A hairpin turn on Lucas Valley Road will be realigned this summer to soften a curve that has been the site of numerous accidents. Just east of the Big Rock trailhead, the Department of Public Works will install a 135-foot retaining wall, allowing the road to shift out from the hill and a guardrail to be added. A traffic study found that from 2004 to 2014, 17 people were severely injured in crashes along the…