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In the late afternoon on April 6, Subaru Telescope staff discovered a glycol leak from a mirror handler maintenance cart. The spill was fully contained within the telescope’s facility, and following a thorough investigation, no threat to Maunakea’s environment was found.

The cart, which was last used for the telescope’s primary mirror re-coating in July 2022, was stored on the first floor of the Subaru Telescope dome. Approximately 0.2 pounds (0.09 liters) of glycol spilled onto the floor and some glycol dripped from a filter cartridge onto the cart. To prevent further spread of glycol, the spill was immediately cleaned up and the cart was wrapped with spill-kit sheets and socks. The following day, Subaru Telescope staff conducted a thorough inspection of the entirety of the leakage spot and found up to four pounds (approximately five liters as 40 % glycol water) of glycol may have spilled and lost over the previous eight months. It was last documented that the cart’s reservoir tank held 15 liters of glycol. As a permanent preventive measure, Subaru Telescope staff fully emptied the reservoir tank and replaced the filter cartridge.

Since it was possible that glycol could have spilled from the floor into a gap in the dome’s slab, Subaru Telescope staff conducted a thorough examination of the surrounding area with an endoscope. Although we observed several droplets of glycol on the side wall of the slab, no glycol was observed to have reached the bottom of the slab. We believe there is no contamination to the soil or environment since no contamination was observed on the two-inch sand layer and vapor barrier layer under the slab.

We understand that it is a privilege to conduct astronomy on Maunakea and are committed to taking steps to prevent incidents in the future.

Notifications were made to our resource management and regulatory bodies, the Center for Maunakea Stewardship (CMS), The University of Hawai`i-Hilo and the Hawai`i State Department of Health.

We will continue to operate Subaru Telescope with the utmost care so as not to cause environmental pollution, and if by any chance a problem does occur, we will respond promptly to minimize the impact.