Bal­anc­ing act needed in new build­ings

Con­trac­tors strive to save H2O, but must be aware that non-potable wa­ter may be un­suit­able

Weekend Argus (Saturday Edition) - - PROPERTY - BONNY FOURIE

CAPE Town’s con­struc­tion in­dus­try is be­ing hit hard by the city’s wa­ter cri­sis as con­trac­tors seek al­ter­nate wa­ter sources in their daily de­vel­op­ment and build­ing work.

Not only does this in­cur ex­tra costs and lo­gis­ti­cal plan­ning, but the Master Builders As­so­ci­a­tion Western Cape warns that wa­ter from these al­ter­nate sources could pose health, safety and en­vi­ron­ment risks if the qual­ity is not prop­erly checked.

The in­dus­try is work­ing hard not only to re­duce its wa­ter us­age, but also to con­struct homes that will re­quire less wa­ter.

The Green Build­ing Coun­cil of South Africa says the built en­vi­ron­ment cur­rently ac­counts for 20% of the world’s potable wa­ter us­age, and green build­ings can save be­tween 20% and 100% of the potable wa­ter a con­ven­tional build­ing would use.

With sav­ing this wa­ter a “ma­jor pri­or­ity” in the Western Cape, Man­fred Braune, ex­ec­u­tive di­rec­tor of cer­ti­fi­ca­tions at the coun­cil, says green build­ings are prefer­able as they are de­signed and built to save re­sources.

“In some cases, build­ings can be de­signed and op­er­ated to be net pos­i­tive wa­ter (gen­er­ate more wa­ter than they use) and these of­fer ben­e­fits to the greater com­mu­nity.”

Both new and re­fur­bished homes can tar­get wa­ter ef­fi­ciency.

“All build­ings can be retro­fit­ted with wa­ter-sav­ing de­vices such as dual flush toi­lets, low-flow san­i­tary fit­tings, rain­wa­ter-har­vest­ing tanks and grey wa­ter sys­tems.”

When build­ing homes, prop­erty de­vel­op­ers and builders should also in­ves­ti­gate Al­ter­nate Build­ing Tech­nolo­gies, as some use less wa­ter dur­ing con­struc­tion than tra­di­tional ma­sonry.

They should also, wher­ever pos­si­ble, use re­cy­cled wa­ter in­stead of potable wa­ter on site, he says.

Build­ing sites must be man­aged to en­sure wa­ter used for con­struc­tion pur­poses is “tightly con­trolled”.

For some time the City of Cape Town’s wa­ter re­stric­tions have out­lawed the use of potable wa­ter for wash­ing hard sur­fac­ing and paving, says Allen Bodill, ex­ec­u­tive di­rec­tor of the Master Builders As­so­ci­a­tion Western Cape.

This has pre­sented “se­ri­ous chal­lenges”, par­tic­u­larly topaint­ing, dec­o­rat­ing and paving con­trac­tors.

Bodill says it was com­mon prac­tice in the past to pre­pare ex­ist­ing build­ings for re­paint­ing by us­ing high-pres­sure wash­ing equip­ment on wall and roof sur­faces to re­move loose and flaky ma­te­ri­als, but this is ob­vi­ously a wa­ter-in­ten­sive op­er­a­tion.

Peo­ple have had to use al­ter­nate wa­ter sources, such as bore­hole and har­vested rain­wa­ter and re­cy­cled ef­flu­ent or nat­u­ral spring wa­ter for these tasks.

“This sig­nif­i­cantly in­creases the cost and lo­gis­ti­cal ar­range­ments to source, store and trans­port this wa­ter to site dur­ing the prepa­ra­tion phase of this type of work. Con­sid­er­a­tion and care also needs to be given to dis­charg­ing some grades of re­cy­cled ef­flu­ent wa­ter into the mu­nic­i­pal storm wa­ter sys­tem, as there may be po­ten­tial risk of con­tam­i­na­tion to the en­vi­ron­ment.”

In ad­di­tion, de­pend­ing on the chem­i­cal com­po­si­tion of the al­ter­na­tive wa­ter and its com­pat­i­bil­ity with the ma­te­ri­als used in the re­dec­o­rat­ing pro­cesses, there could also be other risks.

