HUMBOLDT — Unless you’re a potter or in need of a spa day, clay is a very stubborn medium.
Engineers with BG Consultants have come to the same conclusion and as such recommended to Humboldt council members Monday night that when it comes time to redo city streets next year that they incorporate a cement additive to better stabilize the clay base.
Core samples taken earlier this fall by geotechnical engineers with Terracon Engineering discovered “extensive clays,” said Bruce Boettcher of BG Consultants. A preponderance of water not only weakens the clay, but the moisture changes its volume.
“Then it starts shifting,” he said, undermining the integrity of the base.
The answer is to mix in either a cement slurry or cement dust into the soil and let it cure.
“This will give you a more solid road base before you chip and seal,” said Boettcher.
With routine maintenance, the process could extend the service life of the roads up to 40-plus years, Boettcher said. The streets to be repaired are 2nd, 12th, Charles and Pecan, a total of an estimated 44 blocks.
Recompacting existing materials would give the city another 5-7 years, Boettcher said.
Council members also considered surfacing the streets with 3 inches of asphalt, but the cost would be prohibitive.
In the end, council members decided on incorporating cement in some form.
Last year, the city budgeted $702,980 for street repairs. A Community Development Block Grant will fund almost $500,000 for the work with city funds making up the balance.
Because city crews have done extensive ditch work, “we’ve been able to knock off about $155,000 from the expected costs,” said Cole Herder, city administrator.
The new base bid, without incorporating a cement additive, is $581,380.
“But that’s leaving CDBG money on the table,” Herder said, noting that configuration would reduce grant funding to a little more than $406,000.
Using the cement additive will bump the overall cost to more than $768,380 with the city’s responsibility a little more than $276,294.
Council members decided the extended lifetime of the road would be worth the extra expense.
