet of storage capacity. Biofiltration MOD Possibly semi-permanent to permanent surface water with dense shrub growth. Plant/Animal Habitat Value MOD Monotypic habitat structure, but persistent surface water conditions should provide local drinking water source. Groundwater Recharge LOW Underlying muck soils and hardpan in surrounding uplands. Surface Water Runoff Route LOW Headwater basin with no continuous outlet route. Surface Water Supply LOW Headwater basin with no continuous outlet route. Flood Attenuation NA Not associated with a Riverine system. CATEGORY RATING: II (60 pts) Score for Water Quality Functions 15 Score for Hydrologic Functions 24 Score for Habitat Functions 21 TOTAL Score for Functions 60 GROUP ( C WETLANDS KETTLE CLUSTER The three Group C kettle systems are all situated within the same general landscape depression. The two larger wetlands are essentially identical in structure and function, and are therefore given one description that applies to both. All three wetlands are strictly isolated, and would never achieve a surface water outlet to Federally-regulated wetlands or streams. WETLAND C1 and C2 SIZE: C1 20,394 sqft (0.47 Acre) C2 13,216 sqft (0.30 Acre) LANDSCAPE POSITION Both Wetlands C1 and C2 are Depressional, Closed systems set within kettle basins within the low points of a much larger landscape depression. These wetlands have no potential for a surface water outlet connection to Federally-regulated waters. CLASSIFICATION Both Wetlands C1 and C2 are dominated by shrub communities that are in turn dominated by dense spiraea (Spiraea douglasii). Wetland C1 has approximately 95% coverage by spiraea, while Wetland C2 has about 50% coverage. The thick shrub canopy prevents the growth of a significant emergent component within these wetlands. Both systems are full of large woody debris from past logging, but neither have any snags. Hydrology is assumed to be seasonally, but persistence may extend well into summer. Neither Wetland C1 or C2 has mapped organic soils, but Mukilteo muck likely occurs at least centrally within the wetland basin, surrounded by the mapped Everett soils. Cowardin Dominant Vegetation PALUSTRINE Spiraea douglasii Scrub-Shrub, Broad-Leafed Deciduous Salix lasiandra Seasonally Flooded, Fresh Salix sitchensis Organic/Mineral BOUNDARY DELINEATION The boundaries of Wetlands C1 and C2 are a generally distinct, topographic edge a couple feet above the basin bottom at the toe of the surrounding, descending slopes. All three parameters of soil, water (hydrology), and plants change abruptly along a fairly level gradient. The following table depicts general field indicators used to delineate the Wetland C1 and C2 boundaries: WETLAND UPLAND Spiraea douglasii Pseudotsuga menziesii 1 chroma 3 chroma water in pit dry pit BOTH 2 chroma FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 3 0 4 1 Groundwater Recharge HIGH Significant seepage potential into adjacent well-drained soils during high water conditions. Sediment Capture HIGH Closed depression with no regular surface water outlet. Stormwater Detention HIGH Closed depression with no regular surface water outlet. Biofiltration LOW No emergent habitat; only seasonally-persistent surface water. Plant/Animal Habitat Value LOW Dense, monotypic spiraea; only seasonally-persistent surface water. Surface Water Runoff Route LOW Isolated basin with no regular surface water outlet. Surface Water Supply LOW Isolated basin with no regular surface water outlet. Flood Attenuation NA Not associated with a Riverine system. CATEGORY RATING: C1 and C2: III (49 pts) Score for Water Quality Functions 16 Score for Hydrologic Functions 16 Score for Habitat Functions 17 TOTAL Score for Functions 49 WETLAND C3 SIZE: 1,174 sqft (0.03 Acre) LANDSCAPE POSITION Wetland C3 is a Depressional, Closed system set within a kettle basin within the low point of a much larger landscape depression. This system has no potential for a surface water outlet connection to Federally- regulated waters. CLASSIFICATION Wetland C3 supports a shrub community dominated by spiraea (Spiraea douglasii) growth with scattered willow shrubs. Hydrology is seasonal, with surface water probably drying up by early summer. Large woody debris from past logging activities is prevalent within the wetland. Wetland C3 does not contain significant amounts of organic soil. Cowardin Dominant Vegetation PALUSTRINE Spiraea douglasii Scrub-Shrub, Broad-Leafed Deciduous Salix lasiandra Seasonally Flooded, Fresh Salix sitchensis Organic/Mineral BOUNDARY DELINEATION The boundary of Wetland C3 is a generally distinct, topographic edge a couple feet above the basin bottom at the toe of the surrounding, descending slopes. All three