Spurr-Crater Peak: 1953 & 1992

Spurr erupted in 1953 and 1992 in Alaska, U.S.A.

Water Supply

Anchorage is the largest city in Alaska, located 120 kilometers east of Mount Spurr. The 1953 eruption of Mount Spur deposited 3-6 milimeters of ash on the city, causing short term pH and turbidity problems with the city's water supply (Wilcox, 1959). The pH level fell to 4.5 before returning to normal after a few hours. Turbidity rose from 5 ppm to 290 ppm and lasted six days before returning to normal.

The August 1992 eruption deposited about 3 milimeters of fine sand-sized volcanic ash on the city (Johnston, 1997b). The clean-up of ash resulted in excessive demands for water and caused major problems for the Anchorage Water and Wastewater Utility (AWWU) water production and distribution systems (AWWU pers comm.). The AWWU received a warning of the impending ashfall on the afternoon of 18 August. No action was taken that evening.

As one staff member described "we did not equate ashfall to high water demand... we were not prepared for what happened... had we known we would have moved to fill reservoirs sooner." By 10 am on 19 August (the day following the ashfall) a peak four hour demand of 230 million litres per day was recorded, about a 70 percent increase in normal demand. Despite adequate production capacity, physical restrictions within the distribution system prevented the utility from moving sufficient water volumes to meet demand in parts of Anchorage.

The high water demand caused widespread water-pressure and -supply problems throughout 19 August, with levels in several storage reservoirs dropping to dangerously low levels. Some reservoirs were isolated from the immediate distribution system to ensure adequate volumes for fire suppression if required. At least one reservoir was completely emptied. Had fires occurred in parts of the city no water would have been available.

Opening of the Anchorage International Airport was delayed for several hours due to a shortage of water with which to clean the runways. Stranded passengers were unable to use the toilets due to the lack of water.


The city of Anchorage was covered by 3 milimeters of volcanic ash from the August 1992 eruption of Mt. Spurr volcano, located 125 kilometers to the west. Although care was taken to minimize the amount of ash entering the stormwater system, large amounts of ash still had to be removed the following spring. Ash did not move far into the system but settled out rapidly, eventually forming a hardened deposit. During the spring thaw some local flooding occurred due to pipe blockages. The ash was removed from the pipes using vacuum trucks.