Early Warning Frost Detection System

Occurrence of freeze and thaw conditions in rural roadway subgrades throughout the years resulted in significant labor efforts from Whatcom County Public Works engineers to monitor and evaluate conditions for implementing road restrictions. Extended periods of frost conditions followed by warmer temperatures can result in extensive damage to the road system if restrictions are not applied. Previously, subsurface temperatures were measured manually at various locations throughout the county to assist with evaluation of roadway conditions. Recently, a network of automated measurement and remote communication systems were designed and implemented to facilitate improved monitoring and response for the County engineers. Sixteen remote monitoring locations were selected throughout the county and at each site a 1-meter long tube with 18 thermistors at 50 mm spacing was installed into the roadway subgrade. Additional instrumentation at each site included ambient air temperature sensors and moisture sensors for the datalogger enclosures. Data is collected and transmitted to a web-based data management system for County personnel to access, and to provide alarm notifications to County personnel with indications as to when temperature thresholds are exceeded. Having the automated system allows the County to monitor the thaw process more accurately and be more confident with respect to when road restrictions are applied and their duration. The current monitoring system has increased the effectiveness and efficiency of the County’s rural roadway management process during freeze/thaw cycles, resulting in significant savings in operating and maintenance costs.