About the Project
In March 2014, Caltrans established the Last Chance Grade Partnership to create an active, working relationship with the agencies and groups that have management responsibilities for lands and resources that would be directly impacted by any realignment of Highway 101 at Last Chance Grade.
Engineered Feasibility Study
The Partnership initiated an Engineered Feasibility Study (EFS) to identify potential improvement projects that can ensure the safety and reliability of the highway while protecting the area’s critical economic, environmental and cultural resources. The study is a detailed investigation that considers a full range of needs, options, ideas, opportunities, and constraints. The EFS is used as a reference document that identifies potential improvement projects, enabling Caltrans to respond to and compete for various project funding sources as they become available. The Engineered Feasibility Study was completed in 2015 and the entire study is available in the Document Library.
Project Study Report
The next step in the process was to develop the Project Study Report. This report performs a more detailed analysis of the alternatives recommended for further study in the EFS as they relate to the cost, scope, and schedule of developing the project. During this study, alternatives and alignments were refined with more precise cost estimates along with more detailed technical analysis of proposed structures and right-of-way. The Project Study Report was completed in 2016 and the entire report is available in the Document Library.
Preliminary Geotechnical Evaluations
In May of 2017, Caltrans received approval to fund $5 Million to perform preliminary geotechnical investigations. This effort will provide critical information on the subsurface conditions under the six build alternatives. Environmental documents and permits will be needed before field investigations can be conducted. Caltrans will also perform some environmental studies that relate to the environmental viability of project alternatives. Tree surveys will be performed in select locations to provide estimates of impacts to old growth redwoods. Caltrans and its Partners could ultimately make adjustments to the project alternatives or even eliminate alternatives based on information provided by the geotechnical investigations and tree surveys.
Expert Risk Assessment
Although a permanent realignment project remains unapproved and unfunded, Caltrans and the Federal Highway Administration (FHWA) began coordinating an Expert Risk Assessment in the spring of 2017. The Expert Risk Assessment will inform and support any recommendation to approve and fund a full realignment project. A team of subject matter experts will be assembled to study the practicality of maintaining a resilient and open highway at the current location for an extended period of time. The team will also consider the risks associated with staying on the current alignment and the risks associated with realigning the highway.
Storm Damage Repair
Caltrans continues efforts to maintain and repair the highway at Last Chance Grade. Heavy rains in March 2016, and later in the winter of 2017, resulted in multiple storm damage issues including cracks and settling on the roadway, deformation of retaining walls, and a localized landslide that resulted in the temporary loss of the southbound lane at postmile 14.4. In April 2017, the FHWA approved funding of $27.6M in construction dollars to repair this storm damage. The scope of work includes repairs to four retaining walls and new construction of or extensions to four additional retaining walls. Construction crews will also improve vertical settling to smooth out the ride. This repair work will begin in the summer of 2017, using emergency contracts. Work will also continue for the two retaining walls that have been in construction since 2016.
Geological Factors
Last Chance Grade is in an area prone to geological activity. In 2000, the California Geological Survey mapped over 200 active slides in the area.
More recently, surface monitoring data shows slow but steady movement of the roadway along the northern and southern sections of Last Chance Grade. The effects of this movement can be seen in existing retaining walls.
Landslides occur 1-3 times per decade; storm events in March 2011 and March 2012 resulted in significant roadway damage requiring emergency repairs. Storm damage in 2017 resulted in a temporary loss of the southbound lane at postmile 14.4.
Economic Factors
Highway 101 provides year-round access for commercial trucking and recreational traffic. Since 1980, landslide mitigation projects have cost over $67 million.
If Highway 101 is closed due to a major landslide, this vital connection would be broken and the costs would be felt throughout the area; residents, travelers and area businesses would be disrupted.
To quantify these impacts, Caltrans published an Economic Impact Study examining current costs and analyzing potential effects of an extensive closure of Highway 101. The entire report, completed in January 2015, is available in the Document Library.
A closure of Highway 101, caused by a landslide, could mean:
- $1.3 million per day in travel costs for commercial and passenger vehicles—$450 million each year
- $300-$400 million in reduced output in Del Norte County
- 3,000–4,000 jobs lost each year
- $130 million in lost wages annually
Cultural and Environmental Factors
The Del Norte Coast is a unique coastal ecosystem that is home to old-growth redwoods as well as rare and threatened animal species. The Del Norte Coast Redwoods State Park encompasses a majority of the affected highway.
The area was designated an International Biosphere Reserve by the United Nations in 1983.
The southern portion of Last Chance Grade intersects with an area of cultural significance, designated as a UNESCO World Heritage Site.
The area is of particular importance to the Yurok People, a Native American tribe that has maintained a presence in the region for centuries.
The UNESCO website describes the cultural significance of this site:
“Archaeological surveys, test excavations, research and consultations conducted over the past 20 years have resulted in the recording of 50 prehistoric archaeological sites, 19 historic sites and at least 21 places of significance to local Indian communities. The archaeological sites span 4,500 years and represent changing settlement and subsistence systems. Historic resources include examples of early trails, homestead and ranching, fishing, dairy, mining and logging industries, and military structure.”
Caltrans Projects at Last Chance Grade
Completed Projects
Soldier Pile Wall
This Emergency Opening project located near post mile 15.3 is designed to slow the movement of a slipout within the larger Last Chance Grade slide complex, to protect an existing wall completed in 2010 from further damage, and to reduce the frequency of repairs and delays to the traveling public. This $4.8 million (budgeted) project was completed in November 2013. The project included drilling 27 piles at a maximum depth of 80 feet for a soldier pile ground anchor wall, reconstructing portions of the roadway surface, and repairing drainage facilities damaged by the slipout. The contractor working on the Emergency Opening project was CalEx Engineering Company.
Emergency Soil Nail Project
An Emergency Soil Nail project at post mile 15.0 was completed in spring 2012.
Current and Future Projects
Slipout Repair at Post Mile 15.1
As a result of the March 2011 Federally Declared Storm Event, a slipout occurred that resulted in the failure of a portion of roadway shoulder, and loss of embankment fill below the roadway. The repair at this location will consist of construction of a soil nail wall. Construction began in summer 2016 and will continue through the 2017 season.
Restoration of Shoulder Width at Post Mile 15.0
The location of this project is the same location where a soil nail wall was constructed to prevent loss of the roadway in 2012. The purpose of this project is to regain roadway shoulder width that was lost during the March 2012 storms. This will be accomplished through construction of a Soldier Pile Ground Anchor Wall in front of the soil nail wall that was constructed in 2012. Construction began in 2016 and will continue through the 2017 season.
Storm Damage Repair from March 2016 and Winter of 2017
Heavy rains in March 2016 and later in the winter of 2017 resulted in multiple storm damage issues including cracks and settling on the roadway, deformation of retaining walls, and a localized landslide that resulted in the temporary loss of the southbound lane at postmile 14.4. In April 2017, the FHWA approved funding of $27.6M in construction dollars to repair this storm damage. The scope of work includes repairs to four retaining walls and new construction of or extensions to four additional retaining walls. Construction crews will also improve vertical settling to smooth out the ride. This repair work will begin in the summer of 2017 using emergency contracts.
