East Lake Sammamish

View of Lake Sammamish from the North Segment of the East Lake Sammamish Trail

On the design plan sheets, located along the trail centerline are station numbers that look like “247+00, 248+00, 249+00, etc.” These numbers are unique identification numbers, measured in hundred foot increments. Each station number represents a specific location along the trail corridor. The numbers are typically used by King County staff, project engineers, and the construction contractor, but are also useful in communicating locations with adjacent property owners.

No. Safety and accessibility for all trail users are the County's top priorities. As a public agency, King County plans its facilities to benefit its citizens based on current and projected demand on its Regional Trail System.  The trail is designed to regional and national trail safety standards, as defined by the American Association of State Highway and Transportation Officials (AASHTO) and  Policy on Geometric Design of Highways and Streets, 2011 (Green Book). These standards were used in calculating the width required to ensure the trail has the capacity to safely accommodate users of all ages and abilities.

No. There are a number of factors that determined the trail alignment, including building the trail within a narrow corridor, and steep terrain. The County has designed the trail alignment by balancing the following considerations:

• Complying with local, state and federal environmental regulations to avoid and minimize impacts to environmentally sensitive areas
• Staying within the King County trail corridor
• Building a safe trail by adhering to the standards and guidelines in the American Association of State Highway and Transportation Officials (AASHTO) and Policy on Geometric Design of Highways and Streets, 2011 (Green Book)
• Minimizing costs where possible without impacting trail standards
• Minimizing impacts to adjacent homeowners
• Preserving significant trees

Examples of existing conditions along South Sammamish Segment B

Trail safety is King County’s top priority. Due to the extensive scope of work within the narrow trail corridor and the limited trail access, the trail will be closed to the public during construction. Closing the trail allows the County’s contractor to engage in multiple activities concurrently, which will result in an efficient and expeditious construction schedule. Completing this critical project quickly and safely will minimize impacts to trail users and adjacent property owners. 

Constructing the trail is challenging and difficult due to the narrow corridor, limited trail access, and steep topography. Additionally there are seasonal constraints on construction near streams, construction of retaining walls, mitigation and landscape planting and redevelopment of the intersections. The South Sammamish B segment is particularly challenging due to the close proximity to adjacent private property and the large number of intersecting driveways and property access points along the trail.

Construction crews working on a closed portion of the East Lake Sammamish Trail

King County is committed to a trail design that has minimal impacts to adjacent property owners though parking spaces may be reconfigured. Private parking is not ordinarily permitted on Parks property. However, after trail construction, an adjacent homeowner may contact King County Parks about obtaining a Special Use Permit. Such requests will be approved only in limited circumstances (e.g., where parking does not obstruct park users or emergency vehicles). 

The trail design for South Sammamish A and South Sammamish B does not include narrowing Sammamish Shore Lane. The depth of existing nose-in parking will be reduced in some places in South Sammamish B. This area may also function as a turnaround location for delivery trucks and emergency vehicles. The design plans are submitted to Eastside Fire and Rescue for their review and approval to ensure the project meets the emergency access needs.

Safety is King County’s highest priority. Intersections are designed to allow trail users and vehicles crossing the trail to clearly see one another. Sight distance triangles for the East Lake Sammamish Trail are calculated from the perspective of the intersecting vehicle. Vehicle sight distances are based on national standards outlined by AASHTO in A Policy on Geometric Design of Highways and Streets, 2011 (Green Book). A detailed explanation of how King County determines site distance triangles and why other standards are not used is available for review or download on the project website: www.kingcounty.gov/eastlakesammamishtrail, under South Sammamish A or South Sammamish B / Project Guides / Sight Distance Triangles. 

Example of of poor sight triangles at and intersection vs. improved sight triangles at an intersection

To construct the wider trail, removal of some vegetation is unavoidable.  Clearing beyond the edge of the existing trail is necessary to construct the new trail, retaining walls, drainage improvements and environmental features. The trail design includes new landscaping and restoration of areas disturbed during construction. All vegetation removal will be within the ELST trail corridor.

