Tasked with maintaining the city’s infrastructure, officials at Public Works have been hard at work evaluating and repairing the city’s roadways. However, not all street repair and rehabilitation projects are created equally.
Designed to withstand years of constant force, streets are composed of multiple layers, which include two layers of asphalt at the top, a base in the middle (which is composed of sand and crushed rock), followed by a subgrade (which is mainly compacted dirt) at the bottom. Depending on the condition of the roadway, engineers may elect to perform different types of rehabilitation, ranging from preventative maintenance to minor rehabilitation, all the way to major rehabilitation which sometimes entails reconstruction of the entire roadway section.
Construction crews are tearing out two layers of asphalt and one layer of base as Mission Road prepares for reconstruction.
Whenever possible, preventative maintenance is the preferred choice due to its low cost and long term benefits. “We do work on pavement that’s in good condition to keep it in good condition,” notes Algis J. Marciuska, Principal Civil Engineer for the city. “If we elect to perform preventative maintenance on a good street that exhibits minor cracking, we’re able to maintain the surface with relatively little construction.” When Public Works elects to use preventative maintenance on a street, they’re typically employing crack seals and slurry seals to maintain the street’s seal which keeps water from seeping into the pavement.
Streets that undergo minor rehabilitation require more work, with construction crews typically grinding up the roadway’s asphalt with the goal of reconstructing a new layer on the surface.
Streets that require major rehabilitation – such as Mission Road from Anderson Way to Del Mar Avenue – will oftentimes require complete reconstruction. This occurs when the road experiences subgrade failure, where both layers of asphalt and the subgrade below have failed. As one would imagine, major rehabilitation requires the most funds. Because of partial funding from the Alameda Corridor Construction Authority (ACE) for the San Gabriel Trench Project, the city was able to reconstruct a portion of Mission Road from the ground up. “These roads were used as haul routes for the ACE project,” Marciuska notes. “The roadways needed work prior to ACE coming in, and given ACE’s traffic demands, the project caused the roads to deteriorate even further. We ultimately had an agreement with them that allowed us to share the cost of reconstruction.”
After preparing a new subgrade, construction crews are now laying down the initial layer of asphalt known as the base.
Another layer of asphalt will be placed on top of the base before crews begin striping the road.
When complete funding is not available, officials must prioritize between cost, road condition, and input from the community when it comes to rehabilitating certain roadways and not others. “In 2015, we presented a pavement management plan to the City Council which classifies our streets on a scale of 0 to 100 – 100 being the finest new street, and 0 being a completely failed street,” Marciuska said. “Our average PCI score – which is the Pavement Condition Index – is currently at 52 for all city streets.”
By this time, construction crews have completed placing the final layer of asphalt. The concrete pad on the left is designed for a bus stop.
Because asphalt is a flexible material, this bus pad will allow buses to load without impacting the rest of the street.
The ultimate goal for Public Works is to work toward raising the PCI as much as possible. With the surge of projects from 2015 to 2018, they aim to raise the PCI to 56. In the short term, Public Works attempts to implement projects and maintenance using all available funding to ensure that the city’s PCI doesn’t drop. “The worst streets are the most expensive to reconstruct, and we don’t want to neglect preventative maintenance because we can stretch our dollar and the life of the street with minimal cost,” Marciuska notes. To maintain its current PCI score of 52, the city would need to spend from $3.5 to $4 million per year on its roads. As it stands, the city is currently investing $1.76 million into the Great Streets Program, with a projected investment of $1.57 million for the upcoming fiscal year. Previously, the city had only been investing $560,000 for the 2015-16 fiscal year.
A look at the newly completed Mission Road, with new subgrade, two layers of asphalt, and striping.
As for the ACE project, this was a unique opportunity for the city to improve several of its roads. “It is the largest project our city has ever seen since the construction of Interstate 10 through this area. So the ACE project is very significant, and it was a one-time opportunity to partner with ACE to get quite a bit of paving done,” Marciuska said. “Our challenge is to keep the number from dropping given our current funding, which is difficult given the required $3.5 million to $4 million in funds that it would require.”
Daren Grilley, Public Works Director/City Engineer, is optimistic about his department’s plan to address San Gabriel’s network of roads. “We have more paving projects underway than at any time in recent history, and the City Council has approved a stable source of revenue for the Great Streets program that allows us to begin a multi-year paving plan,” Grilley said. “New revenue from the State Road Repair and Accountability Act and voter-approved Measure M will also provide the boost we need to start addressing the backlog of repairs.”
This article originally appeared in the summer 2017 issue of the Grapevine.