Big changes are coming to the 120 Bypass.
Ground could start turning as early as 2018 on three major interchange projects that could cost as much as $85 million.
uCalifornia’s first diverging diamond interchange at Union Road.
uThe creation of a partial cloverleaf interchange at McKinley Avenue.
uA revamp of the 120 Bypass/Highway 99 interchange.
Regional and city officials are hoping to secure federal funding for the 120 Bypass/Highway 99 interchange. It is a major project they will be stressing the regional importance of to federal officials during next month’s San Joaquin County One Voice lobbying to Washington, D.C.
The city is also seeking federal assistance with the McKinley Avenue interchange.
Manteca is in the design plan and specification phase for the Union Road diverging diamond project expected to cost around $15 million — $10 million less had a traditional interchange design been employed. It is being targeted for physical work to start as early as 2018.
The engineering firm of MT&C that Manteca has hired to design the Union Road interchange has completed a traffic operations analysis and has submitted geometric approval drawings to Caltrans. They have also had a focus meeting with Caltrans on traffic issues.
Manteca opted to pursue a diverging diamond interchange for Union Road instead of upgrading the existing structure to a partial cloverleaf. It means motorists getting on and off Union Road at the 120 Bypass will never have to worry about their turn movements being stopped by a red light when Manteca becomes the first California city to employ a diverging diamond interchange.
The diverging diamond design calls for traffic lanes crossing on either side of the bridge structure so northbound traffic would cross the bridge on the west side instead of the east side with the southbound lanes on the east side instead of the west side. Once they clear the bridge they are switched back.
The on and off ramps along with the flipping of the lanes creates two semi-diamond shaped intersections on either side of the bridge. This eliminates the need for traffic from both directions on Union Road as well as that coming from the 120 Bypass to pass through traffic signals to exit an off ramp or to get into an on ramp. The project will also include ramp meter signals such as now are in place on the Lathrop Road/Highway 99 interchange.
The project will also include Manteca’s first separate pedestrian/bicycle bridge across the 120 Bypass to address growing concerns about safety as more and more walkers head across Main Street, Union Road, and Airport Way as housing develops south of the 120 Bypass. None of the existing overpasses have sidewalks or protected bicycle lanes. The diverging diamond design as employed in other states require pedestrians to cross into the middle of the bridge and then cross back to the edge at two signalized intersection.
It would involve building a tunnel under off and on ramps on the east side of the bridge and looping a shared two-lane bicycle/pedestrian path up to the overcrossing where a wall would separate it from the traffic lanes. The Class I bicycle path would be American with Disabilities compliant. It also would have stairs that would allow walkers wanting to — and able to do so— to take a shortcut bypassing the loop to reach the bridge deck.
The city is now in the process of buying up right-of-way for the McKinley project that could cost $40 million overall. The first purchase contract is before the City Council when they meet Tuesday at 7 p.m. at 1001 W. Center St. Additional offers are being discussed as well in a closed door session on Tuesday.
Manteca’s fourth interchange on the 120 Bypass being pursued at McKinley Avenue will be the city’s first partial cloverleaf.
But in order to save money the city is considering an option that would allow the interior loop onramps to be built at a later date.
That means the initial construction would have all left turns from McKinley Avenue to 120 Bypass onramps go through signalized intersections just as they currently do at the Airport, Union, and Main interchanges. When the loops are completed northbound McKinley Avenue traffic will be able to get onto westbound 120 without going through a traffic signal as would southbound McKinley to eastbound 120.
A full cloverleaf interchange — which is not being proposed — eliminates the need for any traffic signals.
There is $7.6 million set aside to help cover the cost of interchange work. It includes what is left from a federal grant, Regional Transportation Impact Fees collected on new growth and set aside from the last Manteca Redevelopment Agency bond issuance. The overall project could cost as much as $40 million.
It will include a separated bike path that eventually will connect with the Atherton Drive bike path to provide access to Big League Dreams and the envisioned family entertainment zone.
Manteca would like to start work on the interchange by 2018 with completion by 2020.
120 Bypass/Highway 99
Unlike Union Road and McKinley Avenue that are city projects, plans to improve traffic flows and safety at the 120 Bypass interchange with Highway 99 is the concern of Caltrans.
San Joaquin County Council of Governments working with Caltrans District 10 are pushing for a target of 2019 to break ground on a permanent solution designed to reduce carnage on the 120 Bypass caused by traffic backups heading eastbound on the Bypass as it approaches Highway 99.
There are two alternates are being considered for the long-term improvement.
The first could cost as much as $40 million. It would widen the connector to southbound 99 to two lanes, construct braided ramps (that are physically separated from freeway lanes) at the Austin Road interchange and replace the Austin Road crossing to provide an additional southbound 99 through lane. In some instances braided ramps require constructing bridge structures to send traffic above other lanes.
The second would cost upwards of $29 million would widen the connector to two lanes, permanently close Austin Road on and off ramps and replace the Austin Road overcrossing to provide an additional southbound 99 through lane.
To contact Dennis Wyatt, email firstname.lastname@example.org