parameters of soil, water (hydrology), and plants change abruptly along a fairly level gradient. The following table depicts general field indicators used to delineate the Wetland C3 boundary: WETLAND UPLAND Spiraea douglasii Pseudotsuga menziesii 1 chroma 3 chroma water in pit dry pit BOTH 2 chroma FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 3 0 4 1 Groundwater Recharge HIGH Significant seepage potential into adjacent well-drained soils during high water conditions. Sediment Capture HIGH Closed depression with no regular surface water outlet. Stormwater Detention HIGH Closed depression with no regular surface water outlet. Biofiltration LOW No emergent habitat; only seasonally-persistent surface water. Plant/Animal Habitat Value LOW Dense, monotypic spiraea; only seasonally-persistent surface water. Surface Water Runoff Route LOW Isolated basin with no regular surface water outlet. Surface Water Supply LOW Isolated basin with no regular surface water outlet. Flood Attenuation NA Not associated with a Riverine system. CATEGORY RATING: III (48 pts) Score for Water Quality Functions 16 Score for Hydrologic Functions 14 Score for Habitat Functions 18 TOTAL Score for Functions 48 GROUP – D WETLANDS SMALL, SCATTERED KETTLLES This grouping includes a total of 14 individual wetlands that occur as small, isolated systems. Thirteen of these wetlands occur scattered throughout the southwest portion of the property, while D14 occurs in the northeast corner. All systems are situated within their own, individual basin (primarily kettles), and support seasonal surface water conditions with either shrub or forested habitats. The smallest systems are only a few hundred square feet in size, with the largest ranging up to 28,737 square feet. Four of the wetlands are below the minimum jurisdictional size for regulation by the City of Yelm Critical Areas Ordinance. All of these wetlands are strictly isolated, and would never achieve a surface water outlet to Federally-regulated wetlands or streams. Due to the significant similarities between many of these systems, only 4 descriptions are provided. Two systems are described individually (D1 and D14), and the remaining are described in 2 sets of 6 wetlands each. WETLAND D1 SIZE: 28,737 sqft (0.66 Acre) LANDSCAPE POSITION Wetland D1 is a Depressional, Closed, very round, oval system set within a shallow kettle basin within a gentle rolling upland landscape. CLASSIFICATION Approximately 95% of Wetland D1 is dominated by tall, dense spiraea (Spiraea douglasii), with a perimeter of willow shrubs around the shallower edges. Very large logs ( debris from past logging activities ( occur scattered around this system. Hydrology is seasonal to semi-permanent, with surface water likely persisting well into summer of normal years. Wetland D1 occurs atop a formation of Mukilteo muck, surrounded by upland Alderwood soils. Cowardin Dominant Vegetation PALUSTRINE Spiraea douglasii Scrub-Shrub, Broad-Leafed Deciduous Salix lasiandra Seasonally to Semi-permanently Flooded, Fresh Organic BOUNDARY DELINEATION The Wetland D1 boundary is a fairly distinct, topographic edge that occurs near the top of the brief, abrupt slope descending to the wetland basin from the surrounding uplands. While soil and water (hydrology) characteristics change abruptly at the wetland/upland interface, some wetland vegetation extends into the upland condition. The following table depicts general field indicators used to delineate the Wetland D1 boundary: WETLAND UPLAND Carex obnupta Gaultheria shallon 1 chroma Muck soil 3 chroma Alderwood Soil water in pit dry pit BOTH Spiraea douglasii Salix lasiandra FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 2 2 3 1 Sediment Capture HIGH Isolated basin with no surface water outlet. Stormwater Detention HIGH Closed, depressional basin with many feet of storage capacity. Biofiltration MOD Possibly semi-permanent to permanent surface water with dense shrub growth. Plant/Animal Habitat Value MOD Monotypic habitat structure, but persistent surface water conditions should provide local drinking water source. Groundwater Recharge LOW Underlying, poorly-drained muck soils; surrounding uplands have glacial till. Surface Water Runoff Route LOW Isolated basin with no surface water outlet. Surface Water Supply LOW Isolated basin with no surface water outlet. Flood Attenuation NA Not associated with a Riverine system. CATEGORY RATING: III (42 pts) Score for Water Quality Functions 16 Score for Hydrologic Functions 12 Score for Habitat Functions 14 TOTAL Score for Functions 42 WETLANDS D2, D3, D4, D5, D6, D7 SIZE: D2 9,951 sqft (0.23 Acre) D3 3,214 sqft (0.07 Acre) D4 2,378 sqft (0.06 Acre) D5 2,958 sqft (0.07 