Dogfish - That is correct.
The WDFW carefully considers the spawning cycles of all fish in the subject stream and they set the work window that we must work WITHIN. We are allowed to work only before the fish spawn. Additionally we work in different areas of the stream, not in the spawning beds.
HPA's can be requested by filing a JARPA pr Joint Aquatic Resource Permit Application. This is a Department of Ecology instrument and there are 7 versions and/or addendum's depending on what you are wanting to do. The base permit application is 14 pages. After the JARPA is reviewed the Hydraulic permit may be denied (happens a lot, several times to me personally) or it may have detailed stipulations. It requires a in person site visit with the biologist who considered all possible fish impact of this particular project and issues the permit with appropriate restrictions to protect fish and habitat.

On one of my HPA sites, the biologist was very cautious about habitat protection. I invited him to my claim to observe my dredging activity and help him understand how benign the impact actually was. He learned a lot and had a good time.