As per your request here is some of the govt. PSU which offers jobs to civil engineer diploma students.

Government Public Sector Unit (PSU) Companies appoints fresh and experienced Diploma Holders in various engineering fields: Electrical, Mechanical, Electronics, Civil, Computer Science, Electronics & Communication and Chemical Engineering.

General Qualification: Three Years full time Diploma in engineering discipline from AICTE / Govt. approved Institutions and Universities.

Civil Engineers have huge opportunities in the:
Indian Railways
Air ways
Roadways
And many Government owned companies like :
BHEL
BEL
NTPC
Coal India
HPCL
Airport Authority of India
IIT institutions
ECIL
BPCL

Government PSU like:
UCI
NACL
NLC
SAIL
NTPC
IOCL
ONGC
Power Grid
Railtel
NMDC
RITES.

Currently the following are the current opening in the following organizations:

Nagaland Public Service Commission (NPSC)
Paradip Port Trust
MIDHANI
Bharat ElectronicsLimited
BWSSB
MPSC
IRCON
CPCB
CDFD Hyderabad
CCRS
NIRM
InstrumentationLimited
Vasant Kanya Mahavidyalaya
Vehicle Factory Jabalpur
ASC Centre (South) Bangalore
RPGMC
Sahitya Akademi
SSCBS