12 ATTACHMENT 6 - Laserfiche WebLink

MEMORANDUM date: 20 February 2014 pages: 1 name: company: email: Kevin Ebrahimi SummerHill Homes kebrahimi @shhomes.com from: Joshua M. Roper, PE, LEED AP subject: 5850 West Las Positas Boulevard—Pleasanton,California Southern Property Line Noise Barrier CSA project number: 13-0602 As requested,this memo discusses specific acoustic concerns for the planned six-foot tall noise barrier along the southern property line of the residential project at 5850 Las Positas Boulevard in Pleasanton. The barrier will separate the project site from the adjacent Arroyo Mocho Canal,as well as the existing single-family residences beyond. An environmental noise assessment was prepared for the project which is summarized in a report dated 12 December 2013. For reference,a 3-decibel change in environmental noise is generally considered a just-perceivable difference. Consider the following: • Barrier Height:You have asked whether increasing the barrier height from six to eight feet would provide a practical benefit in shielding the existing residences across the canal from on-site activity. The project includes a vehicle circulation path and parking in the southern portion of the site. Increasing the barrier height would reduce vehicle noise by approximately 1 to 2 decibels, which would not be distinguishable at the existing residences. • Barrier Reflections: You have asked if noise from the roadways and sports fields south of existing residences(across the canal)will be reflected back to those residences. The noise barrier will be precast concrete with a textured"grapestake"surface. Planted vines will be added on-site,and will grow to the canal side of the wall.These features will help reduce reflectivity of the barrier. In addition, shielding from the intervening houses(generally one to five rows)and distance attenuation from the reflected path-of-travel across the canal will help limit reflected noise. The noise barrier is estimated to increase average noise levels from vehicles on these roadways,and occupants moving around the sports fields, by 2 decibels or less,which would not be distinguishable at the existing residences. Please call with any questions. Acoustics Audiovisual Telecommunications * * Security 100 W.San Fernando Suite 430 Son Jose CA 95113 T 408 295 4944 F 408 295 4949 www.crosalter.com Charles M. Salter ASSOCIATES INC.