The massive road widening project 3 country blocks from our home precipitated the migration that we were witnessing. The major excavation is done, so we hope to be through the worst of it.
Vigilantly patrolling areas of sightings with nasty spider poison did help, but we had to spray directly on the critters. At our house they hung around under one window and all around the front door. Fortunately we could check out the exterior doorway from the dining room window. I'm certainly not brave enough to step out of a door and not know where the enemy is.
Any spider bomb type responses would have been a poor choice as they don't harm tegenaria agrestis and they do take out all the other spiders, potential combatants and potential food competition.
When other spiders return, rejoice and leave them be. This is really hard for me, but as long as there is a non-tegenaria agrestis spider living on my front porch, I can be sure that there is not an evil spider, as the evil ones are turfy and would dispatch the competition right away.
For more info on these truly nasty spiders, who -- despite what my Dad would try to tell me -- really do want to bite me, visit the Oregon Department of Agriculture fact sheet on Tegenaria Agrestis.