San Elijo Joint Powers Authority
Through our current wastewater on-call contract with Portland Bureau of Environmental Services (BES, we have recently worked at CBWTP on projects such as the Digester Gas Conveyance Pipeline Replacement, Effluent Pump Station HVAC Rehab, Organic Waste Receiving Facility, and improvements to existing Digester Domes. KJ has been providing comprehensive on-call wastewater engineering services to BES since 2017.
We have a track record on the current on-call contract of delivering on 4 diverse and challenging engineering task orders:
Effluent Pump Station:
HVAC improvements to the existing electrical room with five 800-HP variable frequency drives (VFDs) in addition to other electrical equipment, with a sixth VFD to be added. The HVAC design was reviewed to address inadvertent system shutdowns due to VFD overheating and over-pressurization of the space when all five effluent pumps were in operation. The electrical room was ventilated by a makeup air unit (MUA) with ducted returns from the VFDs meant to capture heat rejection. These were disconnected due to high static pressure. The electrical room was conditioned via a separate heat pump system which also conditioned the control room.
Organic Waste Receiving Facility (OWRF):
Design and construction services for the installation of a new organic waste (food waste) receiving system. The OWRF will receive macerated slurry from a nearby processing facility, and fats, oils, and grease from contract haulers. The material will be received, stored within new storage tanks, and metered into existing digesters to increase biogas production for beneficial use including renewable energies such as heat, electricity, or vehicle fuel.
Digester Gas Piping:
The Columbia Boulevard Wastewater Treatment Plant has an underground network of steel digester gas piping with sections dating back to the 1970s. Much of the pipe is exposed in a series of tunnels that connect the digesters to the waste gas burner and plant boilers. KJ used the results of infrared thickness testing completed by International Inspection, Inc. to forecast the remaining useful life of the piping. The analysis of over 1,500 feet of pipe resulted in a recommendation to repair or replace more than 400 feet steel piping targeting specific pipe runs based on significant loss of wall thickness to mitigate risk. Pipe replacement was determined by the team to be more constructible than a fiberglass wrap in place, given the difficult access restrictions. This task was complicated by a planned capital project, which would replace some gas piping in less than seven years. Given the anticipated brief service life, KJ proposed standard wall carbon steel pipe versus more durable stainless steel piping in these repair areas to minimize the cost of repairs and promote material compatibility at the welded joints. In addition to the digester gas piping replacement, the sediment tanks and condensate traps located on Digesters 5 through 8 required replacement. Piping had recently been inspected using non-destructive testing to verify wall thickness. Some of the pipe present on the digester roofs was found to be heavily corroded. Our team recommended replacement of the exposed digester gas piping and flexible hose that connected the piping on each digester’s floating cover to the fixed sediment tanks on the adjacent digester building’s roof.
Pipe Condition and Risk Assessment:
The process piping and utility services at the Columbia Blvd. Wastewater Treatment Plant (CBWTP) are critical to the plant’s operation. Many of the plant’s process piping systems are original and have not been recently inspected and are inaccurately characterized in BES’s enterprise asset management system. To reduce the amount of effort required to maintain and rehabilitate these essential plant assets, BES is mapping, inspecting, and developing an asset management system that highlights risk-critical pipe systems and includes over 100 different pipe assets. The pipe assets range in size from 1.5 to 87-inch diameter pipe both above and below ground with varying degrees of access. These pipe systems convey a wide variety of materials including air, steam, biogas, natural gas, solids, non-potable water, plant effluent and more. This project requires extensive coordination between plant operations, inspection firms, design projects and on-going plant construction contractors to map and inspect the pipe systems safely and reliably. With this objective in mind, BES is partnering with Kennedy Jenks to achieve the following key goals to be accomplished utilizing our risk-based approach over the next five years: o Complete inspection of all process piping and utility services within 5 years o Expand the plant’s asset registry by including all pipe types by function, material and remaining useful life o Build a GIS database with individual GIS layers for all process piping that can be linked to inspection reports and other supporting documents o Develop a prioritization decision mechanism process for maintenance, Risk-based Inspections, critical repair and replacement.
