Engineers from the City and Borough of Juneau are taking a close look at damage the temporary levee sustained during the record-breaking glacial outburst flood on the Mendenhall River last week.
Some sections of the levee leaked, flooding a couple dozen homes. But it protected hundreds of others.
Nick Druyvestein, an engineering associate at the city, has spent the week inspecting each HESCO block that makes up the levee built along 2.5 miles of the river.
“I’m looking for tears in the fabric, any damage to the wire mesh, popped welds — really just looking to see if they’re they’re still standing up straight and if there is any damage,” he said.
Some parts of the levee seeped, sank into the soil or lost sand through the bottom.
A tree punched a hole through one section near Dimond Park Field House, but the water didn’t rise high enough to flood through there.
City staff are reaching out to homeowners to find out how they saw the levee perform during and immediately after the flood. Once they gather all of that information, they’ll create a damage assessment report. The report will help the city plan repairs and improvements to the levee before the next flood.
“Our basis of design last year was to try and put everything four feet above what we saw the year before, but obviously, this year we saw higher levels in some areas,” Druyvestein said.
Water surged just inches from the levee’s top in some spots.
Nate Rumsey, the city’s deputy director of engineering and public works, said he didn’t expect it to get that close since the peak flood height was less than 17 feet.
“There was water higher on the face of the barriers in certain sections than we anticipated based on the modeling that we did,” Rumsey said.
So, city engineers say they’ll account for a potentially bigger flood as they prepare for the next major flood. They don’t have a timeline yet for when repairs will begin.
In some years, Suicide Basin has released floodwaters more than once. But subsequent releases have historically been minor. Last year that happened in October.
