Background

The Sunset Beach Sanitary District (District) was formed in 1930 to provide sanitary services to an approximately 175-acre area primarily comprised of the Huntington Beach community of Sunset Beach, and the Seal Beach community of Surfside Colony. The community is located on a low-lying, relatively narrow strip of land between two water bodies – with the ocean to the southwest and Huntington Harbour to the northeast. Due to its low-lying location between the oceanfront and the harbor, Sunset Beach has historically been subject to flooding and damage during storm conditions. Flooding of areas along Pacific Coast Highway from Huntington Harbor occurs in Sunset Beach now with extreme high tides. Flooding from the harbor inland of the subject site may occur earlier than beach flooding.

The pump station is located within and along the inland side of Greenbelt Park and parking area, under the street, and has been in operation since 1935. It receives sewage from 3 incoming sewer lines and pumps that sewage into a pressure pipe that delivers the sewage to Warner Avenue at PCH.

Situation

The District wishes to abandon the existing pump station to eliminate their single largest sewage spill risk, a risk that has been recently exacerbated by climate change impacts. Eliminating the only operating pump station will provide significant annual cost savings to the District in lowered electricity and pump station operations’ costs. The District’s alternate option of replacing it with a new above ground pump station and pressure pipe is costlier and does not eliminate the pump station operations and maintenance cost component.

Challenges

One of the main challenges with this project was the extensive coordination with all stakeholders. LEE + RO assisted the District with coordination and meetings throughout the preliminary and final design phases to obtain the following permits:

• City of Huntington Beach encroachment permit – Per the City requirements, work can be performed from Labor Day 2024 to Memorial Day 2025. The City has agreed to use a portion of the parking lot as a staging area for the duration of the project. A total of 10 trees will be replaced with 20 trees per landscaping plans. The Contractor will prepare and submit a Groundwater Dewatering Plan, and a Subsidence Monitoring Plan to the City of Huntington Beach Public Works Department and obtain approval prior to the start of any work.
• Caltrans Encroachment Permit – Caltrans permit requires night work on PCH at Warner Avenue.
• Coastal Development Permit from California Coastal Commission – There are three (3) special conditions that require compliance: a) Pre-construction nesting bird survey - The Contractor must schedule work to avoid conflict with the nesting season of February 1 to September 1 or comply with the requirements, b) Tree Replacement Plan - Both the City and District’s certified arborist will inspect the replacement tree planting, and c) Cultural Resources Treatment and Monitoring Plan – The District will furnish an Archaeological monitor and three (3) Native American monitors (from 3 tribes) who will be present for all excavation and an “on-call” Paleontologist.
• Discharge Permit with Santa Ana Regional Water Quality Control Board – The groundwater may be discharged to PCH catch basins located on the west side of the highway. The contractor may not discharge groundwater during periods of exceptionally high tides and storm surges.
• A Notice of Exemption was filed by the District to comply with California Environmental Quality Act (CEQA) requirements.
• A separate Biological Resources Assessment was conducted by the District. A technical memorandum was prepared to show the locations of known sensitive bird nests. The District will furnish a Biologist to conduct a pre-construction meeting and perform required surveys.
• A separate Cultural and Paleontological Resources Treatment and Monitoring Plan was prepared by the District.

Solution

The project goal is to construct approximately 3,300 LF of new 15-inch diameter PVC (polyvinyl chloride) gravity sewer main along a Sunset Beach greenbelt, aka Linear Park, to bypass the pump station at Broadway and divert sewer flows by gravity into the City of Huntington Beach’s sewer system in PCH at Warner Avenue. Construction of the new pipeline involves trenching, with some areas of tunneling. Trench depths will vary between 14 and 16 feet below grade.

To avoid public access impacts no work will occur during the peak use summer months (no work from Memorial Day weekend through Labor Day). In addition, the project is to occur in approximately sixteen phases, with only the length of one phase closed and unavailable to the public at a time. The length of each phase varies, but the phases roughly correspond to one block. The area of one phase will be restored and re-opened to the public before the next phase of work begins.

LEE + RO’s services consisted of preliminary and final design services to prepare final contract documents for bidding and award for construction, including CEQA, permitting, and funding assistance.

Preliminary Design

LEE + RO prepared a preliminary design report that included an analysis of alternative pipeline alignments, materials of construction, and construction methods, etc. The following services were performed during preliminary design:

• Completed aerial topo surveying of the area between N Pacific Ave and S Pacific Avenue for base mapping.
• Reviewed the tie-in invert elevations for the connecting sewer mains to confirm project feasibility.
• Evaluated and verified design flows presented in the feasibility report for pipe sizing.
• Confirmed the 15-inch diameter pipe sizing after calculating the tributary flows based on the buildout of the vacant tributary areas.
• Performed four (4) soil borings including groundwater sampling.
• Reviewed permitting requirements and assisted the District with all necessary permit applications.
• Identified and presented alternative pipeline alignments through available utility corridors.
• Considered and evaluated trenchless construction techniques such as micro- tunneling and jacking & boring.
• Prepared full scale plan and profile drawings for the selected pipeline alignment.
• Prepared environmental compliance support documentation.
• Assisted the District in applying for construction funding.

Final Design

LEE + RO prepared final design plans consisting of general, demolition, civil, electrical, landscape, and traffic control plans. To protect some old, mature trees and to protect nearby City-owned public restrooms, the design consists of a couple of trenchless micro-tunneling or jacking & boring segments. The bid items included optional trenchless segments in lieu of open trench segments, to minimize dewatering.