Sump holes should be fitted with covers which have weather stripped holes only large enough for the various protrusions (pipes, wires, etc.) through them. Three-quarter-inch plywood makes a good cover and if the necessary holes are drilled in a straight line, the plywood can be cut to fit around all the protrusions, the edges of it properly weather-stripped and put in place. This keeps an otherwise large surface of water from evaporating into the basement and substantially raising humidity levels there.
