City dams are old, beat up and a vi­tal line of de­fense

$72 mil­lion in re­pairs, now un­der­way, won’t solve long-term is­sues

Houston Chronicle - - FRONT PAGE - By Lauren Caruba

Richard Long drove along empty roads that were al­most im­pos­si­ble to see, thanks to an un­re­lent­ing down­pour and early morn­ing dark­ness. He tried to fol­low the yel­low line on FM 1093 but found him­self drift­ing into turn lanes.

Long was the first to ar­rive at the Army Corps of En­gi­neers’ small of­fice off High­way 6 in west Hous­ton, where he had worked for 35 years. As he waited for his team on April 18, still be­fore 5 a.m., he wor­ried about what the wa­ter would do to Ad­dicks and Barker dams, each seven decades old and rated seven years ago by the Corps among the na­tion’s six most un­safe dams. Ma­jor re­pairs are on­go­ing.

At day­break, Long went out to check on them, as pound­ing rain drowned out all other sound. Wa­ter rushed into the reser­voirs faster than he had ever seen, trans­form­ing acres of woods and parks into lakes.

Later that day, the Corps’ dis­trict com­man­der came in from Galve­ston, fol­lowed by a dozen vol­un­teers. They would work 12-hour shifts, walk­ing along the dams and rid­ing in UTVs, search­ing for move­ment and wet spots, check­ing ground­wa­ter lev­els.

The rain fi­nally re­lented, but the wa­ter in the reser­voirs kept ris­ing. Ev­ery day. For seven days.

On April 23, the wa­ter reached 102.65 feet above sea level at Ad­dicks, a record. Two days later, at Barker, the wa­ter level hit 95.24 feet, an­other record. To­gether, at their peak pools, the reser­voirs stored 6.8 bil­lion gal­lons, enough to fill NRG Sta­dium 101 times over. The last time the reser­voirs col­lected close to that much wa­ter, it was af­ter months of re­peated storms. This time, it took only one big one.

The wa­ter would not com­pletely drain for more than two months. Hold­ing that much wa­ter, for that long, is not what Hous­ton’s dams were de­signed to do. Ad­dicks and Barker were built to pro­tect the

heart of the city by con­trol­ling the flow of wa­ter along Buf­falo Bayou. Things haven’t gone as planned.

Re­pairs to­tal­ing $72 mil­lion are un­der­way, and the Corps says there is no im­mi­nent risk of failure, but it re­al­izes the need for a longer-term so­lu­tion.

What’s at stake is the safety of the na­tion’s fourth-largest city. If the dams failed, half of Hous­ton would be un­der­wa­ter. Un­der the worst sce­nario at Ad­dicks, prop­erty dam­ages could reach $22.7 bil­lion and 6,928 peo­ple could die.

“Failure is not an op­tion for us,” Long said.

Ad­dicks and Barker were six decades old, with a long his­tory of seep­age and ero­sion, when the Corps eval­u­ated their con­di­tion in 2007. Once po­si­tioned far from down­town, they were now sur­rounded by houses and high­ways. Some res­i­dences sat within the reser­voirs, which strad­dle the En­ergy Cor­ri­dor along In­ter­state 10 and west of Belt­way 8.

De­vel­op­ment up­stream was send­ing more runoff into the reser­voirs, which were filling faster and stor­ing wa­ter for longer. Nine out of the top 10 pools for both reser­voirs have oc­curred since 1990.

“Ev­ery piece of con­crete that’s poured up­stream is go­ing to have an im­pact on these reser­voirs. Ev­ery square inch,” Long said.

The eval­u­a­tion found many as­pects of the dams — the em­bank­ments, the con­duits, the wa­ter con­trol struc­tures — were “prob­a­bly in­ad­e­quate” for an ex­treme storm, in­spec­tion re­ports show.

Ground-pen­e­trat­ing radar scans soon re­vealed a more pre­car­i­ous sit­u­a­tion. Voids had formed be­neath the con­duits on both dams. Large cracks ex­tended through the con­duits and spill­ways, which showed signs of move­ment. In 2009, Ad­dicks and Barker ad­vanced to the Corps’ worst safety classification, rat­ing a 1.

