I-10 Twin Peaks Traffic Interchange, Environmental Assessment

Affected Environment and Environmental Impacts October 2005
are estimated to be $32,800 ($2 per square foot, 820 feet long and 20 feet wide);
therefore, the cost per benefited receiver would be $31,138 which is less than the
$35,000 per benefited receiver recommended by ADOT. Because this wall meets
ADOT cost effectiveness criteria, this wall would be constructed.
A slight adjustment to the existing privacy wall height along Twin Peaks Road
was necessary. A segment of privacy wall along the south side of Twin Peaks
Road as it approaches the connection with the proposed Twin Peaks Road
extension is shorter than surrounding walls. Although other privacy walls in the
area are effective at mitigating traffic noise with a 6.5-foot height, a short segment
(111 feet in length) of 4.5-foot wall results in higher noise levels for RS25 and
RS26. Increasing the height of this wall from 4.5 feet to 6.5 feet to match the
surrounding walls would cost approximately $14,430 (to completely reconstruct
the wall) is effective at reducing traffic noise levels at these two receiver locations
by 5 dBA, and would result in a cost per benefited receiver of $7,215. This wall
would be constructed.
Although noise walls are the most common method of traffic noise mitigation,
other methods were considered for reducing noise exposure to residents along
Twin Peaks Road. One of the reasons traffic noise levels are relatively high along
Twin Peaks Road is the existing roadway surface. The existing surface of Twin
Peaks Road through Continental Ranch is in fair to poor condition. The pavement
shows signs of low to medium severity deterioration, rutting, and various types of
cracking. The Town of Marana proposes to resurface Twin Peaks Road west to
Silverbell Road with RAC which would improve drivability of the roadway and
decrease the noise generation from the tire-pavement interface. Although the FHWA
would not participate in the funding of roadway resurfacing with RAC, the Town of
Marana would fund this overlay.
Linda Vista Boulevard (Receivers LVR1, LVR5, LVR7 – LVR10, LVR13-16, and
LVR21)
Receiver LVR1 – The greatest increase (14 dBA) and the highest noise level (67
dBA) in this area was predicted at LVR1, which exists near the proposed
intersection of Twin Peaks Road/El Camino de Mañana/Linda Vista Boulevard.
Although noise levels at this residence were predicted to approach or exceed the
NAC for residential land uses, this residence would be displaced by the proposed
improvements; therefore, mitigation for this receiver was not considered.
Receiver LVR5 – Traffic noise levels at receiver LVR5 (66 dBA) were predicted to
exceed ADOT’s noise abatement criteria. This residence is a single isolated
residence widely separated from neighboring properties on the north side of Linda
Vista Boulevard. ADOT’s noise policy does not consider mitigation of receivers
set apart from other receivers reasonable; therefore, this wall would not be
constructed.
Receiver LVR7 – Traffic noise levels at receiver LVR7 (65 dBA) were predicted to
exceed ADOT’s noise abatement criteria. This receiver, which sits on the south
side of Linda Vista Boulevard, is a newly constructed residence with a solid
Interstate 10 Traffic Interchange at
Twin Peaks/Linda Vista
4-59
Project No.: NH-010-D (AIW)
TRACS No.: 10 PM 236 H5838 01D