2013 Water System Plan, Volume II - Seattle City Clerk's Office - City ...

Groundwater Elevations at Seattle Well Fields
November 2011
SPU monitors groundwater levels in the vicinity of the Riverton and Boulevard Park Well Fields
as part of its management of this supply source. Underlying the area are three water-bearing,
sand and gravel formations now known as the Shallow, Intermediate and Deep Aquifers. The
aquifers are arranged in layers and separated by much less pervious silt and clay layers which act
as aquitards. At the land surface, over much of the area, is a highly compacted layer composed
of glacial till. SPU has three production wells tapped into the Intermediate Aquifer.
In addition to the production wells, SPU has a network of six monitoring wells in the Well
Fields. Three of these wells can monitor water levels in the intermediate aquifer, two in the
shallow aquifer, and one in the deep aquifer. Data loggers collected continuous elevation data
from the monitoring wells from late 1991 through late 1999, primarily during and immediately
after the ASR demonstration project. Routine collection of water level data from the observation
wells was suspended in early 2000. In the absence of recharge operations, it was felt that levels
recorded continuously in the three production wells by the SCADA system would adequately
track trends in the intermediate aquifer. Data are available from this system starting in January
2003 and from SPU’s I-SCADA IMS Data Portal starting in April 2005.
The graph below shows the groundwater elevations from the SCADA system at the Riverton and
Boulevard Park productions wells from January 2006 through December 2010. Also shown in
the graph is total daily production from the three wells. No long-term trends appear in the data.
Short-term declines occurred in May and June 2008 when the wells were used for 24 days, but
levels quickly recovered when pumping ceased.
SPU will continue to monitor the elevations in the production wells for any trends, and will reactivate
the monitoring well network if recharge operations are undertaken.
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