Construction is still at least four years away, but Sound Transit is getting a jump on gathering field information for the expansion of light rail service along I-5 from Northgate Mall to Lynnwood.
Over the next few months, Sound Transit representatives will be contacting property owners, including those along I-5 in Mountlake Terrace, for approval to access their property in order to conduct noise monitoring, vibration testing/monitoring, geotechnical drilling and survey work. This information is needed to study, evaluate and document the potential impacts of the planned Link light rail expansion, complete the environmental review process and publish the Final Environmental Impact Statement early next year, Sound Transit officials said.
After receiving approval from property owners in the form of Right of Entry authorizations, work on private and public properties will take place over the next six months or more along the I-5 corridor.
Measuring noise at homes will help Sound Transit staff determine the potential impacts of future train operations, officials explained. Noise monitoring equipment will be placed outdoors on private property to collect data on existing conditions for two to three days at each site. Officials stressed that only surrounding noise is recorded as decibel levels, actual sounds or nearby conversations are not recorded.
To evaluate the potential for vibration from future train operations on nearby buildings and homes, vibration testing and monitoring will be completed. Monitoring equipment will be placed in and around homes to record vibration data while staff and equipment are nearby during testing. Power generators may be heard and impact equipment may cause noticeable vibration during testing, but officials note that testing will be completed during normal working hours and each site should be completed in four to five hours.
In order to study soil conditions, drilling or “borings” are necessary to collect soil samples for analysis. A drill rig and truck will perform borings and remove soil samples from each site. Each bored hole will be refilled and patched to match previous conditions as closely as possible. In accordance with all local regulations borings will be done carefully to avoid soil erosion and dirt or mud from leaking into surface waters, wetlands and drainage systems. Each site may take about three days to complete.
Civil surveyors will gather topographical information and may leave paint markings or survey nails on the ground and ribbons in trees. Biologists will perform wetlands survey work and analyze plants species, hydrologic conditions and soils. Small holes may be dug but will be refilled. Survey flags may also be placed to indicate wetland boundaries and should not be moved.
Sound Transit officials are asking local residents for their cooperation while the field work takes place during the first half of 2014. The transit agency plans on releasing its Final Environmental Impact Statement on the 8.5-mile, $1.6 billion light rail expansion late this year or in early 2015.