Acre) D6 1,598 sqft (0.04 Acre) D7 2,302 sqft (0.05 Acre) LANDSCAPE POSITION All of the D2 through D7 group of wetlands are Depressional, Closed systems situated within small kettle basins that occur amid a gently rolling, upland landscape. CLASSIFICATION All of the D2 through D7 wetlands qualify as forested habitats due to the 20+ foot height of the willows (Salix sp.) that occur. All of these systems also support a dense, sometimes solid growth of shrubs dominated by spiraea first, and willow second. However, two of the wetlands have a high, closed tree canopy that inhibits solid shrub growth. These two systems have areas of bare ground or localized emergent vegetation, primarily water parsley (Oenanthe sarmentosa) or slough sedge (Carex obnupta). Hydrology is very seasonal, with shallow surface water probably persisting only into late spring in most systems. Large woody debris is common from past logging activities. None of the D2 through D7 wetland systems have mapped organic soils, but are shown to occur within upland formations of mineral soils. BOUNDARY DELINEATION Most of the wetland boundaries associated with the D2 through D7 group of wetlands are distinct, topographic edges near the toe of the descending slopes that surround each site. All three parameters of soil, water (hydrology), and plants change abruptly at the wetland/upland interface. The following table depicts general field indicators used to delineate this wetland boundary: WETLAND UPLAND Carex obnupta Gaultheria shallon 1 chroma 2 chroma w/out mottles water in pit dry pit BOTH Rubus spectabilis Mineral soils FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 2 0 6 1 Stormwater Detention HIGH Depressional basins with no surface water outlets and several feet of storage capacity. Groundwater Recharge LOW/HIGH HIGH for systems within well-drained Everett soils; LOW for systems in Alderwood soils with glacial till. Biofiltration LOW Limited, seasonal surface water persistence; generally poor emergent plant community. Plant/Animal Habitat Value LOW Very small size; minimal seasonal persistence of shallow surface water. Sediment Capture LOW Isolated basins with no surface water outlets. Surface Water Runoff Route LOW Isolated basins with no surface water outlets. Surface Water Supply LOW Isolated basins with no surface water outlets. Flood Attenuation NA Not associated with a Riverine system. D2 CATEGORY RATING: III (50 pts) Score for Water Quality Functions 16 Score for Hydrologic Functions 16 Score for Habitat Functions 18 TOTAL Score for Functions 50 D3 CATEGORY RATING: III (44 pts) Score for Water Quality Functions 16 Score for Hydrologic Functions 10 Score for Habitat Functions 18 TOTAL Score for Functions 44 D4 CATEGORY RATING: III (46 pts) Score for Water Quality Functions 16 Score for Hydrologic Functions 12 Score for Habitat Functions 18 TOTAL Score for Functions 46 D5 CATEGORY RATING: III (48 pts) Score for Water Quality Functions 16 Score for Hydrologic Functions 14 Score for Habitat Functions 18 TOTAL Score for Functions 48 D6 CATEGORY RATING: III (43 pts) Score for Water Quality Functions 16 Score for Hydrologic Functions 12 Score for Habitat Functions 15 TOTAL Score for Functions 43 D7 CATEGORY RATING: III (47 pts) Score for Water Quality Functions 16 Score for Hydrologic Functions 14 Score for Habitat Functions 17 TOTAL Score for Functions 47 WETLANDS D8, D9, D10, D11, D12, D13 SIZE: D8 1,558 sqft (0.04 Acre) D9 710 sqft (0.02 Acre) D10 960 sqft (0.02 Acre) D11 800 sqft (0.02 Acre) D12 313 sqft (0.01 Acre) D13 3,010 sqft (0.07 Acre) LANDSCAPE POSITION The D8 through D13 wetlands are all Depressional, Closed systems within very small, probably kettle basins. CLASSIFICATION All of these very small, generally oval wetlands support a shrub habitat class. Most have small woody debris pushed in them from past logging activities. Hydrology is very seasonal, shallow surface water that may not persist into late spring in normal years; all sites should be dry by July. Cowardin Dominant Vegetation PALUSTRINE Spiraea douglasii Scrub-Shrub, Broad-Leafed Deciduous Salix lasiandra Seasonally Flooded, Fresh Carex obnupta Mineral BOUNDARY DELINEATION Most of the boundaries on the D8 through D13 wetlands are fairly distinct, topographic edges around the bottoms of the depressions that support the systems. All three parameters of soil, water (hydrology), and plants change abruptly at the limit of saturation. The following table depicts general field indicators used to delineate this wetland boundary: WETLAND UPLAND Carex obnupta Polystichum munitum 1 chroma 3-4 chroma water in pit dry pit BOTH Rubus spectabilis Mineral soils FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 