One Day Under the Grass - Charlton Baer

When Hooker is called out to two a car out of the south San Francisco Bay, it doesn't turn out the way he expected. When the assisting cop pulls up the first head, they know it's a crime scene. When the dive team keeps finding bodies or skeletons, they know it is a dump site for a serial killer.

A driver's license leads them to the night streets of San Jose and disappearing streetwalkers. 

Soon, it becomes very personal to Hooker, and friends of his. He needs help and consults with the best expert he knows about the marshes of the south bay—his sister. 

As the killer steps up their game, Hooker finds himself in an all-out battle to stop the killer.