4 20 ex c a v a tion 1 S t ake out and exc a v a te in ac c o rdanc e with OSHA regula tions to elev a tions per appro v ed plans E x c a v a tion R equirement s a R e c c omended S ubgr ade exc a v a tion is a minimum o f 6 152 mm belo w designed Module inv ert I A 4 102 mm lev eling bed may be ac c e p t able c o nt ac t y our S t ormT ank R epresent a tiv e f or further det ails b T he exc a v a tion should extend a minimum o f 12 305 mm bey ond the module unit s dimensions in each length and width to allo w f or adequa te plac ement o f side back ll ma terial c R emo v e objec tionable ma terial enc ountered within the exc a v a tion including pro truding ma terial from the walls 30 subgrade prep ara tion 1 U n st able unsuit able and or c ompromised areas should be br ought to the E ngineer s a t tention and mitiga ting ef f o rt s determined S ubgr ade shall be unfro z en free o f lumps or debris and c o nt ain no st anding wa ter or mud 2 S ubgr ade must be prepared per the E ngineer o f R e c o rd to pro vide a minimum bearing c a p acity and prev ent settlement a Maximum applic able settlement s c anno t exc eed long term 12 127 mm dif f e rential settlement betw een any tw o adjaent unit s within the s y s tem b S ubgr ade must be designed to ensure soil bearing c a pacity is maint ained throughout all soil sa t u r a tion lev els