CAMBRIDGE, MASS. — Locally based firm Nauset Construction is underway on the renovation of a 90,000-square-foot data center that is located across the Charles River from Boston in Cambridge. The project represents the third phase of capital improvements at the property at 300 Bent St. Upgrades will include the demolition and excavation of the existing lobby, the revamping of mechanical and utility systems and the addition of another 8,000 square feet of tenant space. Khalsa Design is the project architect. Construction is anticipated to be complete this fall. CEM Realty Trust owns the property.