I've mentioned before that I enjoy editing technical writing - making something horribly dry and boring at least readable. I've discussed many pet peeves - abbreviations (here and here), repetitive sentence structure, citations... but I come across so many that I am compelled to share more.
So, one of the things that kills technical writing is the passive voice. Nothing puts the reader to sleep faster than having to read long, complicated sentences (buried in even longer paragraphs!) in which nothing happens.
The problem is that most geological reports are inherently descriptive. You have a study area/environmental site that just sits there and doesn't do anything. Ok, all sorts of fascinating stuff is happening on geological and microscopic scales, but those processes are seldom the focus of the report. The report is just supposed to Say What's There.
So writers tend to use a lot of "there is stuff here but not there" and "the stuff is located/situated in this particular place". You can get a little creative and mix in active words as appropriate. For example, a stream can flow or continue in a particular direction, a fence can cross a particular area, and various critters of ecological interest can burrow, stray into, and thrive in your study area. Figures depict, tables summarize.
One thing you shouldn't do in a report is favor readability over precision or responsibility. Something was only encountered if someone actually, you know, ran into it. Another issue can come up when making a description active - you may induce a lot more specificity into something that you really should keep general. For example, a whole bunch of samples were analyzed by someone or other, but writing that Lab X analyzed everything may not be technically correct (are you sure that over the 5-year monitoring period, the samples didn't go somewhere else?) and put the focus on the wrong thing - the mechanics of the analysis instead of the results. And sometimes things were done that you really don't want to own or imply that someone else should.
The other thing you can't do is stretch verbs to subjects that don't work. For example, lots of things can occur. But only events. Animals may appear from time to time, and that may be a (small) event for your site, but they don't occur spontaneously - they arrive there by some means or another.
One caveat: It doesn't take much sprinkling of active verbs to liven up a report. You don't have to tie yourself in knots to rid yourself of every passive verb. But just a few adjustments will make a routine report much less painful.