In this issue:
- Guide offers local engineers cost-effective methods for slope stabilization
- Report outlines feasibility of unified permitting
- Prefabricated bridge reduces costs and environmental impact
- Report offers snow removal performance metrics
- Minnesota & Nebraska LTAPs partner to deliver motor-grader training
In a recent project, University of Minnesota Duluth (UMD) researchers determined effective methods for stabilizing slopes along Minnesota’s locally maintained roads and created a guide recommending slope stabilization methods for common site types. Previously, there was no guide for public works engineers to stabilize slopes of the scale typically seen along locally maintained roadways.
“While no single method is appropriate for all situations, several methods have proven effective, and our guidebook succinctly summarizes those methods for local government engineers,” says David Saftner, an associate professor in UMD’s Department of Civil Engineering.
The guide begins with an overview of the common causes of slope failure and methods of stabilizing slopes. Next, eight different slope failure scenarios are presented. Descriptions of these scenarios include a summary of site conditions at each slope failure and recommended solutions to repair the failure. Following these descriptions are recommended resources that provide more information about each of the stabilization methods.
Ultimately, this study and guide address the need for a consistent, logical approach to slope stabilization founded in research and experience. “Our guide was developed using resources not typically available to all county engineering and maintenance departments such as soils lab testing, advanced modeling, and geotechnical analysis,” Saftner says. “By implementing these recommendations, local government engineers can improve the stability of roadway embankments, minimize slope failure and associated damage, and decrease preventive maintenance costs.”
The Minnesota Local Road Research Board funded the project.
- Slope Stabilization Guide for Minnesota Local Government Engineers (MN/RC 2017-17G, June 2017, 5.1 MB PDF)
- Technical summary: Field Guide Helps Local Engineers Stabilize Damaged Slopes (MN/RC 2017-17TS, Sept. 2017, 1.4 MB PDF)
- Final report: Slope Stabilization and Repair Solutions for Local Government Engineers (MN/RC 2017-17, June 2017)
Multiple jurisdictions within Minnesota process oversize/overweight (OSOW) permits for the movement of freight on state roadways, county roads, and municipal and township streets. A new report outlines the feasibility of implementing an OSOW unified permitting process that would allow a “one-stop-shop” for haulers and permitting agencies.
Movement of freight has increased in recent years to help support economic trends and construction needs. These moves often require haulers to offload from state roadways onto the county or municipal and township roadways for final delivery, causing pinch points (i.e., construction, vertical clearance issues, etc.) that may negatively impact the forecast life cycles of both roads and bridges. With haulers moving across roadway authorities, there is a desire to develop a unified process to support OSOW permits.
This research study, sponsored by MnDOT, examined the feasibility of implementing a one-stop-shop permitting software program to better support a unified permitting process. Project methodologies included reviewing current practices and developing a plan for creating a process, policies, and technologies to meet both local government and hauler needs.
The final report discusses the potential policy, process, and technology recommendations that can be tested for further implementation in future phases of the unified permitting process.
- Final Report: Oversize/Overweight Vehicle Unified Permitting Process (UPP) Phase I (MN/RC 2017-26, Aug. 2017, 4.2 MB PDF)
Thurston County, Washington, replaced a failed and aging culvert with a prefabricated bridge. The Beaver Creek bridge was fabricated offsite in units sized for placement in the environmentally sensitive area with a small crane and delivered to the work zone for installation. The county estimates that prefabrication reduced project costs by 50 percent over traditional construction methods.
The bridge installation drew national attention as a test case for construction activities within endangered species habitat. Breeding seasons for coho salmon and other native fish limit in-water construction work to a window between June and mid-September. The presence of endangered species also meant construction crews had a limited timeframe and limited space to accommodate construction activities. Yet despite the logistical issues, the project was successfully completed in less than one month, with minimal residential and traffic disruptions.
“This project not only shows that construction activities can be successfully accomplished in highly-sensitive habitat areas, but these bridges can reduce construction delays because they can be installed quickly and more efficiently than traditional methods,” said Matt Unzelman, project manager and senior civil engineer for Thurston County Public Works.
Prefabricated bridges are one of the innovations in Every Day Counts round 2 (EDC-2).
- Every Day Counts: Prefabricated Bridge Elements and Systems
- Thurston County, Washington, news release about the Beaver Creek project
Transportation agencies measure their snow removal success in some way or another, but measures are often inconsistent—one agency’s clear-pavement standard may not match another’s. It’s also difficult to determine if existing measures are accurately assessing the success of winter maintenance programs. Clear Roads investigators surveyed more than 50 local, state, and international transportation agencies to better understand snow removal performance metrics in use and under consideration.
The project’s goal was to catalog the range of winter maintenance performance measures that agencies use, especially newer outcome-based measures that may not have been captured in earlier research, and identify the most effective metrics.
The research team conducted a literature review and then sent surveys to U.S. and international agencies and private firms. The survey showed that outcome-based metrics have eclipsed traditional input- or output-based measures that focus on resources used.
More than 70 percent of agencies reported using outcome-based level-of-service (LOS) goals for road conditions or usage, with performance usually measured in terms of time required to achieve established LOS criteria. Maintaining safe and passable roads throughout storms, providing bare pavement as quickly as possible, and achieving specific traffic volumes were the most widely used LOS goals. Metrics included “bare pavement time,” a measure of how long it takes to reach an observable level of uncovered pavement, and “speed recovery time,” a measure of how long it takes driving speeds to return to normal following a storm.
- Two-page brief: Outcome-Based Performance Measures Provide Meaningful Data (July 2017, 856 KB PDF)
- Final report: Snow Removal Performance Metrics (May 2017, 1.9 MB PDF)
Minnesota LTAP partnered with Nebraska LTAP this summer to provide a two-day training course for motor-grader operators at four sites in Greater Minnesota. The course is typical of the innovative approach LTAP uses to provide local transportation agencies with essential training in the most effective, cost-efficient way.
"We’re continually looking for new ways to better meet the training needs of local agencies," says Mindy Carlson, Minnesota LTAP program manager. "This workshop is a great example of partnering with other LTAPs to share expertise and resources to the benefit of our local agencies, their staff, and the public they serve."
The training consists of one day in a classroom setting, then another day in a field setting on a local gravel road, with each workshop participant given a hands-on opportunity in a motor grader.
“We try to cover all basics that a maintenance operator has to face,” says course instructor Brian Jackson of Nebraska LTAP. “One of the things that really helps the class is to have an instructor who gets up in the machine and shows the operators how to actually set the machine and how to run it—and how to be able to run all the various types of machines.”