A locking security lid incorporates a cylindrical housing having extendable pistons and contact pads for contacting the interior surface of an access pipe, the contact pads may be retracted to a withdrawn position wherein the contact pads are within the outside diameter of the cylindrical housing. The cylindrical housing is provided with a locking bolt to will be secured to the cylindrical housing through a stanchion and having a keyed bolt head to prevent removal of the locking bolt without a socket wrench having a corresponding slot pattern. The contact pads are provided with a locking interference surface to prevent relative movement between an access pipe and the contact pad when the contact pads are extended.