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duration o f each pressure te s t s h a ll be at le a s t 30 minutes. A l l exposed pip es, f i t t i n g s , v a lv e s , hydrants and jo in ts w i l l be c a r e fu lly examined during the open trench t e s t . Where the jo in ts are made w ith sulphur compound and show seepage or s lig h t leakage, only such jo in ts as may be d e fe c tiv e sh a ll be cut out and replaced as d ire c te d by the Engineer. Any crack­ed or d e fe c tiv e pipes, f i t t i n g s , v a lv e s or hydrants d isco ver­ed in consequence o f th is pressure t e s t s h a ll be removed and replaced by the Contractor with sound m a teria l and the te s t s h a ll be repeated u n til s a tis fa c to r y to the Engineer. B a c k fill S elected b a c k fill m a teria l fr e e from rock or boulders s h a ll be deposited in the trench simultaneously on both sides o f the pipe fo r th e f u l l w idth o f the trench and to an e le v a ­tio n o f not le s s than 6 inches above the h o rizo n ta l center lin e o f pipes w ith diameters 12 inches or la r g e r , le a v in g the jo in ts exposed f o r examination during the pressure t e s t . The b a c k fill m a teria l s h a ll be thoroughly compacted under and on each side o f the pipe to provide s o lid backing against the extern al surface o f the p ip e. Succeding la y ers o f b a c k fill may contain coarser m ateri­a ls , and s h a ll be fr e e from brush or any other perishable or ob jectio n a b le matter th at would prevent proper con solid ation or that might cause subsequent settlem en t, and s h a ll be com­pacted thoroughly by puddling w ith hose and long n o zzle , or by flo o d in g the trench, or by tamping i f the m aterial does not puddle r e a d ily . A fte r h y d ro sta tic t e s t has been made as s p e c ifie d and pipe is f u l l o f w ater, the pipe s h a ll be tapped at in te r v a ls as d irected by the Engineer fo r the purpose o f providin g water fo r trench flo o d in g . Contractor s h a ll fu rn ish la b o r, m ateria l and to o ls f o r th is work. I t is important th at proper precautions be taken to prevent flo a t in g o f the pipe when flo o d in g th e.tren ch , and the Con­tra c to r s h a ll be w holly resp on sible fo r n eg lect o f these precau tion s. No rock or boulders s h a ll be used in the b a c k fill fo r at le a s t one fo o t above the to p o f the pipe. R estora tion o f Surface The Contractor s h a ll re s to re a l l paving, curbing, s id e ­walks and g u tters, in accordance w ith s p e c ific a tio n s and to the s a tis fa c tio n o f State o f Nevada Highway Department and the C ity o f Las Vegas, and s h a ll rep lace a l l shrubbery, fen ces, sod, and other surfaces disturbed, to a con dition equal to that b efo re the work began, fu rn ish in g a l l labor and m a teria l In cid en ta l th ere to . In r e s to rin g paved surfaces new pavement is req u ired . No permanent paving sh a ll be p la c ­ed w ith in 30 days a ft e r the b a c k fillin g s h a ll have been -4 -