Here is the full statement from SMRT:
To facilitate the continued acceleration of the power cable change
currently undertaken by the Land Transport Authority (LTA) and
SMRT, some service changes will take place on the Circle Line (CCL)
on two Sunday mornings in May 2013.
On Sunday 12 May, Marymount and Caldecott stations will operate
with a single platform from 6 to 10 am. Trains going in either
direction will stop at the same platform, as the other side is
closed to enable cable change works.
A similar arrangement will take place at Botanic Gardens and Farrer
Road stations from 6 to 10am on Sunday 19 May.
During these periods, there will be signs put up at the affected
stations to inform passengers of the change in the platform
arrangements. At the same time, we will be making announcements at
the stations and in the trains, to alert passengers of the
diversions. We will also deploy some of our staff to guide
passengers on the ground.
Passengers may be inconvenienced with an addition of up to 10
minutes in their travelling times. We ask for their understanding,
and advise them to adjust their travelling times accordingly.
source