Over the past 2 months, precipitation has been way above average (14.89”); which has resulted in a few flooding events. When the rain comes down in that amount, in that short of time, you are bound to experience bunker washouts (seen below).
Washouts occur when the rain either comes down at a high rate, or a steady stream of surface water drains into the bunker, causing the sand to fall towards the middle of the bunker and exposing the clay bases. Every time the washouts happen and expose the clay bottoms, the washed sand will mix with the clay base, causing contamination.
The darker sand is contaminated, meaning it is mixed with some clay. The contamination resulted from surface drainage from the fairway flowing into the bunker.
Over time, many storms alike will affect the performance of the sand (i.e hard bottoms, layering, poor drainage (seen below), etc).
The common misconception amongst golfers is when we receive frequent heavy rains, that the contaminated bunkers have no sand. The playability may seem to indicate there is no sand, but in actuality, the bunkers all have plenty of sand. (See below.)
Left-side pic: The dark spot is a wedge shot bouncing off a contaminated layer
Right-side pic: Sand dug in that same spot with 6” of sand underneath
The long-term corrective mode of action is to remove the contaminated sand and replace with new sand. In fact, according to the American Society of Golf Course Architects, bunker sand should be replaced every 5-7 years, depending on location, design, weather, and care. The last time GBCC’s green-side bunker sand was replaced was 2012 and fairway sand 1995.
The Grounds crew have identified a handful of bunkers with the contamination issues and will perform the proper care in Spring of 2019.