The trail will feature native plants, shrubs, and trees to restore the project area and achieve the following goals and objectives:

 • Open sightlines at road and driveway crossings to improve safety by planting the area within the sight triangles with plants that grow less than three feet high at full maturity. 

Examples of landscaping along the East Lake Sammamish Trail

The new landscaping will consist of a variety of small, medium and large native plants and trees. The team carefully selected native trees and shrubs planted along the trail corridor in addition to the meticulous placement of logs, rocks, snags and brush piles result in scenic views and wildlife friendly features. Plant diversity provides food for a variety of wildlife while structural diversity provides wildlife shelter from summer and winter weather.

The new trail is being constructed entirely within King County’s trail corridor. Constructing a wider trail that is safe for users of all ages and abilities will require removing some landscaping and other items such as fencing that are currently encroaching on the County’s trail corridor and that will impact trail construction. Prior to the start of construction, King County will notify adjacent property owners and provide an opportunity to remove and relocate the encroaching items to their property.

South Sammamish Segment B- in this 3.6-mile segment, approximately 275 significant trees are planned for removal. King County will apply the same approach to South Sammamish Segment B as was applied in all of the other trail segments. King County is proposing to plant over 1,400 trees, 8,500 taller shrubs, and 14,000 lower shrubs and plants, including the planting of approximately 3.25 acres of wetland, wetland and stream buffer, and shoreline setback area, improving and creating new wildlife habitats.

Examples of fish culverts along the East Lake Sammamish Trail

• Wetlands are regulated, not only by the City, but also the U.S. Army Corps of Engineers  (the Corps) and Washington Department of Ecology (Ecology). When these features are delineated, approved methodologies by the Corps and Ecology are used (consistent with City requirements)—with a focus on the three criteria of vegetation, soils, and hydrology (inundation or soil saturation near the surface).
• Jurisdictional ditches are features that do not meet the criteria for wetland, but they are hydrologically connected to surface waters (waters of the US). The Corps also regulates jurisdictional ditches.
• The City, Ecology, and the Corps have a wetland mitigation sequencing that starts with avoidance and then minimization before moving to compensatory mitigation. Based upon input received from the City and adjacent homeowners, the County used the following approach in developing a mitigation strategy for ELST; 
  • Impact wetland buffers closest to the trail in order to protect trees and screening vegetation on the west side of the trail (water side).  This approach and as part of the review process with the City, the compensatory buffer mitigation will occur onsite— adding buffer to existing regulated buffer areas at approximately  1:1 ratio and enhancing existing regulated buffer at approximately 1:1 ratio. 
  • Avoid any wetland fill. Although many of the wetlands are a lower class of wetland, they are still providing important functions such as regulating water quantity and improving water quality. Additionally, the Corps and Ecology require compensatory mitigation for wetland fill to meet higher ratios, requiring more land for mitigation in an already tightly constrained area.
  • Avoid other jurisdictional ditches. The vegetation in these ditches slows and filters the water that flows through them. Because of space constraints, relocating and replacing the jurisdictional ditches in kind is not possible.

Trail safety is a top priority for King County. The new trail has been designed to meet all applicable engineering and safety standards. The trail design clearly identifies intersections with consistent signage, striping, and bollards. Safety design features include:

• Providing open sightlines for trail users, motorists, and pedestrians crossing the trail;
• Provides a visual and textural difference from the asphalt trail by constructing concrete intersections;
• Warning trail users of approaching intersections with textured concrete warning bands 75 feet ahead of each crossing;
• Identifying intersections clearly through consistent signage, striping, and bollards. 

View of an improved intersection from the North Segment of the East Lake Sammamish Trail

Funding for the ELST South Sammamish Segment B is provided by the 2014-2019, voter-approved Parks, Open Space and Trails Levy and the 2020-2025, voter-approved Parks, Open Space and Trails Levy.