Only four other dams — out of hun­dreds across the coun­try — re­ceived that rat­ing. None was near a city as big as Hous­ton.

By 2012, the Corps had filled the voids with polyurethane and ce­ment grout, a tem­po­rary fix. Fil­ters were in­stalled to con­trol seep­age. In­spec­tions were height­ened.

The agency also cal­cu­lated ma­jor ways, six at each, that the dams could col­lapse.

The dead­li­est sce­nario for Ad­dicks in­volves the out­lets fail­ing as the pool rises to 106 feet, pro­duc­ing the stag­ger­ing loss of bil­lions in prop­erty and thou­sands of lives af­ter wa­ter sub­merges down­town, west and south Hous­ton and the Texas Med­i­cal Cen­ter.

Hous­ton’s dams were born of ne­ces­sity in the first part of the 20th cen­tury.

In May 1929, flood­ing caused $1.4 mil­lion in prop­erty dam­ages to a city of just un­der 300,000. Hous­to­ni­ans re­built and re­cov­ered, but an even big­ger storm hit in De­cem­ber 1935.

Buf­falo Bayou trans­formed from me­an­der­ing stream to roar­ing river, at one point ris­ing 14 inches an hour. Cur­rents swept away peo­ple, res­cue boats and a three-story brick build­ing at Milam and Com­merce. At the Capi­tol Street Bridge, wa­ters typically 6 feet above sea level rose to 52 feet. The storm caused eight deaths and $2.6 mil­lion in dam­ages ($45.7 mil­lion in to­day’s dol­lars) and brought the Port of Hous­ton to a stand­still.

The next year, city of­fi­cials started for­mu­lat­ing flood-con­trol plans with the Army Corps of En­gi­neers. By 1940, a $32 mil­lion plan had been re­fined to in­clude three reser­voirs — Ad­dicks, Barker and White Oak — and a levee to pre­vent Cy­press Creek from over­flow­ing into Ad­dicks. Two large canals would di­vert wa­ters from the reser­voirs north and south of down­town. Up­per Buf­falo Bayou would be straight­ened to en­able faster flow.

At the time, the Corps an­tic­i­pated most flood­wa­ters would drain within a few days.

Barker Dam was fin­ished by Fe­bru­ary 1945. Ad­dicks, ad­ja­cent to Barker, fol­lowed in late 1948. To­gether, the dams stretched for 25 miles and en­com­passed about 26,000 acres once used for ranch­ing and rice farm­ing. They were hailed as two of the long­est dams in the world.

Both in­cluded earthen em­bank­ments formed with na­tive sand, silt and clay. Each had five con­duits — open­ings through which wa­ter would be con­veyed onto con­crete spill­ways and down the bayou. De­signs called for one con­duit on each dam to have a metal gate di­rect­ing the out­put of wa­ter. The rest would be un­gated, al­low­ing wa­ter to exit un­con­trolled.

The city still faced bouts of flood­ing, but the dams per­formed as ex­pected. Homes and busi­nesses sprung up along the bayou.

“There’s a lot of things that al­lowed Hous­ton to

de­velop,” Long said. “These reser­voirs are num­ber two on the list. Num­ber one is air con­di­tion­ing.”

Over the next 50 years, de­vel­op­ment per­sisted, and the Corps found it­self un­able to con­trol what was hap­pen­ing around the dams.

The re­main­ing com­po­nents of the 1940 plan — the third reser­voir, the levee and the canals — failed to ma­te­ri­al­ize. Land costs be­came pro­hib­i­tive as peo­ple moved in.

The Corps then pro­posed deep­en­ing and lin­ing Hous­ton’s bay­ous with con­crete to al­low for the re­lease of more wa­ter, al­le­vi­at­ing pres­sure on the reser­voirs. When en­vi­ron­men­tal­ists protested, that plan was aban­doned, too, af­ter only a few miles had been lined.

Res­i­dents along the bay­ous soon grum­bled about their yards flood­ing as wa­ter was re­leased from the reser­voirs. They wanted the other con­duits gated, a move en­gi­neers wor­ried would put the dams at risk of be­ing washed away. But by 1963, the change was made.

