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Current Council Agenda and Past Meeting Information

 

CITY COUNCIL AGENDA ITEM NO. 23

Meeting Date: March 28, 2006

Subject/Title: Consideration of Alternatives regarding Sound Mitigation measures for the Summerset IV Community adjacent to Highway 4 Bypass

Prepared by: Engineering: B. Grewal
Community Development: H. Sword

Submitted by: Administration: D. Landeros


RECOMMENDATION
1. Consider alternatives regarding sound mitigation measures for the Summerset IV Community adjacent to Highway 4 Bypass; and
2. Provide direction to staff.

PREVIOUS ACTION
On March 14, 2006, the City Council received an informational report from Councilmember Beckstrand on the Highway 4 Bypass Segment 3 and sound mitigation for the adjacent Summerset IV Community.

BACKGROUND
The Environmental Impact Report (EIR) for the Highway 4 Bypass was approved in 1994 and set the general conditions and mitigations for various impacts, such as noise, to existing residential and non-residential developments. Any project approved around the Bypass project after 1994 was required to mitigate and provide appropriate open space buffers or noise barriers.

The Summerset IV EIR was prepared in 1995 and was approved as a part of Vesting Tentative Map 7940 in 1997. The public improvements for the project were accepted by the City in 2004. The EIR for Summerset IV determined that a setback of at least 540 feet from the centerline of the proposed Bypass would adequately mitigate all noise impacts on Summerset IV residents resulting from traffic on the proposed Bypass and comply with the noise element of the City’s General Plan as shown below:

Where it is not possible to reduce noise in outdoor activity areas to 60 dBA or less using a practical application of the best available noise reduction measures, an exterior noise level of up to 65 dBA may be allowed provided that available exterior noise level reduction measures have been implemented and the interior goal of 45 dBA is met.

All of the residences constructed in Summerset IV have met or exceeded this 540 foot offset criteria thus the mitigation requirements of the project EIR has been satisfied.

The Bypass Authority was responsible to mitigate sound for the Summerset I and II communities as they were existing projects when the Bypass EIR was approved. Summerset III, however, was approved after the Bypass was approved and the developer and Bypass Authority entered into an agreement where the developer would provide funding to the Bypass Authority which would then construct a wall at the appropriate location and elevation when the roadway was built. The soundwall in existence along Summerset I is 14 feet high and the proposed soundwalls for Summerset II and III will be 14 feet in height due to the proximity of these residences to the centerline of the Bypass. The proximity from the centerline to Summerset I, II and III residences are 373 feet, 128 feet and 130 feet respectively. The proximity from the Summerset IV residences to the centerline of the Bypass is 581 feet.
The City Council held a town hall meeting in November 2005 at the Summerset II clubhouse to discuss the state of the City. One of the requests from the participants of that meeting was to gain more information on the soundwalls along the Summerset communities and the Bypass. Staff from the Bypass Authority and the City met twice over the last two months. In response to concerns raised by the residents of Summerset IV, the Bypass Authority’s noise consultant subsequently analyzed potential noise levels at the rear of the residences in Summerset IV closest to the Bypass based on projected 2025 traffic volumes on a 4-lane Bypass (initially two lanes will be constructed), which would result in noise levels of up to 63 dBA at the rear of those residences. A range of alternatives were proposed to mitigate this sound level from rubberized asphalt to varying lengths of soundwall along the travel way. On March 9, 2006, the Bypass Authority Board considered the following three alternatives:

1. Rubberized asphalt (3 dBA sound level reduction)
2. 8 foot height soundwall extending approximately 1,500 feet south of Fairview Avenue (5 dBA sound level reduction)
3. 14 foot high soundwall extending approximately 3,000 feet south of Fairview Avenue

The Bypass Board voted to implement alternatives 1 and 2 with the condition that the City participate financially in the landscape installation along this area. The residents desire the 14 foot high wall of lengths varying from approximately 1,800 to 3,000 feet, thus they want the City to fund the difference between the 8 foot wall approved by the Bypass Board and the 14 foot high wall. The cost differences between these alternatives will be covered in detail in the fiscal impact portion of this report. The following matrix summarizes the sound reduction achieved with the various alternatives:

Mitigation Measure Sound Reduction (dBA) Sound Level at Rear of Residence (dBA)**
None (540 offset only) 0 63
Rubberized Asphalt 3 60
8’ high wall – 1,500’ in length 5 58
Rubberized AC and 8’ wall – 1,500 in length 8 55
14’ high wall - 1,500 in length not studied not studied
14’ high wall – 3,000 in length not studied not studied
**All sound levels are based upon a four lane facility at year 2025 traffic volumes

FISCAL IMPACT
The City’s development fee program does not include soundwalls as they are typically project specific noise mitigations. Any alternative selected will need to be funded from another source such as the General Fund for example.

The Bypass Authority has conditioned its decision to implement alternatives 1 and 2 above on the City’s agreement to participate financially in the installation of landscaping in the amount of $200,000. The approximate costs to the City of all the available alternatives are as follows:


Description Wall Landscaping Total
Rubberized AC and 8’ wall-1,500’ in length $0 $200,000 $200,000
8’ wall – 3,000’ in length $375,000 $200,000 $575,000
8’ wall – 1,500’ with a fortified foundation $165,000 $200,000 $365,000
14’ wall – 1,500’ in length $210,000 $200,000 $410,000
14’ wall – 3,000’ in length $705,000 $200,000 $905,000
*Cost estimates are based upon $200/LF for an 8’ wall, $300/LF for a 14’ wall and $275/LF for an 8’ wall with a fortified foundation. All wall options include $150,000 for design, implementation, construction services and Caltrans approval.

Attachments:
Proximity Map
Bypass Authority Alternatives Map

City Administration
City of Brentwood City Council
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Brentwood, CA 94513
(925) 516-5440
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E-mail allcouncil@brentwoodca.gov