SGH completed an emergency evaluation, oversaw an underwater inspection by our subconsultant, and observed the culvert blocked with debris and a large void under the southbound roadway lane. We advised the DCR that potential for flooding and failure of sewer and gas lines, along with the need for emergency access, made the culvert a public safety hazard. Since closing Speen Street would significantly affect area traffic, SGH designed an emergency replacement of the culvert.
We worked closely with the DCR, the Town of Natick Board of Selectmen and Conservation Commissions, and utility companies. SGH presented the project details and schedule to the public. On behalf of the DCR, we also applied for and were granted an emergency environmental certification, avoiding lengthy Notice-of-Intent permitting processes.
SGH designed a double-barrel precast concrete box culvert with two, 6 ft by 10 ft hydraulic openings. Our design included erosion and sediment control measures on both the upstream and downstream sides of the culvert prior to construction. Loose soil conditions complicated design and construction. To address the sandy soil, the project team implemented a steel, sheet-pile cofferdam, a tremie concrete seal, and a driven pile foundation for permanent support. The contractor installed diversion pipes under the road north of the culvert replacement to maintain water flow during construction.