By the 1970s, the dams were stor­ing big­ger pools, for longer, putting more stress on the foun­da­tions.

Hous­ton’s “crummy soils” didn’t help, Long said. The silt and sand used to con­struct the dams washed away eas­ily. And the reser­voirs and dams were sink­ing, a phe­nom­e­non known as sub­si­dence. Over time, set­tle­ment low­ered the tops of the dams by up to 3 feet.

In 1977, the Corps started see­ing signs of seep­age — wa­ter leak­ing into the foun­da­tions.

All dams leak to some ex­tent, but it be­comes prob­lem­atic when wa­ter erodes soil within the em­bank­ment. If enough soil gets car­ried away, it can lead to cav­i­ties and sink­holes or piping, paths that al­low wa­ter to flow freely through the dam. If enough wa­ter gets through, the dam can fail.

The Corps in­stalled miles of slurry trench, walls to pre­vent seep­age and wa­ter flow. It also raised the tops of the dams to pro­tect against a mas­sive hur­ri­cane, and put in bar­ri­ers to sta­bi­lize the em­bank­ments and screens to catch erod­ing ma­te­rial. But the trench did not ex­tend across the em­bank­ments, leav­ing ar­eas around and be­neath the con­duits vul­ner­a­ble.

Other Corps dams and lev­ees across the coun­try faced sim­i­lar prob­lems, but the agency’s short­com­ings weren’t high­lighted un­til Aug. 29, 2005.

That’s when the storm surge from Hur­ri­cane Ka­t­rina breached New Or­leans’ Corps-built lev­ees in more than 50 places. Walls of wa­ter bar­reled into roads and homes, in­un­dat­ing three-quar­ters of the city. Al­most 2,000 drowned.

Just two months be­fore Ka­t­rina, the Corps had be­gun a mas­sive un­der­tak­ing: eval­u­at­ing its hun­dreds of dams na­tion­wide. Many were at or be­yond their 50year life ex­pectan­cies. The review would iden­tify the dams most at risk and pri­or­i­tize re­pairs.

Ka­t­rina drove ur­gency and was sober­ing for an or­ga­ni­za­tion that could be over­con­fi­dent, said Jeffrey McCle­nathan, a re­tired hy­draulic en­gi­neer and co­or­di­na­tor of the Corps’ four-year review.

McCle­nathan said the Corps looked not only at the risks but also the ram­i­fi­ca­tions of failure, which it hadn’t done be­fore.

The Corps’ evo­lu­tion was a nec­es­sary and im­por­tant step, said David Bowles, for­mer di­rec­tor of the In­sti­tute for Dam Safety Risk Man­age­ment at Utah State Univer­sity. He helped de­sign a ver­sion of a pro­gram the Corps uses to model failure sce­nar­ios.

“They are now able to be so much more ef­fec­tively than the way they were be­fore,” Bowles said.

But even on dams like Ad­dicks and Barker, progress is still patch­work, and slow-go­ing.

A con­tract was awarded in Au­gust 2015 for the re­place­ment of the wa­ter con­trol struc­tures and con­duits, 400 feet from the ex­ist­ing ones. Work be­gan in Fe­bru­ary but shut down when the reser­voirs were sub­merged in April. Be­fore the de­lays, the fin­ish date was in 2019.

Af­ter Tax Day, sub­se­quent down­pours added wa­ter to the reser­voirs a half-dozen times, prompt­ing the Corps to dou­ble nor­mal re­lease rates to empty the swollen reser­voirs as quickly as pos­si­ble. The wa­ter con­trol struc­tures vi­brated as they dis­pelled murky wa­ter onto the spill­ways and down Buf­falo Bayou, car­ry­ing away trees and soil. Some res­i­dents down­stream feared the banks would com­pletely erode.

Emp­ty­ing the reser­voirs is sim­i­lar to drain­ing a bath­tub. The tub fills up. Then, the Corps pulls the stopper. The goal is to keep the wa­ter drain­ing at a steady but man­age­able rate, while never let­ting the tub over­flow.

