The City of Alameda, California, is distinguished by its island setting, but, the island setting can come with its challenges – the City is vulnerable to the impacts of climate change, including rising sea and groundwater levels, more severe droughts, intense storms and other impacts.
Ironically, while Alameda is famous for its amazing views of San Francisco, a city of steep hills, Alameda is as flat as it gets. With less than 140 miles of mainlines, the City operates 42 pump stations. Founded in 1853, Alameda still has old clay pipe in the ground, which can be a source of infiltration. Infiltration from stormwater would be difficult enough to manage but Alameda’s shallow groundwater layer adds another layer of challenge. Large portions of this shallow groundwater layer are hydraulically connected to the Bay. As the sea rises, so will this groundwater layer. Rising groundwater is yet another factor to consider when prioritizing pipes for replacement.
Alameda operates its sewer collection system under a federal consent decree, along with seven other East Bay agencies. The main objectives of the decree are to reduce infiltration and inflow (I/I) and sanitary sewer overflows. The consent decree contains a number of work requirements to achieve those objections, including the annual rehabilitation of 2.6 miles of sewer main with associated manholes and lower laterals, pump station renovation, implementation of a private sewer lateral program, a rigorous cleaning and inspection program and root control, among other requirements.
Alameda’s Public Works Department has been working with Duke’s since 2014 to remove roots from its mainlines – a total of 110,578 ft of pipe in its Root Foaming program with pipe sizes ranging from 6 to 21 in., of which 86 percent are in the 6- to 8-in. in range.
Duke’s applies Razorooter II, a herbicide-laden, thick foam with the consistency of heavy shaving cream. The Duke’s crew inserts a hose from manhole to manhole. The entire system is treated as the foam compresses against pipe surfaces and penetrates cracks, joints and connecting sewers. Roots are killed on contact inside and outside the pipe walls, decay naturally and slough away, with regrowth delayed for two to three years, without harming trees or other above ground vegetation.
Online Analytic System
In 2020, Alameda incorporated Duke’s online analytic system. Using its own crew and equipment, Duke’s creates a digital map of assets (pipes and manholes) for ease of locating and providing real-time progress views of pipes assigned for root foaming treatment, in progress, completed or requiring attention by the city. In turn, this helps Alameda store, update and retrieve accurate data instantaneously, meet compliance challenges, better collaborate with system operators/construction contactors and thus reduce time dramatically, and it integrates into their current asset management platform. The system also captures and updates attribute information during field work and record in database, including pictures and videos.
“The ability to receive real-time information, without having to send personnel to the field to verify and track work being done day-to-day is invaluable,” said Alameda director of public works Erin Smith. “It also drastically reduces planning time, we don’t have to create map books, we simply send a spreadsheet, listing which pipes to treat each year, and Duke’s takes care of the rest. And, year to year we have the history of the pipes at our finger tips.”
Alameda rotates treatment of mainlines, 50 percent one year, the remaining the second year. However, because Alameda has an aggressive replacement program, many pipes drop out of the program once they are replaced.
In Alameda, although property owners own their lower laterals, Alameda takes over responsibility through its lower lateral maintenance program. And, most of the reportable overflows come from lower laterals.
“Currently, our maintenance program for lower laterals is primarily driven by service calls. However, we are working toward developing a preventive maintenance program that includes cleaning, root control and condition assessment,” Smith said. “The idea is to identify the problem before the service call occurs. We are working to inspect the lower laterals a sub basin at a time and have the information stored in our maintenance management system. This data will allows us to develop an optimized maintenance program where limited resources are focused on laterals that need it. We look very forward to working with Duke’s to leverage their GIS system for lower laterals as well as mainlines.”
Another reason Alameda is looking to collect this condition data is to possibly update its 20-year rehabilitation plan. In 2015, the City developed a master plan for the entire sewer system. In addition to assessing capacity, a risk model was built that assigned a risk score to each sewer main based on Likelihood of Failure (LOF) (condition) and Consequence of Failure (COF) (the impact of failure). The risk scores are what informs the 2.6 miles of mainline to be rehabilitated each year. Lateral condition was not used; however, the City is considering it as another factor for prioritizing main line rehabilitation.
Alameda also intends to refine its GIS data for manhole rim levels, depth and condition.
“Duke’s digital analytics platform is integral to refining our risk model. As the sea continues to rise, we will need to be crystal clear on prioritizing replacement of not only mains, but also laterals and manholes,” Smith said. “Having the data digitally is great, but, more importantly is the ability of the system to slice, dice and analyze giving us the information we need , in almost real time fashion, to make the right decisions to preserve our city.”