June 25 2019

Mark Thomas Designs California’s First Diverging Diamond Interchange

The City of Manteca recently broke ground on construction of California’s first Diverging Diamond Interchange, at SR 120 and Union Road. The Diverging Diamond Interchange, commonly abbreviated DDI, is a cutting-edge design that reduces conflict points between vehicles and moves traffic more efficiently through the interchange. DDIs have been gaining popularity throughout the United States since the early 2000s, but until now, one had not been constructed in California. The DDI is unique in that traffic on the freeway overpass is shifted to the left side of the road, before being shifted back to the right. The graphic below illustrates this movement.

Construction of the DDI at SR 120 and Union Road will modify the existing interchange to add additional traffic capacity and improve operations. As the prime consultant in charge of design of the modification, Mark Thomas worked closely with the City of Manteca and Caltrans to gain project approval for the DDI. Caltrans guidelines and approval processes were being developed as design work on SR 120/Union Road Interchange progressed, so we partnered with Caltrans District 10 and Headquarters to gain acceptance for the design.

Mark Houghton, City of Manteca Public Works Director, noted “In fact, Mark Thomas staff worked collaboratively during the early design stages of this project with both state and federal engineers to not only design this project, but also drafting what are now adopted standards that will guide the development of future similar interchanges”.

We also developed the concept for a grade-separated Class I bike path through the new interchange. Union Road is a key crossing of SR 120 in the City’s bicycle master plan, and there is not currently any sidewalk or bike path through the area. The new Class I path will provide a 12-foot wide grade-separated trail that eliminates all bicycle/vehicle conflict points within the interchange to provide safe and efficient passage for bicycles and pedestrians. Mark Thomas designed a similar path through the US 50/Watt Avenue Interchange, shown in use below.

Learn More

The SR 120/Union Road Interchange project is currently under construction and is scheduled to be completed in 2021. For more information on the project, please visit

March 26 2019

Julie Passalaqua Leads Interactive Mentorship Activity

Julie Passalacqua, Mark Thomas’ Structures Division Manager, recently led a group of 10 young women  from the Sacramento chapter of Women’s Transportation Seminar (WTS) on a train trip to Rosie the Riveter National Park in Richmond. The trip was part of WTS’ Transportation YOU, an outreach and mentorship program for girls ages 13 to 18 that introduces them to a wide variety of transportation careers, and cultivates their interest and efficacy in science, technology, engineering, and math (STEM). Julie has been a integral part of the Sacramento Chapter’s Transportation YOU initiative, currently serving as co-chair of the program. Mark Thomas is proud to support Julie’s work with WTS, exposing more young women to careers and mentors in STEM.

Read more about the outing here:

A Day with Rosie: Uplifting Women in Transportation

October 1 2018

Matt Stringer Promoted to Survey Division Manager

We’re excited to announce that Matt Stringer, PLS, CFedS has been promoted to Survey Division Manager. Matt has been with Mark Thomas since 2005. In that time, he has managed all phases of survey services in support of bridge, transportation, utility, and water/wastewater infrastructure design. He has also led our Sacramento and Bay Area surveying teams.

In his new role as the company’s Survey Division Manager, Matt will continue to deliver major survey contracts statewide and will be responsible for managing and mentoring our growing team of survey managers, office staff, and field crews throughout the state. Matt is taking over leadership responsibilities from Larry Johnson, who has been working with Matt to transition his corporate responsibilities. Larry will continue to manage high-profile surveying projects for Mark Thomas.

Congratulations Matt!

August 2 2018

Mark Thomas Ranked One of California's Top Design Firms

We’re excited to be ranked #38 by Engineering News-Record (ENR) on their 2018 list of the top California design firms! Our #15 ranking in Transportation represents our long history of delivering roadway, highway, bridge, and active transportation improvements throughout the state. Our rank of #9 in Surveying and Mapping is thanks to our survey division’s performance providing critical information for transportation, transit, utility, and water/wastewater infrastructure projects.

Learn more about the top firms here:

May 29 2018

Zach Siviglia Promoted to Principal

We’re excited to announce the promotion of Zach Siviglia to Principal. Zach has been with Mark Thomas for seven years. In that time, he has led the development of freeway improvements, bridges, highway interchanges, local roadway improvements, bicycle facilities, civil related transit improvements, streetscape designs, and downtown infrastructure improvements. Zach is currently leading the development of designs for the I Street Bridge replacement and the new Broadway Bridge, both of which will improve connectivity between Sacramento and West Sacramento.

As Principal, Zach will continue to manage major transportation projects in the Sacramento & Central Valley and will lead development of our emerging services. Join us in congratulating Zach!

April 16 2018

Welcome Darin Johnson!

Mark Thomas is proud to welcome Darin Johnson, PE. Darin recently joined our Southern California team as a Senior Associate and Transportation Division Manager.

Darin brings more than 30 years of experience delivering improvements to local roadways and Caltrans facilities. Working with President Rob Himes, Darin will leverage his strengths managing multidisciplinary projects to help us better serve our Southern California clients. He will also help manage and mentor our growing team of Southern California transportation engineers and technicians.

Darin can be reached at or 949-477-9000. Please join us in welcoming Darin to Mark Thomas!

