Rehabilitation of Lashis-Gele Water RC Reservoir, Existing Conditions

2.  Original Design of Rehabilitation of existing RC drinking
water reservoir considered cleaning of the reservoir,
removal of old plaster and “ironing” of the walls, plastering
of inner roof slab surface.
 After the entry to washed reservoir where deposited sludge
has been removed, disturbing existing conditions have been
revealed. What came immediately to attention is bunch of
roof slab reinforcement hanging like spaghetti from the roof
slab, deteriorated from corrosion during constant exposure
to high humidity where no concrete cover was provided
during original reservoir construction. Roof slab
reinforcement was ~70% exposed, visible. Previous attempt
of exposed reinforcement protection was visible where
plastic foil tapes were applied directly over the
reinforcement. Holes present in roof slab concrete from
where rain, bugs, small animals could easily enter the
reservoir. Multiple orange stains on the inner walls
indicating serious leaking of the reservoir walls where high
level of underground water managed to enter the reservoir.
Walls were multiple times coated by all types of hydro-
plaster, failing to seal the walls, concrete deteriorated on
water entry points. Columns made of oversized aggregate
concrete with exposed reinforcement on some sections.
Uneven, unlevelled base slab surface with spilled concrete
from previous “rehabilitation projects”.
 With coordination of Employer and Designer, scope of works
has been changed and extended where a New Design
consisted of removal of existing roof slab and part of walls –
so that new reservoir could be built inside of the existing
reservoir shell. Considering doubtful structural stability of
vibrating roof slab, no-entry has been declared due to H&S
reasons. Demolition of the reservoir’s roof slab exposed that
roof slab thickness was 8-10cm with deteriorated & corroded
reinforcement (only 1 layer), bars were not even lapped and
those which were attempted to over-lap had no contact with
each other. Only plain bars were used, no ribbed bars! During
walls plaster removal - 5-6 layers of plaster were detected
whose removal exposed that during original construction
some 20yrs ago – no water stop was used between
horizontal 1.0m high layers of concrete installed in walls, next
wall-layer of concrete installed directly over the joint from
previous layer without any water-stop used. Water has easily
found its path throughthese cold-joints. By revised Design,
reservoir has been demolished (roof slab & part of walls), its
shell used as a "lost formwork" for construction of new
reservoirs inside of existing reservoirs.