A noise study was conducted in 2005, which predicted peak hour noise levels for the Yelm Loop. These were compared to WSDOT’s noise abatement criteria (NAC) to determine if there would be future noise effects associated with the Build Alternative. The analysis identified 24 residential properties that would exceed NAC following construction of the Build Alternative. All 24 affected properties would exceed the 10 dBA increase criteria; four of the properties would also exceed the 66 dBA criteria. Most of the affected properties are between Crystal Springs Street and Rhoton Road and are located both north and south of the proposed corridor. Two properties would be affected along Canal Road between Flume Road and 103rd Avenue. Under the No Build condition, no changes in noise would occur other than those associated with development within the surrounding area. Locations of noise receivers, and those that exceeded the NAC are shown below.
How does WSDOT decide if a noise wall gets built?
At locations where noise effects are forecasted to occur, WSDOT determines if a noise wall is feasible by evaluating whether it is physically constructible and will achieve a meaningful reduction in noise levels for affected receivers. If construction is feasible, WSDOT then assesses if it is reasonable by considering factors such as cost-effectiveness and the expected level of noise reduction for nearby homes, businesses, or other features (such as parks or hospitals).
In addition to these criteria, WSDOT Noise Policy also establishes a date of official public notification or public knowledge about a future roadway improvement project. This date establishes eligibility for consideration of a noise wall – receivers existing prior to the date of public knowledge are eligible, and receivers constructed after the date of public knowledge are not. For this project, the official date of public knowledge is when the first environmental decision (Finding of No Significant Impact) for the Yelm Loop project was published – February 1, 2000. The View Royale neighborhood was in place prior to this date and is therefore eligible for a noise wall. The Canal Estates neighborhood was developed after the date of public knowledge and therefore is not eligible for construction of a noise wall. Census data for these two neighborhoods were analyzed using the same methodology as previously described to determine if a disparate Environmental Justice (EJ) impact would occur for the Canal Estates neighborhood. This analysis concluded that there would be no disparate impact on EJ communities in the vicinity of the noise wall. EJ communities in the study area include minority populations, low-income households, and populations with limited English proficiency (LEP).
Proposed new noise walls
Future noise levels at twenty of the affected residences in the View Royale neighborhood between Crystal Springs Street and Rhoton Road can be mitigated through the construction of a noise wall. Several properties located on the north side of the corridor in the Canal Estates neighborhood would see noise levels increase from an existing 51 decibels (dBA) to 63 dBA. As described above, these properties were constructed after the date of public knowledge and therefore are not eligible for noise mitigation. The modeled noise level of 51 to 63 dBA at Canal Estates is below the NAC of 66 dBA. The proposed wall location is shown in the figure below.
For more information
To read more about the study approach, existing conditions, and effects on noise, please see Section 3.4 Noise (PDF 1.9MB).