Sinkhole Repairs
Understanding Stormwater Sinkholes
Sinkhole is a term used to describe a depression or open cavity in the earth’s surface. Often, they begin as a dip or depression in a parking lot or grassed area. Overtime, especially when exposed to rain, the subgrade soils erode, leaving a large cavity that continues to grow.
Why do Sinkholes Appear?
Sinkholes can be a sign of premature infrastructure failure. Sinkholes may occur around a structure like a catch basin or outlet control structure. These sinkholes are often due to joint separation where the connection between structures or pipes weakens and allows water and subgrade to enter through a fracture.
A weak point in water infrastructure will always compound into a larger issue because constant infiltration during rain events adds strain to the structure and compounds the issue. The issue may be related to joint separation, improper connection, cracks or root infiltration. To properly understand the issue with your property, it is essential to first inspect the infrastructure, often done with a remote-controlled camera (CCTV).
The high velocity of the running water exploits openings or deficiencies in structures. What starts as a small failure will grow as it is continually exposed to stormwater. Eventually it will allow water to escape the pipe. As water exits the pipe, it loosens the surrounding soil, causing the soil to wash downstream. Once the soil is loosened by the stormwater, it is no longer compacted and disrupts what was a delicate balance. In many cases, the stormwater outside of the pipe continues downstream loosening the compacted soil and creating more displacement. As the soil is displaced, the ground above settles into the empty space creating a depression on the surface. Eventually, this depression opens revealing the cavity below.
Watch our Webinar on Stormwater Failure
Sinkholes Stabilization
Sinkholes will continue to expand as more rushing water displaces additional soil within the subgrade. It is crucial to consult a stormwater professional as sinkholes are extremely dangerous. What is visible from the opening of the sinkhole may only be a small portion of the cavern below. It is important for professionals to identity the root cause of the sinkhole, through various means including but not limited to CCTV, exploratory digs, geotechnical surveys, etc. To stabilize the sinkhole, professionals must first divert any water away from the area. The root cause must be corrected to restore the system and prevent additional loss of subgrade soils. Then loose soils can be removed and replaced with appropriate fill material for the severity of the opening.
Common Places for Sinkholes
- Catch Basins
- Outlet Control Structures
- Headwalls and Endwalls
- Junction Boxes
- Retaining Walls
- Above Pipelines
Sinkhole Leads to Stormwater System Rehabilitation
What originally started as a small depression in the area surrounding this commercial office space, was a symptom of severe system failure underneath. Read more about the diagnosis of the stormwater failure and the rehabilitation that followed.
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