Considering how long the plant has been there (since 1906), the probability of expensive-to-remediate contamination is high. On the plus side, it didn't burn coal for that whole time: conversion to coal and construction of the present plant didn't happen until the late 1970s (along with the fairly spectacular demolition of the landmark smokestack from the old plant). Of course, the heavy oil used previously was probably pretty high sulfur and full of other interesting things that got spread around, especially during the less-environmentally-conscious early part of the 20th century; since emission controls came along with the coal burning, it was a net improvement for air quality at the time.

For those who like Google satellite views, here's the plant: [www.google.com]

In addition to the railroad line out of Santa Cruz, the old plant had an extensive narrow-gauge system into the San Vicente Creek limestone quarries. In the 1970s, they shifted their quarry operation to the Bonny Doon area, with one of the longer conveyor belts around to connect it with the plant.

Here's the main San Vicente Creek quarry: [www.google.com]. If you look very carefully, you can see slight traces of the old n.g. r/w.
And here's the main Bonny Doon quarry: [www.google.com]. The conveyor belt line to the plant is obvious.

The Santa Cruz area has an interesting railroad-related history that's worth looking at. It's pretty well documented in books, and more recently of course in Howard's fine photos.