Parts of San Rafael, a city just north of San Francisco, are sinking about half an inch per year. That might not sound like much, but altogether, it has meant that some neighborhoods — like the Canal District that borders the bay — have sunk three feet, placing them at greater risk of flooding from sea-level rise.
San Rafael isn’t alone. Cities around the world are threatened by rising sea levels, with 300 million people at risk of routine flooding by 2050. The cost of building seawalls to hold the waters back could top $400 billion in the U.S. alone.
A new startup is proposing an alternative: raise the city instead.
Terranova is building robots that will inject a slurry of wood waste into the ground, slowly lifting the land to eliminate historical subsidence and, hopefully, prevent those parts of the city from flooding.
“The canal district is really far under sea level,” Laurence Allen, co-founder and CEO of Terranova, told TechCrunch. The city has been working with flood consultants to find a solution, he said.
“The answer, every answer every time, has been like $500 million to $900 million of seawalls, which if you’re from San Rafael, you know they’re not even close to being able to afford that. There’s about 60,000 people and a significant portion — surprisingly for a city in Marin — are living in poverty.”
Terranova says it can protect San Rafael and other cities like it for a fraction of the cost. In San Rafael’s case, the startup has quoted $92 million to lift 240 acres four feet.
The company recently raised $7 million in a seed round led by Congruent Ventures and Outlander with participation from GoAhead Ventures, Gothams, and Ponderosa, TechCrunch has exclusively learned. The oversubscribed round values the company at $25.1 million.
Lifting land by injecting stuff underground isn’t new. Terranova’s pitch is that it has developed some novel approaches that make it cheaper.
First is the material: Waste wood is inexpensive and easy to obtain. The startup mixes it with other materials that it wouldn’t disclose to turn it into a slurry. The result is pumped from a 20-foot shipping container to the second cost-saving item: a robotic injection device. The tracked robotic units autonomously rove around the work site, drilling wells through which the wood slurry is delivered to depths of around 40 to 60 feet.
So long as the slurry remains wet underground, the wood shouldn’t decay and the company can sell carbon credits to offset costs, Allen said.
All of this is managed by software that Terranova has developed. The company uses public geographic information coupled with data from cores drilled throughout the state of California, mostly taken during the construction of water wells. With that, it has created a model of the subsurface that informs injection patterns, which are determined by a genetic algorithm.
On the back end, city planners, contractors, and other stakeholders can use a SimCity-like tool to sculpt the virtual landscape.
When plans are finalized, they guide the robotic injectors, telling them both where to inject and how much. Human operators remain on site as a safety precaution, Allen said. Once the robots are done injecting, it takes about two hours for the slurry to consolidate, he added.
Terranova has been testing both the robots and software at a pilot site for over a year, he said.
Though some experts have questioned whether the consolidated wood slurry will exacerbate earthquake shocks, Allen said the most frequently mentioned alternatives have risks, too. “We think it’ll help [with earthquakes] versus dikes and seawalls.”
The company plans to make money by splitting revenue for projects with contractors. It’s hoping the costs are low enough that the process will be attractive for a range of land-lifting projects beyond cities, including remediating wetlands that are disappearing either due to subsidence or sea-level rise.
But given the urgency of rising waters, cities are Terranova’s first priority. “I’m from San Rafael, born and raised,” Allen said. “I really want to save the city.”