Road Services - Pothole repair
How to report potholes or roadway defects
Roads Services provides customer service, 24-hours a day, seven days a week for reporting any potential problems or concerns affecting the roadways throughout unincorporated King County. To report a pothole or roadway defect call 206-296-8100 or 1-800-KCROADS.
To ensure that the repairs you are requesting are handled in a timely and efficient manner, please have the following information available at the time of your call:
- Your name.
- Your address and daytime phone number. (It is important that you provide a contact number in the event more information is needed.)
- The location of the pothole, including the nearest cross street and/or address.
- A description of the problem. (There are other types of road defects that may appear as a pothole, but may require more intensive repairs.)
- Any other pertinent information that may need to be relayed to the crews about the area or the problem.
How potholes form
There are several different ways that potholes form, but the most common cause of potholes in the greater King County area is due to moisture seeping into small cracks in the pavement. Moisture, most often rainwater, sinks through small cracks in old or weakened asphalt. The water is then soaked up by the mixture of rock, gravel and sand that supports the roadway. This is why potholes can appear to develop overnight and after periods of heavy rain. Overtime, vehicles passing over the road force water deeper through the soggy roadbed, eventually eroding parts of it. As the roadbed continues to erode the asphalt begins to sink into the eroded portions and eventually cracks under the continued impact of vehicle tires. Other contributing factors in the creation of potholes are high traffic volumes, roadbed base failure, drainage problems near or under the roadway, petroleum products, such as diesel or gasoline spilling on the asphalt, frost boils, and utility failures.
Diagram of pothole formation
|RAINWATER SINKS THROUGH CRACKS IN OLD OR WEAKENED ASPHALT. THE WATER IS SOAKED UP BY THE MIXTURE OF ROCK, GRAVEL, AND SAND THAT SUPPORTS THE ROAD.
||VEHICLES PASSING OVER THE ROAD FORCE WATER THROUGH THE SOGGY ROADBED. EVENTUALLY ERODING PARTS OF IT.
||ASPHALT SINKS INTO THE ERODED PORTIONS OF THE ROADBED AND EVENTUALLY CRACKS UNDER THE CONTINUED IMPACT OF VEHICLE TIRES, CHUNKS COME LOOSE.
||HOLES MAY BE PATCHED WITH PROPRIETARY COLD PATCH OR HOT PATCH MATERIAL
Once Road Services staff are notified of a pothole, a crew is dispatched to repair the defect. King County primarily uses an asphalt emulsion cold mix or the square cut patch method to repair potholes, depending on the size and condition of the roadway. For small to medium sized potholes, crews fill the void with water based mixing grade asphalt emulsion. This method is both environmentally and economically friendly and effective in repairing these types of roadway defects. For larger sized potholes, square cut patching may be required to effectively correct the problem. This requires grinding or cutting out a portion of the roadway surrounding the pothole, repairing the sub-base material and patching the roadway surface. A less commonly used method of pothole repair includes the use of asphalt concrete.
Other types of roadway defects
While most people refer to roadway defects as potholes, there are various types of roadway defects that are caused by different factors and may require different methods of repair. Some of these defects include:
- Sinkholes which are deep or large voids underneath the roadway surface
- Raised, sunken or missing manhole covers
- Bumps that result from the roadway being pushed upwards
- Ponding caused by low points in the roadway, inadequate drainage systems or improper grading
- Raised, sunken or missing utility hardware or old utility cuts
These types of defects may require a longer investigative and/or repair time than a pothole.
Visit our glossary for an explanation of common road terms and jargon.
Road Services Division
Traffic and Road Maintenance Section
155 Monroe Ave. N.E.
Renton, WA 98056
Also see: Additional contact information
Information from the Road Services Division's website is available to people with disabilities in alternate formats upon request by calling 206-477-3839 or 711 for the TTY relay service.
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