I have a herniated lumbar disc. Will I be able to continue heavy construction after treatment?

Depends. It will vary depending on your age, fitness and symptoms. If you have good core muscle strength (tummy and back muscles), good aerobic (heart-lung) fitness, good body weight (not over or under weight) you may be able to return to work one the leg pain/symptoms subside. Most folks are unable to do heavy labor at some point in time as they age, but this does vary from person to person.
Yes . 90% heal without surgery and allow for full return of activities once asymptomatic. To minimize recurrent issues, don't smoke, exercise regularly and keep trim in terms of weight. Even if surgery is need, there is a 90% success rate with return to all activities once 12 weeks after surgery.