1-2 1 4-5 1 Sediment Capture HIGH Isolated basins with no surface water outlet. Stormwater Detention MOD Depressional structure but very small size limits capacity. Groundwater Recharge LOW/HIGH HIGH for systems within well-drained Everett soils; Low for systems in Alderwood soils with glacial till. Biofiltration LOW Short duration of shallow surface water, mostly during non-growing season. Plant/Animal Habitat Value LOW Small size; lack of persistent surface water; low structural diversity. Surface Water Runoff Route LOW Isolated depression with no surface water outlet. Surface Water Supply LOW Isolated depression with no surface water outlet. Flood Attenuation NA Not associated with a Riverine system. D8, D9, D10, D11, D12, D13 CATEGORY RATING: III (39pts) Score for Water Quality Functions 10 Score for Hydrologic Functions 12 Score for Habitat Functions 17 TOTAL Score for Functions 39 WETLAND D14 SIZE: 2,496 sqft (0.06 Acre) LANDSCAPE POSITION Wetland D14 is Depressional, closed system set within the lowest point of the surrounding, gently rolling landscape. CLASSIFICATION Wetland D14 supports a small thicket of Spiraea surrounding by mixed grasses. Hydrology consists primarily of saturated soils, with only temporary to seasonal surface water a few inches deep. Because the surrounding landscape consists of abandoned pasture devoid of trees, there is no woody debris within this wetland. Cowardin Dominant Vegetation PALUSTRINE Douglas' spiraea Scrub Shrub, Broad Leafed Deciduous Phalaris arundinacea Temporary to Seasonally Flooded, Fresh Mineral BOUNDARY DELINEATION The Wetland D14 boundary is very indistinct, and was based primarily on the presence of significant mottling plus oxidized rhizospheres along plant roots. The basin within which this wetland occurs is both shallow and lacks the abrupt, usually steep, surrounding slopes prevalent within the other Group D wetlands. The following table depicts general field indicators used to delineate the Wetland D14 boundary: WETLAND UPLAND Cytisus scoparius 2 chroma w/mottles Oxidized rhizospheres 3 chroma No oxidized rhizospheres BOTH Phalaris arundinacea Everett soils FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 1 2 4 1 Sediment Capture HIGH Isolated basin with no surface water outlet. Groundwater Recharge MOD Excessively drained Everett soils, but limited volume capacity. Stormwater Detention MOD Depressional basin, but very small size limit capacity. Biofiltration LOW Short duration of shallow surface water during non-growing season. Plant/Animal Habitat Value LOW Small size; lack of persistent surface water; low structural diversity. Surface Water Runoff Route LOW Isolated basin with no surface water outlet. Surface Water Supply LOW Isolated basin with no surface water outlet. Flood Attenuation NA Not associated with a Riverine system. CATEGORY RATING: IV (29 pts) Score for Water Quality Functions 12 Score for Hydrologic Functions 10 Score for Habitat Functions 7 TOTAL Score for Functions 29 GROUP – E WETLAND PERCHED CLUSTER One wetland with three associated parts is described for the Perched Cluster. SIZE: E1 13,219 sqft (0.30 Acre) E2 553 sqft (0.01 Acre) E3 1,895 sqft (0.04 Acre) LANDSCAPE POSITION The Perched Cluster wetland is a Depressional, Closed system perched within a shallow basin amid a nearly flat to gently rolling landscape. CLASSIFICATION Although three distinct basins make up the Perched Cluster wetland, the two small ones are close enough to the third, much larger basin to qualify them as a single, mosaic system. Shrubs dominate the plant community in the system, with mostly dense spiraea growth mixed with some rose (Rosa pisocarpa). Perimeter areas tend to have small red alder (Alnus rubra) or willow (Salix sp), and some growth of slough sedge (Carex obnupta) occurs where the shrub overstory is more open. Hydrology is seasonal, with the entire wetland dry at the time of the early August 2006 field review. Cowardin Dominant Vegetation PALUSTRINE Spiraea douglasii Scrub-Shrub, Broad-Leafed Deciduous Rosa pisocarpa Seasonally Flooded, Fresh Alnus rubra Mineral Salix sp. Carex obnupta BOUNDARY DELINEATION The Perched Cluster wetland boundary is clearly defined by a short, abrupt drop to the wetland basin from the surrounding, generally level landscape. All three parameters of soil, water (hydrology), and plants change abruptly near the top of this minor slope. The following table depicts general field indicators used to delineate this wetland boundary: WETLAND UPLAND Carex obnupta Pseudotsuga menziesii 1 chroma 4 chroma water marks no water marks BOTH Alderwood soil FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 2 0 5 1 Sediment Capture HIGH Isolated basin with