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Collar Dams: An Aeration Side Effect, USGA East Region Update

Brian Gietka | Published on 9/11/2023
Brian Gietka, agronomist, East Region

Collar dams are a common sight on putting greens and cause a number of turf health and playability issues.

It’s the time of year when days are getting shorter, temperatures moderate and we shift from playing defense to improving turf health. Late summer and fall are traditional aeration times for many golf courses in the Northeast. The benefits of this practice are well known, but a common negative side effect of aeration and topdressing is collar dams. During the process of sweeping and blowing sand topdressing into aeration holes, it tends to accumulate along the putting green edges and collars. As sand builds up over time, the collars elevate.

When the sand buildup in collars exceeds the elevation of the putting surface, problems arise. Golf balls can settle along the collar like a pool table rail, which affects playability. Another issue is the raised collar acts like a dam, slowing or impeding surface drainage from the putting green. If you are seeing weak turf and/or many ball marks along the front or edges of a putting green, inspect the collar elevations. Collar dams will make adjacent areas softer, which leads to more ball marks and spike marks. In severe cases, collar dams can create chronically wet areas that are prone to poor turf health, pest problems, mechanical damage or winter injury. 

To remedy collar dams, core aerate, remove the plugs and repeat. Then water lightly and use a vibratory plate tamper to lower the dam. If the turf is weak, lay a sheet of thin plywood down and vibratory tamp on top of it to protect the turf. Allow the turf to recover and repeat as necessary until water freely runs off the putting surface. Additional aerator passes and tamping may be needed into the approach or rough to ensure effective drainage. In severe cases, you may need to strip elevated areas, remove enough soil to eliminate the dam, and then replace the sod. If you have bermudagrass, a fraise mower works well to lower collar elevations with the added benefit of removing weed seeds in the soil. 

Pay attention to removing and dispersing sand buildup along putting green edges during aeration before it becomes a problem. Taking the time to eliminate existing collar dams will improve playability and gives a firmer, healthier putting surface. 

Northeast Region Agronomists

Darin Bevard, senior director, Championship Agronomy –

Elliott L. Dowling, regional director, East Region –

Brian Gietka, agronomist –

Information on the USGA’s Course Consulting Service


(616) 834-0450