* Bottom line hit by energy, Alpine writedowns
* Loss compares with small profit last year
* Ninth consecutive quarter of revenue falls
* In talks to refinance debt (Adds details and background)
MADRID, Aug 5 (Reuters) - Spanish builder FCC slumped to a 607 million euro ($806 million) first-half loss on Monday, hit by falling revenues and hefty writedowns on renewable energy assets and its Alpine unit in Austria.
Revenue at FCC, Spain's fifth-biggest builder, fell 13.7 percent to 3.1 billion euros in the first six months of the year, the ninth consecutive quarter of declines amid vanishing public-sector contracts in Spain's protracted recession.
Spain accounts for 58 percent of total revenue.
The company wrote down 207 million euros for a deterioration in the value of its renewable energy subsidy following a series of energy reforms and 372 million euros on Austrian construction unit Alpine, which went bust in June.
FCC said it burned 47.7 million euros of operating cash in the first six months of the year, while net debt fell to 6.7 billion euros at June 30 from 7.1 billion at end-December.
The debt figure does not yet reflect recent asset sales, it said.
FCC has a three-year plan aimed at reducing net debt by 2.7 billion euros by 2015 and focusing its business on infrastructure, environmental services and water management.
Chief Executive Juan Bejar, who was hired this year to revamp FCC after years of falling profits, said in July that the builder would complete a debt refinancing by October.
Shares in FCC, which have gained 21 percent so far this year on hopes for a company turnaround under Bejar, were flat at 11.305 euros at 0715 GMT.
$1 = 0.7528 euros Reporting by Tracy Rucinski; Editing by Paul Day and Mark Potter