no surface water outlet. Stormwater Detention HIGH Depressional basin without an outlet and at least 2 feet of storage. Biofiltration LOW Limited emergent vegetation; only seasonal, static surface water. Groundwater Recharge LOW Underlying Alderwood soils have a shallow till layer that inhibits vertical movement of water. Plant/Animal Habitat Value LOW Low structural diversity; only seasonally-persistent, shallow surface water. Surface Water Runoff Route LOW Isolated basin with no surface water outlet. Surface Water Supply LOW Isolated basin with no surface water outlet. Flood Attenuation NA Not associated with a Riverine system. CATEGORY RATING: III (43 pts) Score for Water Quality Functions 12 Score for Hydrologic Functions 14 Score for Habitat Functions 17 TOTAL Score for Functions 43 GROUP – F WETLAND LINEAR SWALE One wetland is described for the southwest outlet basin SIZE: 105,386 sqft (2.42 Acres) On site LANDSCAPE POSITION Wetland F is a combination of Slope and Depressional, Outflow structure. It occurs as linear, continuous swale winding through a gently rolling landscape. CLASSIFICATION The Wetland F system is a long, linear swale associated with hydric soil formations that snake through the landscape along very low-gradient troughs. Unlike any other wetland on the Thurston Highlands property, this system has its headwater beginnings well off-property to the south, and simply flows through the southeast property corner. Although significant volumes of flowing surface water occur within this system during wet periods in winter and early spring, the generally wide, fully vegetated trough does not develop technical stream conditions (no scour channel). The on- and near-property portions of this system support a deciduous forest habitat dominated by mostly tall willows (Salix sp.). A dense shrub layer also occurs, but emergent habitat is limited by shading from the nearly solid deciduous canopy. Hydrology is seasonal, and should persist into mid-summer in normal years. Cowardin Dominant Vegetation PALUSTRINE Salix sp. Forested, Broad-Leafed Deciduous Fraxinus latifolia Seasonally Flooded, Fresh Pseudotsuga menziesii Mineral BOUNDARY DELINEATION The Wetland F system has two very different boundary conditions. Along the west side, against a descending, steep slope, the wetland boundary is a very distinct topographic edge where all three parameters of soil, water (hydrology), and plants change abruptly at a couple feet above the trough bottom. However, along most other edges, adjacent upland ground has little to no slope, and the upland/wetland interface changes gradually across a generally wide area. Delineation here relied heavily on the presence of water in soil pits. The following table depicts general field indicators used to delineate the Wetland F boundary: WETLAND UPLAND Fraxinus latifolia Polystichum munitum 1 chroma 2.5+ chroma water in pit dry pit BOTH Tisch soils FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 2 3 3 0 Flood Attenuation HIGH Dense, woody vegetation within a wide swale of sheet-flowing water. Surface Water Runoff Route HIGH Major vicinity drainage route. Plant/Animal Habitat Value MOD Good structural diversity within forest and shrub communities. Stormwater Detention MOD Wide, depressional trough, but mostly unconstricted outlet. Surface Water Supply MOD Substantial, but only seasonal surface flows directed toward Thompson Creek. Biofiltration LOW Limited emergent cover; only seasonally-persistent surface water. Groundwater Recharge LOW Poorly-drained underlying soils. Sediment Capture LOW Limited emergent cover; no static surface water. CATEGORY RATING: II (53 pts) Score for Water Quality Functions 20 Score for Hydrologic Functions 14 Score for Habitat Functions 19 TOTAL Score for Functions 53 GROUP – G WETLANDS SLOPE BOTTOM BASINS The two small Group G wetlands are set within shallow basins at the bottom of steep, short slopes. They occur fairly close to one another in the east portion of the property. Neither of the wetlands would achieve an outfall that could reach federally regulated habitats. WETLAND G1and G2 SIZE: G1 22,413 sqft (0.52 Acre) G2 7,992 sqft (0.18 Acre) LANDSCAPE POSITION Both of the G group wetlands are Depressional, Closed systems set within shallow basins at the base of a steep slope. These wetlands have no potential for a surface water outlet connection to Federally-regulated waters. CLASSIFICATION These wetlands are both forested habitats, with G1 dominated by willow (Salix sp.) and G2 by aspen (Populus tremuloides.) Both have rather dense shrub canopies of mixed species. Hydrology consists of shallow, seasonal surface water that should only persist into late spring or early summer. Both