** Shares of WestStar Industrial WSI.AX rise as much as 73% to A$0.099, their biggest intraday pct gain since March 31, 2017

** Stock hits its highest level since February 14

** The construction and engineering co's unit wins A$115 million ($75.80 million) procurement and construction contract

** Contracts include civil works, others at Alcoa Pinjarra alumina refinery in Western Australia

** About 14.9 million shares traded in stock's busiest day since July 30, 2019, 119.5x the 30-day average

** YTD, stock down 19%, including current session's move

($1 = 1.5172 Australian dollars)

(Reporting by Ananya Verma in Bengaluru)

((ananya.verma@thomsonreuters.com;))