A device used to manage the movement of surface water into and out of an attenuation facility. Drainage which runs through pipework installed to a fall, and not therefore under pressure. Water that is below the surface of ground in the saturation zone. Will not allow water to pass though it.
Examine your crawlspace from both the inside and outside and find all holes and entrances into the space. If your crawlspace is reasonably dark, going inside, turning off the light and looking for sunlight coming in from outside is a great way to do this. Seal the holes with expanding foam or caulk.
Building codes require that crawl spaces be made accessible.The 2012 IRC describes the minimum crawl space accessibility requirements as follows: R408.4 Access. Access shall be provided to all under-floor spaces. Access openings through the floor shall be a minimum of 18 inches by 24 inches (457 mm by 610 mm).