Shut all electricity and gas off to the basement if possible. Call the fire department and ask for a safety inspection. Phone your insurance agent or company as soon as the apartment is flooded. If it is safe to enter the area, put on hip waders and/or rubber boots. Go into the basement and take pictures of the damage. Make a written list of all items in the apartment to submit to the insurance company.
Set up a sump pump and siphon out all standing water. Use a shop vacuum to take up any remaining pools of water the sump pump did not siphon out. Open the basement floor drain, if applicable. Sweep toward the drain with a push broom. If your apartment basement does not have a drain, use the shop vacuum.
Place several portable fans in the space and a dehumidifier to dry the moisture and prevent mildew, bacteria, and mold growth. If it is bright and sunny outside, open the door and windows to allow sunlight in to help dry out the basement.
Put on heavy-duty work clothes and gloves. Remove belongings from the basement. Have a friend or family member help to lessen the strain of lifting water-soaked furniture and personal belongings out of the apartment. Lift with your legs, not your back, when removing items.
Separate salvageable items from non-salvageable items. Most wood furniture can be sanitized with bleach and water, while items such as books and clothing should be discarded.
Put on a dust mask. Pour 5 gallons of distilled water into a large bucket, then add 1 cup of bleach. Wipe down the walls and floors with the solution, using sponges; do this twice to sanitize the space and prevent mold, mildew and bacteria growth. Allow the portable fans and dehumidifier to run for at least 24 hours.