“Some of these wa­ter sources may con­tain min­er­als and pathogens in so­lu­tion which may pose both health and safety risks to the con­trac­tor’s staff, as well as pre­sent­ing pos­si­ble paint ad­he­sion risks.”

As con­struc­tion is broadly de­fined as a moderately wa­ter-in- ten­sive in­dus­try, Bodill says site oper­a­tions such as dust sup­pres­sion, clean­ing of build­ing sites, struc­tures and con­trac­tors’ plant and equip­ment, as well as wa­ter sup­plies to tem­po­rary site ablu­tion fa­cil­i­ties should now all be car­ried out us­ing al­ter­na­tive wa­ter sources.

How­ever, struc­tural con­crete and ma­sonry el­e­ments of the build­ing have to be “very care­fully eval­u­ated” when con­sid­er­ing the use of al­ter­na­tive wa­ter sources in their con­struc­tion. This is due to the pos­si­ble dan­gers as­so­ci­ated with con­tam­i­nants in these al­ter­na­tive wa­ter sources which may re­sult in prob­lems of dura­bil­ity and the struc­tural strength of these el­e­ments.

“The pro­fes­sional teams over­see­ing the de­sign and erec­tion of these struc­tures should closely mon­i­tor and ap­prove the wa­ter qual­ity used on site for build­ing these el­e­ments.”

When de­sign­ing and build­ing new struc­tures from scratch, he says the op­por­tu­nity ex­ists to in­stall the plumb­ing in that will sep­a­rate the potable sup­ply fit­tings from a pos­si­ble al­ter­na­tive wa­ter source, which could be used to sup­ply toi­lets, gar­den taps, wash­ing ma­chines and other non-potable needs.

In ad­di­tion, a com­mon ap­proach is to in­stall a well-point or bore­hole on the site, where fea­si­ble and af­ford­able, and then to care­fully an­a­lyse and fil­ter the wa­ter be­fore pump­ing it into the do­mes­tic retic­u­la­tion sys­tem.

“It is very im­por­tant to es­tab­lish the pH lev­els of this ground­wate. Should this be ex­ces­sively cor­ro­sive, it could re­sult in a costly fail­ure of com­po­nents in hot wa­ter cylin­ders, ket­tles, wash­ing ma­chines and cop­per pipes and fit­tings.”

In­stalling rain­wa­ter-har­vest­ing com­po­nents as well as grey wa­ter sys­tems on new struc­tures, and retrofitting these to ex­ist­ing build­ings, will all help to re­duce the de­mand on the potable wa­ter re­source, Bodill says.

“While op­por­tu­ni­ties ex­ist to go par­tially or com­pletely off the City of Cape Town’s potable wa­ter grid when con­struct­ing new build­ings, or when retrofitting these to ex­ist­ing build­ings, there are a num­ber of risk fac­tors which need to be con­sid­ered.”

There have also been sug­ges­tions that the City of Cape Town should halt all build­ing de­vel­op­ment un­til the worst of the drought cri­sis is over.

Re­spond­ing to this rec­om­men­da­tion, Mayor Pa­tri­cia de Lil­lie says the city must bal­ance very im­por­tant con­sid­er­a­tions and save wa­ter while, at the same time, not com­pro­mise the eco­nomic wel­fare of Cape Town.

“De­spite our steep pop­u­la­tion growth since 1996, our wa­ter de­mand has re­mained rel­a­tively flat due to mas­sive con­ser­va­tion ef­forts. Our Wa­ter By-law has been a pro­gres­sive piece of leg­is­la­tion that has been one of the key tools used to guide wa­ter de­mand and con­ser­va­tion ef­forts over the years.

“The city has there­fore had pro­gres­sive by-laws, smart-liv­ing guide­lines and wa­ter-con­ser­va­tion pro­grammes in place for decades. We are cur­rently see­ing how we can en­hance our ef­forts to be­come a more re­silient city.”

PIC­TURE: SEEFF

De­vel­op­ers em­bark­ing on con­struc­tion projects, like the El­e­ments on Main and El­e­ments on Bat­tery in Sea Point, are fo­cus­ing on wa­ter preser­va­tion.

PIC­TURE: CITY OF CAPE TOWN

The Bel­har Gar­dens so­cial hous­ing de­vel­op­ment was re­cently recog­nised for de­sign ex­cel­lence in greater wa­ter and en­ergy ef­fi­ciency.

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