If a big enough storm threat­ened the in­tegrity of the dams and the Corps had time to re­act, it could pull the plug, pur­pose­fully flood­ing res­i­dents down­stream. The Corps also can im­pound wa­ter on more land than it owns, so it could flood prop­er­ties be­hind or be­side the reser­voirs. Flood­ing some would be bet­ter than failure, Long said.

“We’ve got to make sure we pro­tect the city of Hous­ton as a whole,” he said.

Over the years, some ar­gued the Corps al­lowed de­vel­op­ment to go too far. In 2011, the Sierra Club sued the Corps and state agen­cies over con­struc­tion of a Grand Park­way seg­ment north­west of the reser­voirs. The com­plaint al­leged the Corps knew an­other high­way would in­crease runoff, im­pact­ing the de­te­ri­o­rat­ing dams, yet still ap­proved a per­mit for con­struc­tion — an “ir­ra­tional con­clu­sion.”

Over email, Long and Corps col­leagues pri­vately agreed more con­crete up­stream would ex­ac­er­bate ex­ist­ing prob­lems. But ul­ti­mately, Corps hy­drol­o­gists con­cluded the high­way, by it­self, would not harm the dams, with ap­pro­pri­ate drainage mea­sures.

The Grand Park­way moved for­ward, but the case may have caught lo­cal of­fi­cials’ at­ten­tion, said Jim Black­burn, an en­vi­ron­men­tal at­tor­ney who rep­re­sented the Sierra Club. He said a multi-year study on the over­flow of Cy­press Creek into Ad­dicks Reser­voir sig­naled a ma­jor step for­ward.

The study, com­pleted last Au­gust, also looked at runoff dur­ing ma­jor storms and from pro­jected growth. It es­ti­mated an­other 200,000 peo­ple would move into the area by 2060.

“It’s time for ac­tion of a type that we haven’t seen pre­vi­ously,” he said.

Based on the study, in March the Harris County Flood Con­trol Dis­trict is­sued new cri­te­ria for de­vel­op­ers in the Ad­dicks, Barker and Cy­press Creek wa­ter­sheds. Pre­vi­ous guide­lines re­quired de­vel­op­ers to ad­dress the rate at which wa­ter left their prop­er­ties, but not the vol­ume ul­ti­mately drain­ing into the reser­voirs, said Dena Green, the study’s project man­ager.

The study of­fered two ideas for tack­ling the dams’ lim­ited ca­pac­ity and re­leases. Both in­volve build­ing earthen reser­voirs to ei­ther fully or par­tially con­tain the creek’s over­flow, which sends more than 20,000 acre-feet of wa­ter into Ad­dicks dur­ing a 100-year storm.

The Corps also is look­ing to ad­dress its en­croach­ment prob­lem.

Project man­agers, in part­ner­ship with the flood con­trol dis­trict, are push­ing for a fed­er­ally funded study on the cu­mu­la­tive im­pact of land changes around the reser­voirs, and what would hap­pen if Ad­dicks and Barker be­came so full that wa­ter spilled over the sides, which came close to oc­cur­ring af­ter the Tax Day storm.

The study would in­vite longterm solutions, Long said, and “ev­ery­thing will be wide open.”

Long plans to re­tire af­ter the ma­jor re­pairs are com­pleted and leave the wor­ry­ing to some­one else.

For now, he likens the dams to a re­built car. He is con­fi­dent in re­cent fixes. But he knows there is al­ways the chance, how­ever small, that the next storm will be the per­fect storm.

Michael Cia­glo / Hous­ton Chron­i­cle

Park Ranger David Mack­in­tosh sur­veys the wa­ter level ear­lier this year from the struc­ture at Barker reser­voir that con­trols the rate of wa­ter be­ing re­leased down­stream.

“Failure is not an op­tion for us,” the Army Corps’ Richard Long says.

Michael Cia­glo pho­tos / Hous­ton Chron­i­cle

Park Ranger David Mack­in­tosh en­ters the wa­ter con­trol struc­ture on Barker reser­voir. De­vel­op­ment up­stream is caus­ing the 70-yearold reser­voir to fill up faster and hold wa­ter longer. Be­low, wa­ter flows down the spill­way of the Barker dam into Buf­falo Bayou.

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