AstroTurf, the manufacturer of the nest pad material, recommends soaking the pad in water with a mild soap (like hand dishwashing soap).   A good way to do this is to roll up the nest pad and put in a standard 5 gallon bucket, fill it with water and soap, and let it soak for a day or two.  After soaking, gently rinse the nest pad to remove any debris.Using a pressure washer is not recommended because it may cause unneccesary wear on the pad resulting in tearing.