The contractor that remediates this will definitely have their hands full (and the home owner probably a large bill). They’ll have to dig it out before they can even get to thinking about cleaning; and, they’ll have to do it in a way that prevents any cross contamination. I’ve worked on projects like this in the past. While demanding, they can be very rewarding when completed. As a Council-certified Indoor Environmental Consultant, I generally recommend to my Clients that when remediation is performed that moisture preventing measures be taken to avoid future reinfestation and contamination, a system that addresses thermal properties, humidity, plumbing leaks and other unforeseen disasters, and ventilates the crawl space so that air can be properly moved and processed (for example dehumidifier or air purifier or HVAC system with a good filtration system) - all specific to the structure. (I’m not trying to sell any one procedure over another in this post.) Failure to make sure that moisture is controlled may hinder remediation ineffectiveness and reinfestation can occur (all of this without mentioning the other microbes and parasites that flourish in a moist environment such as this and their effects on the building, its system, and the indoor air quality).