wetlands occur within a large formation of Everett soils. Cowardin Dominant Vegetation PALUSTRINE Salix lasiandra Forested, Broad-Leafed Deciduous Populus tremuloides Seasonally Flooded, Fresh Spiraea douglasii Mineral Rosa pisocarpa Physocarpus capitatus Oenanthe sarmentosa BOUNDARY DELINEATION The wetland boundaries of the two G group systems are fairly distinct, topographic edges where all three parameters of soil, water and plants change abruptly along an elevation a couple feet above the basin bottom. The following table depicts general field indicators used to delineate the Wetland G1 and G2 boundaries: WETLAND UPLAND Spiraea douglasii Polystichum munitum 1 chroma 2 chroma water in pit dry pit BOTH Physocarpus capitatus Rosa pisocarpa 2 chroma Everett soils FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 1 2 4 1 Stormwater Detention HIGH Depressional basins with significant storage capacity and no regular surface water outlet. Groundwater Recharge MOD Underlying Everett soils are well-drained and lack an impervious till layer. Plant/Animal Habitat Value MOD Structurally diverse shrub and forest habitat; only seasonally-persistent surface water. Biofiltration LOW Limited emergent vegetation; only seasonally-persistent surface water. Sediment Capture LOW Isolated basin with no regular surface water outlet. Surface Water Runoff Route LOW Isolated basin with no regular surface water outlet. Surface Water Supply LOW Isolated basin with no regular surface water outlet. Flood Attenuation NA Not associated with a Riverine system. G1 and G2 CATEGORY RATING: III (44 pts) Score for Water Quality Functions 12 Score for Hydrologic Functions 14 Score for Habitat Functions 18 TOTAL Score for Functions 44 GROUP – H WETLANDS NORTHEAST DRAINAGE SYSTEM The H group wetland complex represents a single, large system with several individual “parts,” some of which have been artificially created and/or altered by past ditching and excavation. Originally, this wetland complex consisted of a large, oval, headwater basin with a single, narrow, linear arm connecting to the basin along a separate landscape trough. Where the oval basin and linear trough came together, the system then became a single, linear outlet swale that continued off-property. Earthwork alterations to the environment have now created a new, artificial outlet route and a small, oval pond. In addition, ditching significantly reduced the normal level of surface water persistence within the large basin, and has left the original, native outlet channel as an abandoned, dead-end swale that no longer has an upstream connection. All wetland conditions associated with this group have seasonal surface water outlet connections to Federally-regulated habitats. Three individual wetlands are described for this system. WETLAND H1 SIZE: 368,895 sqft (8.47 Acres) LANDSCAPE POSITION Wetland H1 is a Depressional, Outflow system that represents the headwater beginning to a continuous drainage route eventually connecting to Thompson Creek. CLASSIFICATION Wetland H1 has been drained in the past with a large, deep, centralized ditch that probably reduced persistent surface water levels by 2 to 3 feet. Existing conditions support a range of habitats, with emergent and shrub communities in the “lower” portions of the wetland, while forested conditions occur in the “upper” portions. Primary hydrology is saturated ground, with only temporary, shallow surface water during major storm events. Cowardin Dominant Vegetation PALUSTRINE Populus trichocarpa Forested, Broad-Leafed Deciduous Thuja plicata Scrub-Shrub, Broad-Leafed Deciduous Spiraea douglasii Saturated to Seasonally Flooded, Fresh Rosa pisocarpa Mineral Phalaris arundinacea Ditched Agrostis tenuis BOUNDARY DELINEATION Most of the Wetland H1 boundary is moderately distinct, but past drainage activities have created a fringe of “effectively drained” ground around the entire perimeter. Because of this condition, delineation was performed in March 2006 and relied heavily on the presence or absence of water or saturated soil within test pits. The southern, forested portion of the wetland contains a hummocky ground topography that translates into a mosaic condition where low spots are wetland and high ones are upland. Wetland H1 is primarily associated with a formation of hydric, McKenna soil. The following table depicts general field indicators used to delineate the Wetland H1 boundary: WETLAND UPLAND Carex obnupta Cytisus scoparius 2 chroma 3+ chroma water in pit dry pit BOTH FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 2 1 4 1 Plant/Animal Habitat Value HIGH Three habitat classes provide high structural diversity. Sediment Capture HIGH Dense emergent