November 14 2017

Christine Anderson to Serve As CLARB President

Mark Thomas’ Christine Anderson has been elected the President of the Council of Landscape Architectural Registration Boards (CLARB) 2017–2018 Board of Directors, which she will serve through September 30, 2018. As President, Christine will serve as an ambassador and liaison to industry organizations and allied professions. Within CLARB, she will focus on leadership development, diversity and foresight.

Christine is an integral member of our Landscape Architecture and Urban Design division, preparing planning and construction documents for streetscapes, bridges, active transportation, downtown revitalizations, and park and recreation projects.

She previously served CLARB in the roles of President-Elect (2016-2017), Vice President (2015-2016), Treasurer (2013–2015), Region 5 Director (2011–2013), a member of CLARB’s Board Self-Assessment Workgroup (2012–Present) and a member of the Task Analysis Focus Group (2010–2011).


Since 1970, CLARB has been dedicated to ensuring that all individuals who affect the natural and built environment through the practice of landscape architecture are sufficiently qualified to do so. CLARB works to protect the public’s health, safety and welfare by establishing and promoting professional licensure standards for education, experience and examination required for the profession of landscape architecture. CLARB’s members include the licensure boards that regulate the profession of landscape architecture in the United States; District of Columbia; Puerto Rico; and the Canadian provinces of Alberta, British Columbia and Ontario.

September 21 2017

Transforming Downtown Sacramento for Park(ing) Day

Last weekend we participated in the American Society of Landscape Architects’ California Sierra Chapter annual Park(ing) Day event in Downtown Sacramento. Park(ing) Day temporarily transforms on-street parking spaces into creative mini-parks designed to illustrate alternative uses of public space and celebrate what makes Sacramento special. Located right at the front steps of the state capitol, the theme for this year’s event was “Creative Capitol”.

To create a fun and engaging environment for attendees and highlight the changing face of Downtown Sacramento, the Mark Thomas parklet’s centerpiece was a Caplinko game – a take on the classic Plinko game from The Price is Right, but with a special Sacramento twist. To support the game, volunteers constructed a living room area from colorfully painted repurposed wood pallets, placed potted plants and synthetic turf, and conducted an informal opinion survey of the potential redevelopment of the Capitol Mall corridor. The Caplinko board itself featured the Capitol Mall corridor and landmarks in the surrounding area, with players aiming for various prizes at the bottom.

The event was a huge success – we had a blast coming up with the game and chatting with everyone that stopped by to play. It was also a great opportunity to show community members the benefit and ease of adding public gathering spaces in even the most urban environments. We are already planning for next year!

Check out our Caplinko game in action here:

Special thanks to our sponsors Village Nurseries, ARC Document Solutions, Riot Creative Imaging, and Purchase Green Artificial Grass.

June 12 2017

Julie Passalacqua to Lead Mark Thomas’ Structures Group

Mark Thomas is proud to announce that Julie Passalacqua, PE has been promoted to leader of our statewide Structures Division. Our Structures Division engineers partner with clients to deliver transportation, flood control, and wastewater structures projects throughout California. This includes the design of new bridges, bridge replacements and rehabilitations, retaining walls, soundwalls, flood walls, water reservoirs, pump station housings, and other structures.

Julie has been with Mark Thomas since 2006, and in that time has established herself as a trusted client partner, excellent mentor, and accomplished structures designer. She has managed dozens of structures projects statewide, including Highway Bridge Program (HBP) bridge rehabilitations and replacements; freeway overcrossings, undercrossings, and interchange structures; railroad grade separations; and pedestrian trail bridges and overcrossings.

Julie is actively involved in the WTS Sacramento Chapter and co-chairs TransportationYOU, where she mentors young women ages 13-18 and provides an introduction to a career in transportation engineering.

May 24 2017

Our Innovations Move California Forward

Mark Thomas recently participated in Caltrans District 8’s innovation fair in San Bernardino. The fair was an opportunity for Caltrans, consultants, and other agencies to come together and show how their innovative designs have improved California’s transportation infrastructure. As an exhibitor, we highlighted how our innovative solutions are creating benefits at the following interchanges:


March 1 2017

Mark Thomas Employees Celebrate Rebranding

We recently revealed our rebranding with a companywide party at Make Westing in downtown Oakland. Not only did it allow our Mark Thomas team members to preview our new look ahead of the pu blic release, but it was a great opportunity to connect and network with colleagues from across the state, both old and new.

February 20 2017

Bay Area Employees Give Back

Mark Thomas team members recently participated in a volunteer event at Second Harvest Food Bank. On a quarterly basis, our team members help the food bank by sorting donations at Second Harvest Cypress Center in San Jose. Second Harvest distributes more than one million pounds of nutritious food each week to low-income people in in San Mateo and Santa Clara counties.

February 20 2017

Keeping Up to Date at the CTF Forum

Mark Thomas team members recently attended the California Transportation Foundation (CTF) Forum. The Forum, which we attend annually, provides an opportunity to connect with our clients and teaming partners, and hear the latest updates on California transportation legislation from lawmakers and administrators.

We are proud to be a legacy sponsor of CTF, helping them meet their goals of providing assistance and mentorship to the transportation industry’s current and future leaders, and supporting those in need within the transportation industry.