Page 88 - Water Standards

7.1.19 Themeasuresforsee p a g econtrol ,draina g eandmois-
turep roofofmaincavernsformainp owerhouse ,maintrans-
former ,hi g hvolta g eswitch y ard,etc.,shallbedetermined
basedonlocalg eolo g icalconditions , h y drolo g icalconditionsand
p ro j ectla y outandconformwiththefollowin g s :
1 Forcavernclosetothereservoirorrivercourseorinthe
areawithabundantg roundwater ,see p a g econtrolanddraina g e
shallbeintensifiedatitsfrontsideandrivercourseside.Ifnec-
essar y imp erviouscurtainanddraina g etunnelsma ybep rovid-
,
edatdifferentelevationsoutsidetheclusterofcavernsandat
theto pofp owerhouse,anddraina g ecurtainsma ybep rovided
indraina g etunnelstoformadraina g es y stemoutsidethep owe-
rhouse.
2 Intheareawithabundantg roundwaterorrockmassof
,
hi g hp ermeabilit y thedraina g es y stemoutsidethep owerhouse
shouldbeformedbeforetheexcavationofmaincaverns.
3 Whentailracesur g echamberisp rovided, thesee p a g e
controlanddraina g eonthecavernsideclosetothetailracesur g e
chambershallbeenhanced.
4 Gravit ydraina g eshallbeado p tedwheneverconditions
arep ermitted.
5 Ifp ump eddraina g eisneeded, theq uantit yofleaka g e
shallbedeterminedaccordin gtotheh y dro g eolo g icalconditions
ofsurroundin grocks ,see p a g econtrolanddraina g emeasures ,
andatthesametimecollectionwellsanddraina g ep ump in gfacili-
tieswithade q uateca p acit yshallbep rovided.
7.1.20 Theg eolo g icalex p lorationadits , testtrenchesorother
p
wells ,itsandconstructionaditsthatma ycausewatertoflow
intotheunder g roundp owerhousedurin gconstructionoro p era-
tionshallbep lu gg edsafel yandeffectivel y.

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