and shrub growth. Surface Water Runoff Route MOD Headwater beginning to minor tributary to Thompson Creek. Biofiltration LOW Minimal persistent surface water due to ditching. Groundwater Recharge LOW Underlying poorly drained soil; Minimal surface water persistence due to ditching. Stormwater Detention LOW Ditched outlet with no constriction. Surface Water Supply LOW Only seasonal surface water discharge. Flood Attenuation NA Not associated with a Riverine system. CATEGORY RATING: III (47 pts) Score for Water Quality Functions 10 Score for Hydrologic Functions 14 Score for Habitat Functions 23 TOTAL Score for Functions 47 WETLAND H2 SIZE: 23,824 sqft (0.55 Acre) LANDSCAPE POSITION Wetland H2 is a long, linear, shallow trough set within a gently rolling landscape. It is a Depressional, Outflow system that connects to the lower end of Wetland H1. CLASSIFICATION Wetland H2 supports a forested class with a minimum of shrub and ground canopies. Primary hydrology is saturated soil, but stormwater flows may be sustained during wet winters when groundwater is high and precipitation heavy. The ditching within Wetland H1 probably eliminated the occurrence of persistent, shallow surface water in Wetland H2, also. Technical wetland conditions fade away moving “uphill” along the swale, even though the swale continues on through the landscape in an upland condition. Cowardin Dominant Vegetation PALUSTRINE Populus trichocarpa Forested, Broad-Leafed Deciduous Fraxinus latifolia Saturated Soils, Fresh Thuja plicata Mineral Spiraea douglasii Rosa pisocarpa BOUNDARY DELINEATION The Wetland H2 boundary is fairly distinct along the lower end, being generally defined by an abrupt edge on the shallow trough within which the system occurs. However, at the “upper” end of the wetland where technical conditions begin to fade and the trough loses a distinct edge, delineation becomes problematic. Wetland boundaries at the upper end were mostly established based on the presence or absence of water in test pits. The following table depicts general field indicators used to delineate the Wetland H2 boundary: WETLAND UPLAND Polystichum munitum 1 chroma 2 chroma, no mottles saturated to surface dry pit BOTH Symphoricarpos albus Alnus rubra soils FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 0 1 6 1 Surface Water Runoff Route MOD May sustain persistent stormwater flows during wet winters. Biofiltration LOW Only temporary, shallow surface water during wet periods in winter. Groundwater Recharge LOW Lacks persistent shallow surface water. Plant/Animal Habitat Value LOW Lacks persistent shallow surface water. Sediment Capture LOW Sparse emergent ground cover. Stormwater Detention LOW Minimal depressional structure. Surface Water Supply LOW Primarily temporary surface water outlet during winter rains. Flood Attenuation NA Not associated with Riverine system. CATEGORY RATING: III (36 pts) Score for Water Quality Functions 7 Score for Hydrologic Functions 10 Score for Habitat Functions 19 TOTAL Score for Functions 36 WETLAND H3 SIZE: 82,514 sqft (1.89 Acres) LANDSCAPE POSITION: Wetland H3 has two, linear swales, one a natural, remnant surface water runoff route and the other an artificially excavated channel that connects to the ditch in Wetland H1. In addition, a small, oval pond has been constructed adjacent to the excavated channel. All three wetland portions qualify as Depressional, Outlet systems. CLASSIFICATION Wetland H3 represents the outlet drainage route for Wetland H1. The original, native outlet route is now an abandoned channel where the upper portion has been altered (filled in) by past earthwork. An artificial channel was excavated to replace the abandoned channel, probably in association with the ditching of Wetland H1. Both swales support a mixture of shrub and emergent communities across their width, with a margin of mostly tall trees that create a closed canopy overhead. The abandoned channel now supports pockets of shallow surface water while the artificial channel sustains seasonal, shallow sheet-flow draining from Wetland H1. The small pond is a permanent water feature that varies significantly in depth from winter to summer. Where the two swale portions of Wetland H3 connect, the system then turns into a Category I Mature Forested condition that continues to the east property line dominated by large black cottonwood and Oregon ash trees. North of the Thurston Highlands property, the wetland occurs as an actively grazed, cleared emergent pasture dominated by a saturated soil hydrology. Cowardin Dominant Vegetation PALUSTRINE Fraxinus latifolia Forested, Broad-Leafed Deciduous Populus trichocarpa Emergent, Persistent Physocarpus capitatus Saturated to