Wednesday, October 20, 2010

Day 240 October 17, 2010

This is known as the Deep Sinks and the water in this hole is about 20 feet deep. Years ago there were two separate holes but now there seems to be only one. The holes were probably formed by the decomposition of the peat soils, supported by contact with oxygen in the water. Holes like this one are common in older bog wetlands such as the Hylebos Start Park wetland.
The hylebos Wetlans contain peat soils up to 30 feet thick. The peat soils begun to form some 10,000 to 15,000 years ago in a depression left after the last glaciation. The depression held a lake, which gradually filled in with sediment and plant material until it finally became dry enough to support forest growth. Since peat forms in relatively low oxygen conditions the plant materials are only partly decomposed - plant fragments can be seen from plants which died thousands of years ago. Very few examples of this type of wetland remain in the Puget Sound Region, partly because the peat was mined years ago to use as a soil amendment.

The water level in the hole is probably fed by a shallow aquifer (ground water) from Panther Lake area. A deeper aquifer called the Redondo-Milton channel lies underneath this area extending from the Redondo area southward toward Milton. Several wells in the Redondo-Milton channel are the main source of drinking water for Federal Way.

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