Abstract: A lightweight composite concrete cover is provided for subgrade trenches and vaults. The lightweight cover comprises at least one low density layer that has a low density filler material such as polyethylene terephthalate beads. The low density layer substantially reduces the overall weight of the cover, and the remaining layers provide sufficient structure for the cover to pass rigorous load and chemical exposure testing. In addition, a method of manufacturing a lightweight cover is provided that promotes the combination of different layers of the cover and the cross linking of polymer chains between layers of the cover. The lightweight cover has substantial weight savings and also meets rigorous testing standards such that a worker can manually remove the cover, transportation costs are realized, and worker safety is improved.

Abstract: A vault system is provided that defines an enclosed volume to protect various electrical, water, communications and other components. The system comprises a lid to allow selective access to the contents in the enclosed volume of the vault. Over time, continued wear and tear on the lid of the vault can cause the lid to deflect inward and/or cause the body of the vault to deflect outward, which compromises the integrity of the vault. Interlock features, methods, and systems are provided transfer stress and strain between the lid and the vault, which maintain the integrity of the selective interconnection between the lid and the vault.

Abstract: A vault system is provided that defines an enclosed volume to protect various electrical, water, communications and other components. The system comprises a lid to allow selective access to the contents in the enclosed volume of the vault. Over time, continued wear and tear on the lid of the vault can cause the lid to deflect inward and/or cause the body of the vault to deflect outward, which compromises the integrity of the vault. Interlock features, methods, and systems are provided transfer stress and strain between the lid and the vault, which maintain the integrity of the selective interconnection between the lid and the vault.