On March 2, 2009, the City of Seattle adopted amendments to the Seattle Municipal Code, Chapter 25.08 on Noise Control. The amendments went into effect on June 15, 2009. They include 

• Allows the Administrator to grant noise variances for “major public project construction."
• Allows the DPD Director to grant noise variance extensions for previously granted variances (with public notice) except for temporary variances.
• Sets a 7 p.m. limit rather than a 10 p.m. limit for noisy site development activities in Lowrise, Midrise, Highrise and Neighborhood Commercial zones when residences are within 100 feet of the property. In other zones and where residences are not nearby, noisy site development activities may occur until 10 p.m.
• Updates the code to acknowledge current sound measuring methods and devices.
• Updates and strengthens enforcement procedures to provide for stop work orders, revocation of variances, citations, civil penalties and the possibility of duration limits and the modification of variance terms at the Administrator’s discretion.

The noise variance for “major public project construction” requires submittal of a noise management and mitigation plan (NMMP) that must address the noise levels and limits along the extent of the major public project, and include a range of noise protective strategies to provide for effective mitigation of noise impacts during construction.

DPD's Director's Rule 3-2009, provides more details about expected contents of a NMMP and related review processes. This includes a one-year review for major projects. Also, the DR discusses public notices and other procedural matters.