Project Overview
In response to repeated road washouts, the San Juan County Conservation Land Bank retained a consultant in 2021 to evaluate the gravel road/trail network on its 1,600-acre Turtleback Mountain Preserve on Orcas Island. The consultant developed plans for the replacement or addition of multiple culverts to improve conveyance in cross drains and intermittent, non-fish bearing streams and to ensure compliance with Washington State forest road requirements (WAC 222-24-0511). In preparation for the installation of nineteen road culverts, the Land Bank secured approval from Washington DNR under WAC 222-16 050(3) and contracted a cultural resources assessment in the work areas.
The Conservation Land Bank will implement temporary trail closures at the Preserve during June and July to accommodate the project. While we will make every effort to minimize disruptions, please expect temporary parking lot and trail closures to ensure public safety. Although the schedule is subject to change, we anticipate closing segments of the North Entrance trails for three to four weeks beginning June 26 and the South Entrance for up to one week beginning in mid-July.
Construction Details
The general work area is shown on Map 1 and culvert locations are shown on Maps 2-5 and described in Table 1. Contractor will procure the 18’ to 30” diameter HDPE culverts described in Table 2 as well as all necessary rock and gravel as described in the Project Plans and Fee Schedule, which are included here.
Culvert installation will follow three general approaches reflecting site conditions. Type 1 and 2 culverts are for ditch relief and small, low energy stream crossings, respectively. Type 3 crossings involve a greater level of excavation and additional inlet and outlet protection. Except for the following notes, details in the Project Plans prevail.
Appropriate native fill may be used in bedding in backfill. However, to ensure adequate availability of appropriate bedding and backfill material, Contractor will provide gravel as needed at the unit price in the Fee Schedule up to the not-to-exceed total. In cases where native fill material is inadequate to restore the road surface to drivable and walkable conditions, Contractor will spread and compact additional surface aggregate. The combination of native excavated material and the estimated gravel per culvert referenced in the Fee Schedule will be adequate for this purpose at all North Entrance culverts and for all but two South Entrance culverts. For Tier 2 Culverts S1 and S3, on Wild Rose Lane, Contractor will restore subgrade and gravel surface to pre-project conditions.
If Contractor must excavate rock (defined here as solid beds or masses in original or stratified position which can be removed only by the use of hydraulic or pneumatic tools, and all boulders of 1/3 of a cubic yard or more in volume rock that cannot be excavated), Contractor will bill for rock excavation at the unit price in the Fee Schedule up to the not-to-exceed total. Explosive materials used for blasting operations are not allowed on site. Rock excavated that cannot be incorporated into the backfill material as specified will be used for inlet or outlet protection or spread along the road shoulder and replaced with the quantity of acceptable material for backfilling. All other unnecessary excavated material will be spread in the work areas to match surrounding grades.
Contractor will haul and dispose of old culverts in an approved location. If additional culverts are required to meet installation specifications, Land Bank may provide the additional culverts. If the Land Bank is unable to procure the necessary culverts in a timely manner, Land Bank will compensate Contractor for additional culverts at cost plus ten (10) percent.
Following completion of ground disturbing activities, the Land Bank will stabilize all exposed soil with native seed and weed free straw as needed.
Trail Closures and Staging
Contractor will minimize the extent and duration of trail closures and will work with Land Bank staff to close trails or trail segments as necessary to enable construction. If operations cease for two days or more, Contractor will endeavor to secure work areas and reestablish trail access until work commences. As necessary for mobilization and demobilization purposes and to prevent unauthorized traffic, Contractor may close the North and South parking lots temporarily to the public. Contractor may stage equipment and materials at existing, level roadside turnouts along the North Entrance road system. Near the South Entrance, Contractor may stage equipment and materials at an existing, level roadside turnout along Wild Rose Lane or in the seasonal lot.