Yes, you can test the soil for contaminants, though the lab may need an indication of what they are testing for. If you know what the trees were removed for or what was done in the area (e.g. laid cement, painted fence, etc.) that may provide some clues. Depending on what was done in the space, it is possible this could be something other than a contaminant issue. For example, if the soil was heavily compacted then that would affect the health of the newly planted shrubs. Is it possible that the irrigation system or watering was somehow disrupted? Were any herbicides or other chemicals used in the area? The more information you have or can provide, the easier it will be to narrow down the possibilities. For advice on obtaining actional results from a soil test, refer to: https://extension.oregonstate.edu/catalog/pub/em-8677-get-actionable-results-soil-plant-or-environmental-testing-lab#sampling-farms-gardens. For laboratory testing, I recommend you contact the OSU Soil Health lab in Corvallis and A&L Western in Portland to see what they can test or screen for. Also, refer to this ODA list of labs that test for heavy metals (and possibly other contaminants). Simply Soil Testing in WA also offers testing for heavy metals and specializes in testing for home gardeners (so often more affordable). 

I will answer your questions.

Compaction is certainly a possibility, especially if an excavator was rolling over or parked on top of the area. With compaction, you will often see some puddling or poor/slow drainage in that area after a heavy rain. If you have poor drainage, then Phytophthora root rot is a possibility. With Phytophthora, you would see discoloration of the foilage and eventually death. I suggest you dig down to look at some of the fine surface roots. Cut into one of the roots with a sharp knife to look at the color. If the fine roots are soft and brown and can be peeled or broken off easily, then the shrubs may have root rot. If the feeder roots are healthy, then you would see brown on the outside with a white internal core and white tips. 
In addition to Phytophthora, arborvitae are susceptible to several other diseases. If you are near Eugene, you can bring some plant samples into the Lane County Master Gardener plant clinic to take a closer look at the symptoms. You can also pay to have a laboratory analysis done at the OSU Plant Clinic in Corvallis.