This large six-cell storm water detention vault incorporated both hollow core slabs and precast solid slabs. Three of the cells were designed as sand filters that required the lid to be completely removed for maintenance. Hollow core slabs are not a removable lid solution as the longitudinal keys between adjacent hollow core slabs must be filled with grout to fully develop the concentrated load distribution and shear friction capacity of the system. Therefore, removable precast solid slabs were used for the sand filter lid structure. The lid for this large vault consisted of 221 pieces of 12 ½” thick x 4’ wide prestressed, precast untopped hollow core slabs and 107 pcs of 10” thick x 5’ wide precast solid slabs. The hollow core slabs and precast solid slabs reached span lengths of up to 23’-6” and 14’-6”, respectively.
