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SHN has over 40 years of experience in environmental services projects, beginning with investigation and remediation of underground storage tanks and mill sites in the 1980s. We have closed investigations on more than 1,000 sites, including state and federal Superfund and Brownfield sites. We enjoy a respectful relationship with regulatory agencies; our fastest project from investigation to closure required just 4 months.
Today, we continue with site assessments, investigations, and remediations and have broadened our environmental services through protection of surface waters, stormwater pollution prevention, landfill monitoring, reclamation of mined lands, and assistance with hazardous materials storage, in Northern California and Southern Oregon. Recently recognized environmental challenges such as sea level rise, urban and wildfire, and climate variability, are beginning to affect sites, primarily by increasing contaminant transport. SHN environmental staff are working to anticipate how these new challenges can be met.
Fernbridge is a registered historical bridge that opened in 1911; it has withstood numerous major floods and earthquakes with varying degrees of damage and subsequent repairs. On December 20, 2022, a magnitude 6.4 earthquake struck 12 miles offshore from the bridge, which caused vertical off-set cracking of bridge piers, particularly in Pier 2. Caltrans and their contractors, including Myers and Sons Construction, began emergency repairs in 2023, with SHN subcontracting to Myers and Sons in January 2023.
Our original scope of work was to sample river water quality weekly, but tasks quickly increased to include nearly round-the-clock sampling and/or observation every 2 hours. Construction impacts, while temporary, had the potential to be significant to the aquatic resources of the Eel River. To access Pier 2, a temporary road was built into the river channel. The pier repair included drilling 6.5-ft diameter boreholes and sinking in circular rebar cages, constructing forms for the concrete, installing sheet piles for controlling water flow, and managing the surface water and dewatering fluid so that it could not drain offsite or into the river.
SHN’s certified Stormwater Pollution Prevention Plan (SWPPP) QSPs (Qualified SWPPP Practitioners) designed construction water and stormwater management mitigations and collected hundreds of surface water samples. Specialized additives were used so that the concrete would set underwater, which complicated sampling because the additives contained high concentrations of chromium, which had to be separated from other potentially affected surface water. Meticulous labelling, handling, and tracking of the many samples was critical because the construction was moving quickly, and there would be no opportunities to “go back” and resample.
SHN collected defensible data for the construction contractor and Caltrans, and performed important work that allowed Fernbridge to reopen for two-way traffic in March 2023, and to have a more permanent repair of Pier 2 by the Fall of 2023.
SHN is continuing to monitor and report to the contractor and Caltrans. Caltrans will install seismic sensors in the vicinity of the bridge and traffic control arms that will close the bridge in the event of another significant earthquake. We are monitoring plant survival and drainage and erosion patterns.
The Tuluwat Village is on an island in Humboldt Bay, is the center of the Wiyot Tribe’s ancestral territory, and is the site of their annual World Renewal Ceremony. Between 1870 and 1990, the site was contaminated with hazardous materials consisting of paints, solvents, metals, petroleum products, and various other chemicals. In 2000, a contractor removed approximately 1,300 pounds of identifiable hazardous wastes from the site, but remaining soil and treated timbers at this culturally sensitive area remained contaminated with PCP (pentachlorophenol) and dioxin/furan compounds. After the timbers were removed, SHN negotiated with the Regional Water Quality Control Board to protect and preserve the cultural aspects of the site while removing a minimal volume of the contaminated soil.
SHN helped the Tribe obtain additional funding for study of in situ chemical oxidation (ISCO), which reduces dioxin/furan compounds and PCP in soils, but does not adversely impact the village’s shell mound and other culturally sensitive materials. SHN also designed and directed repair of the existing bulkhead and installation of a shoreline revetment wall. After the shoreline was fortified, SHN conducted additional ISCO remediation of the residual contamination, and monitored groundwater to evaluate soil remediation success.
SHN won the American Council of Engineering Companies’ 2013 Engineering Excellence Award. This work was further recognized by the US EPA’s Region 9 Excellence in Site Reuse Award in 2018; EPA’s brochure on the project can be downloaded here.
In 2021, SHN continued to assist in recovering this site by writing the overview, detailed scope of work and schedule for Spartina (eelgrass) removal from Tuluwat Island, for the Humboldt Bay Harbor, Recreation and Conservation District. The scope included post-removal monitoring performance criteria and reporting requirements to ensure eelgrass removal success.
An international energy transportation provider owns a property with three landfill cells, which had been used by former and current owners. This project’s goal was to close three landfill cells—Cells 1, 2, and 3—at a coastal bay site. SHN provided a full range of services including civil and environmental engineering, construction observation, materials testing, and regulatory coordination. The project aimed to reduce leachate generation and improve long-term environmental performance through the installation of ClosureTurf® systems and stormwater management infrastructure. SHN’s team led the design and implementation of closure plans, coordinated with the state environmental quality agency, and ensured compliance with all regulatory and engineering standards. We continue to assist in post-closure cost estimates for monitoring and maintenance.
For Cell 3, SHN oversaw the relocation and reshaping of over 30,000 cubic yards of waste, followed by import and compaction of 17,000 cubic yards of sand cover. The team managed the installation of a geomembrane liner and ClosureTurf® system, performed daily construction observation, and conducted compaction and liner seam testing to ensure quality. Challenges included unknown extents of the existing leachate liner, which required field adjustments and redesign of the closure system and stormwater controls. High winds during liner installation were mitigated by adjusting work schedules to early morning hours. Design modifications, such as enlarging anchor trenches and revising stormwater conveyance features, were implemented to enhance durability and reduce maintenance.
For Cells 1 and 2, SHN adapted the original closure design to a top-deck cap system, integrating the two cells into a unified closure area. Services included site grading, installation of ClosureTurf®, and construction of stormwater infrastructure. SHN’s field team provided continuous oversight, ensuring that construction met design specifications and environmental standards. The project required flexibility and problem-solving to address evolving site conditions, including unexpected waste volumes and the need for additional cover material. Through proactive coordination with the state environmental quality agency and the client, SHN successfully delivered a robust and environmentally sound closure solution that supports long-term site stability and regulatory compliance.
The SHN environmental services team fast-tracked environmental assessments for a private petroleum distributor in southern Oregon. SHN’s scope of work included preparing Phase I Environmental Site Assessments (ESAs) and Phase II ESAs across 15 sites. All sites were visited and 14 of the 15 sites were sampled via Geoprobe® for soil and groundwater, if present, to document the current subsurface conditions. Samples were screened in the field with a photoionization detector, and those with elevated levels were sent to a laboratory for chemical analysis.
This project was notable for 1) the extensive collaboration required, involving three SHN offices and our entire environmental services team, and 2) the accelerated timeline of 65 days from kick off to deliverables. The project faced several technical challenges, such as short-notice subsurface utility surveys, permitting issues, coordination with multiple subcontractors, short sample holding times, and adverse winter weather conditions. Despite these challenges, SHN successfully provided the client with detailed reports on the historical uses of each site and the subsurface conditions of 14 fueling stations and one oil product storage property, demonstrating our experience in managing complex environmental assessments under tight deadlines.
Location: 15 sites throughout southern Oregon
Owner/Client: Hays Oil Company
Partners: NA
Project Timeline: 65 days from project kick-off to deliverables, 2024