Seasonally Flooded, Fresh Symphoricarpos albus Mineral Ranunculus repens Oenanthe sarmentosa Graminoid spp. BOUNDARY DELINEATION All wetland edges associated with the Wetland H3 system are distinct boundaries generally identified by a brief, abrupt rise from the generally level swale bottom into the adjacent upland landscape. The following table depicts general field indicators used to delineate this wetland boundary: WETLAND UPLAND Oenanthe sarmentosa Polystichum munitum 1 chroma 2+ chroma saturated to surface dry pit BOTH Fraxinus latifolia Symphoricarpos albus Physocarpus capitatus FUNCTION ASSESSMENT Following is a list of commonly recognized wetland functions, with an estimated relative value rating for this wetland and a brief conceptual statement regarding the primary factor affecting this rating. A summary table is also provided for quick reference. HIGH MODERATE LOW NOT APPLICABLE 2 2 3 1 Plant/Animal Habitat Value HIGH Diverse plant community with emergent, shrub and forest species. Surface Water Runoff Route HIGH Outlet for Wetland H1; continuous drainage eventually connecting to Thompson Creek. Biofiltration MOD Shallow, sheet-flowing surface water through mostly dense emergent growth. Sediment Capture MOD Mostly dense emergent growth with shallow, sheet-flowing surface water. Surface Water Supply LOW Only seasonal surface water outlet. Groundwater Recharge LOW Minimal, persistent, non-flowing surface water. Stormwater Detention LOW Minimal depressional structure. Flood Attenuation NA Not associated with a Riverine system. CATEGORY RATING: I/III (40 pts) Category I: Mature forest at East property line. Score for Water Quality Functions 9 Score for Hydrologic Functions 10 Score for Habitat Functions 21 TOTAL Score for Functions 40 APPENDIX II: SOIL DATA SHEETS WETLANDS INVENTORY, WETLAND IMPACTS AND MITIGATION RECOMMENDATIONS FOR THE THURSTON HIGHLANDS MASTER PLANNED COMMUNITY JULY 2007 APPENDIX III: CATEGORY RATING FORMS WETLANDS INVENTORY, WETLAND IMPACTS AND MITIGATION RECOMMENDATIONS FOR THE THURSTON HIGHLANDS MASTER PLANNED COMMUNITY JULY 2007 REFERENCES Bloom, Doug. Partner, Thurston Highlands, L.L.C. May 29, 2007. Personal communication with Vicki Morris, Vicki Morris Consultant Services (EIS author), re: the phased clearing and grading proposal for the Thurston Highlands Master Planned Community site. Cooke, Sarah Spear. Editor. 1997. A Field Guide to the Common Wetland Plants of Western Washington & Northwestern Oregon. Seattle Audubon Society, Seattle, WA. Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979, Reprinted 1992. Classification of Wetlands and Deepwater Habitats of the United States. U.S. Fish and Wildlife Service, FWS/OBS-79/31, 103 pp. Environmental Laboratory. 1987. Corps of Engineers Wetland Delineation Manual, Technical Report Y-87-1, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS. Federal Interagency Committee for Wetland Delineation. 1989. Federal Manual for Identifying and Delineating Jurisdictional Wetlands. U.S. Army Corps of Engineers, U.S. Environmental Protection Agency, U.S. Fish and Wildlife Service, and U.S.D.A. Soil Conservation Service, Washington, D.C. Cooperative technical publication. 76 pp. plus appendices. Hitchcock, C.I., and A. Cronquist. 1976. Flora of the Pacific Northwest. University of Washington Press, Seattle, WA. Kollmorgen Corporation . 1992. Munsell Soil Color Charts. Baltimore, MD. KPFF. 2007. The Thurston Highlands Drainage and Utility Technical Engineering Report Reed, P.B. Jr. 1988. National List of Plant Species that Occur in Wetlands: National Summary. USFWS Biological report 88(24). 244 pp. Reed, P.B. Jr. 1993. Northwest Region 9, Supplement to National List of Plant Species that Occur in Wetlands: USFWS. U.S. Army Corps of Engineers. 1987. Corps of Engineers Wetland Delineation Manual. Technical Report Y-87-1, together with clarification and interpretation guidelines as published by the USACOE, 1992. U.S. Department of Agriculture, Soil Conservation Service. 1990. Soil Survey of Thurston County, Washington. USDA Soil Conservation Service. 283 pp. U.S. Department of Agriculture. 1991. Hydric Soils of the United States. Washington Department of Ecology. 1997. Washington State Wetland Identification and Delineation Manual. Publication #96-94. Washington Department of Ecology. 2004. Washington State Wetlands Rating System for Western Washington Revised. Publication #04-06-025. U.S. Department of the Interior. Circa 1987 ( 1989. National Wetlands Inventory Maps. Washington Department of Fisheries. 1975. A Catalog of Washington Streams and Salmon Utilization, Volume 1 and Volume 2. Yelm, City of. 2006. Yelm Municipal Code. Chapter 14.08 Critical Areas and Resource Lands.