For two months, the contractor on the SR 99 Tunnel Project, Seattle Tunnel Partners (STP), has been working to determine what caused the stoppage of the SR 99 tunnelling machine on 06.12.2013. WSDOT and STP have identified two contributing factors: a clogged cutterhead, and high-temperature readings indicating there were other factors to explore. Click here and us/69 for tunnelbuilder archive. Further information from http://www.wsdot.wa.gov/Projects/Viaduct. 07/14.