City of Liberty Lake – Henry Road Overpass & Roadway Extension

Nestled between Spokane Valley and the Idaho State border, the City of Liberty Lake is a master-planned community with a projected build-out population of 18,708 in 2042. The city is bisected by I-90, which runs east to west, and Harvard Road (Liberty Lake Road), which runs north to south. An additional north-south corridor would create better connectivity for residents, allow access to undeveloped areas within city limits, provide an alternate north-south route in case of emergency, and improve emergency response times throughout the city. The City of Liberty Lake has initiated a project to extend Henry Road—a two-lane complete street from Country Vista Drive on the city’s southside to Mission Avenue on the northside. The City of Liberty Lake, Spokane County, and Washington Department of Transportation (WSDOT) are funding the project with the city contributing $6 million. The City of Liberty Lake has hired Lochner to lead design.

The south terminus of the project begins where the existing Henry Road intersects with Country Vista Drive. Here, a new signalized intersection will be constructed as part of the project, and the existing Henry Road will be realigned and extended north. The design includes a two-lane roadway with a bike lane on both sides and a sixfoot-wide sidewalk on the east side. A ten-foot-wide shared use path will be added to the corridor’s west side to accommodate the city’s allowance of golf carts.

The project will construct on overpass where Henry Road meets I-90, which is adjacent to a Spokane County right of way corridor designated for future transit development. Interlocal agreements between the City of Liberty Lake, WSDOT, and Spokane County have been established and the overpass design is required to accommodate Henry Road and provide access to the future transit development. As a result, the Lochner team conducted a type, size, and location study to determine the most cost-effective and efficient design. The concepts considered were a single-span or a two-span overpass with four lanes divided by a median and a separate culvert structure for the future transit line or a three-span structure that would accommodate four lanes of traffic and the Spokane County right of way. Lochner’s design uses the three-span structure solution because it allows the most flexibility for the Spokane County right of way and provides costs benefits for the city.

On the north end of the project, Henry Road will tie into Mission Avenue with a four-leg, single-lane roundabout. A heavy construction equipment facility is being built nearby, so the design team adjusted the roundabout’s geometry, including lowering the standard truck apron by one inch, to meet the facility’s traffic needs. The roundabout will also provide access to planned residential developments to the north and west.

Although the project is not federally funded, the preparation and approval of a NEPA document is required as a pier of the Henry Road overpass will be constructed in the I-90 right of way. Lochner conducted a noise analysis and air quality hot spot analysis as part of the NEPA process. Additional design challenges include relocating a 14-inch water line and raising the grade of overhead transmission and distribution power lines that parallel I-90. The Lochner team is also working closely with the Department of Ecology to mitigate stormwater impacts that could potentially affect a pollution plume from a closed county landfill site located south of the project.

Agency coordination has been a critical element of the project. While the City of Liberty Lake is overseeing design as well as the project’s landscaping and irrigation, WSDOT will oversee construction. Lochner is working closely with representatives from both agencies as well as Spokane County to receive approval in a timely manner and maintain the project’s accelerated schedule. Lochner is also preparing two sets of design plans for the agencies to carry forward for construction.