HDD Design for Construction Ocean Outfall

The City of Rehoboth Beach is required, under the terms of a consent order from the Dept. of Natural Resources, to eliminate the discharge of treated effluent from the Rehoboth Beach Wastewater Treatment Plant into the Lewes-Rehoboth Canal. The city, after detailed studies and the evaluation of all options, proposed an ocean outfall in order to comply with that order. On August 14, 2017, the Rehoboth Beach Commissioners unanimously approved awarding four bid packages to various contractors to begin construction on the ocean outfall project. The four bid packages were treatment plant improvements, effluent pump station, on-shore pipeline, and offshore pipeline including a diffuser to comply with the consent decree. This paper will discuss the purpose and design of the project including pipeline routing, construction alternatives, regulatory requirements, the construction season, and environmental concerns. The project design included pipeline routing, construction alternatives, and regulatory requirements. One of the biggest impacts to the project was the proposed construction season requiring the marine work to be completed in winter and the system operational by June 30, 2018. The winter of 2017–2018 was most notable for four nor’easters in March, which directly affected marine construction. The paper will conclude with a brief summary of construction details from the actual construction of the 6,000 feet of outfall including diffuser. Horizontal directional drilling was used to complete 3,800 feet of the outfall. Construction of the marine outfall commenced November 2017 and was completed before the June 30, 2018, deadline.