STEVE P. RADOS, INC

Constructs New Generator Building While Performing Major Upgrades on the Pump Station 2 Power Reliability and Surge Protection Project in San Diego

By Ian Hoover, Editor

San Diego Public Utilities Department maintains a Capital Improvement Program (CIP) that supports the infrastructure for reliable water supply and wastewater collection and treatment within the San Diego region. The Department’s system supports 1.4 million water and 2.5 million wastewater customers within their district. The water system provides approximately 171 million gallons per day (mgd) within a 4,040 square mile radius.

The Municipal wastewater system, in particular, consists of roughly 3,000 miles of pipelines and 77 sewer pump stations used to convey wastewater from residences and businesses in the City of San Diego. There is also the Metro System, which consists of three wastewater treatment plants, one biosolids processing facility, four large pump stations, and two outfalls. Metro provides treatment and disposal services for the City and 12 other agencies and districts within a 450-mile area.

Pump Station No. 2 (PS2) is the City’s largest sewage pump station and was placed into operation in 1963. PS2 receives wastewater flows from North Metro Interceptor (serving the North San Diego region), and the South Metro Interceptor (serving the southern communities of San Diego). The entire wastewater flow from the Metropolitan Wastewater System is collected at PS2 and conveyed by two 87-inch diameter force mains, to the Point Loma Wastewater Treatment Plant. PS2 has been the subject of numerous improvement projects over the years. Because PS2 has not met all of the requirements of the EPA Class 1 Reliability and force main surge protection standards, it was determined that it should undergo additional construction to bring it into compliance.

This approximately $56-Million improvement project was awarded to Steve P. Rados, Inc., in July 2017 as the general contractor. The EPA recommends that facilities like PS2 be equipped with two separate and independent sources of electrical power. This should be provided by either two separate utility substations from a single substation equipped with plant base generators. The current contract calls for the installation of two 3,000 kW natural gas engine-driven generators, and two 4,000 kW diesel engine emergency generators to meet peak sewage demands should direct utility feeds be interrupted. The job also requires the replacement of two engine drives with 2,250 HP electrical motors and variable frequency drive pumps (VFDs). Steve P. Rados, Inc. is also constructing an 8,000 sq. ft. new concrete building to house the generators, cooling systems, electrical switchgear and cranes. Other construction items include upgrading the heat exchange system, the installation of new fuel storage tanks, a new refueling system, piping, instrumentation, office improvements, handicap facilities, restroom improvements, new office space, and conference rooms, along with several other tenant improvements.

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Moving 2,500 HP motors into the existing operations building.

Site utility excavation and installation.

Temporary safety rail installation for protection during proposed concrete deck placement.

Dennis Jaich is the project manager overseeing the PS2 Power Reliability and Surge Protection Project for Steve P. Rados, Inc. (Rados). “This project will improve pumping capacity and power reliability, with standby power at the pump station that will protect against surges during outages, ultimately preventing sewage spills,” says Jaich. “Because nearly 80 percent of the City’s sewage flows into PS2 and ultimately on over to Point Loma, it is critical that PS2 remain operational during emergencies.” According to Jaich, Rados began their work on PS2 in August 2017 and is expected to have everything wrapped up by November 2022. “We began construction on the new generator building performing soil improvements by injecting Compaction Grout, an application of lean concrete into the existing ground. This process involved injecting approximately 500 cubic yards of grout to depths of 40 to 50’ (at 5’ on center) below our projected excavation. This process was required to stabilize the existing ground which showed signs of having significant compaction deficiencies which may not allow the weight of the new building to be supported properly” says Jaich. “We followed this process by excavating down approximately 12 feet, followed by another round of compaction which then allowed us to stabilize the ground and begin with forming and pouring of the footings.”

Jaich explains that all of this was being done while crews began forming and pouring three separate sections of vertical generator building walls. An enormous amount of rebar of various sizes and around 6,000 cubic yards of concrete has gone into the building process. “The first section is what we refer to as the stem walls, and this was poured to around 10 feet in height. These were compartmentalized into rooms and presented a challenge in the fact that they were not all simple, straight lines, but included several angles and separate concrete trenches,” continues Jaich. “After this section was poured and cured, we began construction of the second lift. This section was around 25 feet in height and was constructed with red architectural concrete that included a horizontal reveal that resembled the appearance of lumber.”

Jaich says that the final wall section or lift was done in stark white coloring and included concrete indentations to represent local topography. The form liners used for the concrete casts were hand-sculpted. “This section extended the building another 20 feet in height and required the use of scaffolding and fall protection devices. Although our production was slowed when working at this height, we maintained safety as our main focus and concern,” continues Jaich. “After completing this final wall section, we moved on to installing the roof with structural steel beams. We are currently placing a steel deck on top of these beams, and then we will place a concrete roof, with specialty air conditioning units and other equipment sitting on top of it.”

The architectural building shell completed, showing the reveal and form liner placements.

Steve P. Rados, Inc. has more than two years left on this project. After the new building is complete, they will move on to the installation and construction of line items that are not quite as visible, but just as challenging. This includes extensive modifications to SDG&E’s power feed and 4.16 kV distribution systems. Also, the generators and pump sequencing controls will be configured to prevent surge and meet the Class 1 reliability criteria. “We are performing all of our work on around a 1/3 acre lot. Access is minimal, as we also face the challenge of storing materials,” says Jaich. “Beyond that, we also have the challenge of working on and around an active critical pump station. All of the existing equipment must be kept safe and functioning at all times. We have also been working through most of the wet weather due to our tight schedule. Our crews have done a great job of successfully diverting

Steve P. Rados, Inc. has nearly 100 years of heavy engineering and construction experience, with a proven track record of outstanding performance on diverse projects. Their work ranges from bridges and interchanges to water transmission lines, sewer systems and treatment plants, along with a variety of other heavy infrastructure type projects. For more information on Steve P. Rados, Inc., please visit www.radoscompanies.com or call their Santa Ana headquarters at (714) 835-4612. Cc