Ze­bra mus­sels on wa­ter in­takes

Plans un­der­way to treat wa­ters, avoid dam­age of an in­fes­ta­tion.

Austin American-Statesman Sunday - - METRO & STATE - By Mark Wil­son

Clus­ters of in­va­sive ze­bra mus­sels have been found cling­ing to fil­ter­ing screens in Austin’s wa­ter util­ity in­take pipes on Lake Travis.

Divers made the dis­cov­ery Sept. 7 while in­spect­ing the screens at the Hand­cox Wa­ter Treat­ment Plant on Lake Travis. The plant uses three in­takes set one above the other at dif­fer­ent depths to bring in wa­ter.

At the be­gin­ning of the month, divers went down to make a rou­tine in­take switch. The in­takes are opened or closed de­pend­ing on lake wa­ter lev­els.

In the first in­take, the divers saw that al­most half of one screen was cov­ered with mus­sels. Then, more than 20 per­cent of a sec­ond screen was cov­ered, said Mehrdad Morabbi, Austin Wa­ter’s treat­ment oper­a­tions man­ager.

The screens are oc­tag­o­nal and mea­sure roughly 24 feet by 30 feet, he said.

Divers used a pres­sure washer to clear out the lower in­take screen and be­gan work on the top in­take, which Morabbi said usu­ally does the brunt of the work at the fa­cil­ity. How­ever, time con­straints only al­lowed them to re­move roughly 50 per­cent of the mus­sels on that in­take.

Divers will have to come back in the win­ter to fin­ish the job.

Morabbi said Austin Wa­ter com­pletely shuts down its in­takes while divers are work­ing, so they have to wait un­til wa­ter de­mand is lower.

The dis­cov­ery comes more than a year af­ter the crit­ters ap­peared in Lake Travis, and about seven months af­ter Texas Parks and Wildlife Depart­ment of­fi­cials first spot­ted the lar­vae of the ra­zor­sharp mus­sels in Lady Bird Lake.

Ear­lier this year, 14 bod­ies of wa­ter and five river basins in Texas — in­clud­ing Lake Austin and Lake Ge­orge­town — were found to be in­fested with ze­bra mus­sels.

Seven more ei­ther tested pos­i­tive or were sus­pected of con­tain­ing ze­bra mus­sels.

In other parts of the coun­try, in­fes­ta­tions have led to mil­lions — in some cases, bil­lions — of dol­lars in dam­age to in­fra­struc­ture.

A 2009 re­port from the Aquatic

Nui­sance Species Task Force found that ze­bra mus­sels cost the power in­dus­try $3.1 bil­lion through much of the 1990s by clog­ging pipes in the Great Lakes.

“It’s con­cern­ing, but it’s not un­ex­pected. We knew that typ­i­cally the first sea­son is the worst sea­son,” Morabbi said. “This is his­tor­i­cally (the case) based on what we’ve stud­ied and (who) we’ve talked to.”

Austin Wa­ter has hired a con­sult­ing firm that is about to wrap up a pre­lim­i­nary engi­neer­ing study to ad­dress the prob­lem in the fu­ture.

Author­i­ties are con­sid­er­ing chem­i­cal op­tions to treat the wa­ter for mus­sels, but any change in treat­ment has to be ap­proved by the state.

The Hand­cox fa­cil­ity is one of three Austin Wa­ter treat­ment fa­cil­i­ties. The mus­sels likely have started to swarm in­take pipes at the two other fa­cil­i­ties on Lake Austin as well.

“We in­spected the Lake Austin ones around the be­gin­ning of sum­mer,” Morabbi said, adding that those fa­cil­i­ties also will be in­spected again in the win­ter. “We ex­pect to find mus­sels in those fa­cil­i­ties too.”

Ze­bra mus­sels have con- tin­ued their steady spread across Texas since first ar­riv­ing in the state on Lake Tex­oma in 2009.

Author­i­ties said the Leg­is­la­ture pro­vided more than $6 mil­lion to Texas Parks and Wildlife from statewide man­age­ment of in­va­sive species in the 2016-17 and 201819 bi­en­nial bud­gets.

“These in­vest­ments ex­pand TPWD’s abil­ity to com­bat the spread of ze­bra mus­sels, and helps to fund a pub­lic aware­ness cam­paign, out­reach and preven­tion ef­forts, and re­search into new so­lu­tions,” of­fi­cials said.

Ze­bra mus­sels are small, only cen­time­ters in size when fully grown.

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