Hamilton Street Bridge Site

We held a public comment period September 28 - October 27, 2020, for a Cleanup Action Plan (CAP) amendment, Prospective Purchaser Consent Decree, and Scope of Work and Schedule for a multi-family residential development Sagamore Spokane, LLC is building on a portion of the site.

The CAP amendment explains how the development will enhance the cleanup actions already in place, prevent contaminants from leaving the site during construction, and protect occupants of the new buildings. The Scope of Work and Schedule details engineering, construction, and operations and monitoring reporting requirements, and the schedule for completing these milestones.

Ecology held a public meeting October 14, 2020, (view the presentation), and we responded to two sets of comments. The draft documents were finalized with minor modifications to the CAP amendment to ensure new pilings don't adversely affect groundwater.

The site is along the Spokane River under the Hamilton Street James E. Keefe Bridge. The site is made up of two adjacent properties, which housed the Spokane Manufactured Gas Plant and American Tar Company. We combined these two properties impacted by the business operations into the Hamilton Street Bridge site.

The Spokane Manufactured Gas Plant produced coal gas and carbureted water gas between approximately 1905 and 1948. The facility was used for mixing, storing, and distributing a propane-air system from 1948 to about 1956. In 1956, the company changed its name to Spokane Natural Gas Company and distributed natural gas from the facility. In 1958, Washington Water Power Company, now Avista Corporation, merged with the Spokane Natural Gas Company. Natural gas continued to be dispensed from the site until about 1963 when Richard Brown leased the property. In 1978, he purchased it, and in 1982 it was deeded to Spokane River Properties, of which he is a general partner.

The parties responsible for cleanup are Avista Corporation, BNSF Railway Company (BNSF), and Spokane River Properties, Limited.

Contaminants in soil included volatile organic compounds (VOCs) and semivolatile organic compounds (sVOCs), polycyclic aromatic hydrocarbons (PAHs), and metals.

Groundwater samples taken from points surrounding the soil-contaminated area detected relatively few of these materials. Contaminants that were found leaching into the groundwater are undergoing biodegradation and attenuation through physical, chemical, and biological processes. 

Investigations show that the Spokane River is not being adversely impacted by the site.

From 1997 to 2006, the parties responsible for cleanup completed several cleanup actions. A compacted gravel surface serves as a cap that blocks human exposure pathways (ingestion, contact) to contaminated soil.

A restrictive covenant prohibits activities that might result in the release of contaminants. It also ensures the gravel cap and the two building foundations that remain as caps over contamination will be maintained and undisturbed.

Periodic reviews

When restrictive covenants are used, Ecology reviews site information about every five years. We have completed three periodic reviews for this site.

From 2022–2023, we reviewed groundwater monitoring data from 2015–2022 visited the site July 13, 2022, and published the third periodic review. We found Sagamore's construction site fenced and secured. They are following the terms of the Cleanup Action Plan Amendment to prevent exposure to contaminated soil while building the multi-family housing development. We generally found that the cleanup remains effective, but there was evidence of trespassing and people camping along the river. Trees along the riverbank, which were part of the cleanup remedy, had been cut for firewood. We responded to comments from Avista, LimnoTech, and Landau Associates.

Ecology recommended that Sagamore and the parties responsible for cleanup work together to prevent illegal camping and riverbank access and destruction. We added some new groundwater monitoring requirements. When Sagamore's construction is complete, the Operations and Maintenance Manual for protecting the cleanup will be updated to clearly define responsibilities for Sagamore and the parties responsible.

In 2015, Ecology completed the second periodic review and found the cleanup protective of people and the environment. Soil cleanup levels had not been met; however, the cleanup complied with standards, since the cap was in good condition.

Total arsenic and dissolved arsenic were reported above standards during the March 2015 groundwater sampling. Other sampling events around this time showed concentrations of arsenic, mercury, cyanide, and PAHs above standards. We recommended that changes in contaminant levels above state standards, particularly in wells next to the Spokane River, be evaluated to determine if they are impacting the Spokane River.

In 2010, Ecology completed the first periodic review and found the cleanup was still protective of people and the environment. The cap appeared in good condition, with no signs of excavation or other disturbance. No repair, maintenance, or further actions were required.