Historical Research & Investigation of Sinkhole Formation

Project: Investigating the Formation of a Sinkhole on a Residential Property

Introduction

This case study details the investigation into a large sinkhole that formed in the front yard of a residence. The investigation aimed to determine the cause of the sinkhole (natural or man-made) and to ascertain if there was a history of sinkholes in the Subdivision, a concern raised by the homeowner.

Project Background

Homeowner purchased their home in 2021. In August 2024, a significant sinkhole, approximately 10 feet in diameter and 19-20 feet deep, suddenly appeared in their front yard, adjacent to the driveway. The homeowner filed a complaint with the builder, alleging that the company failed to disclose the history of sinkholes in the subdivision prior to her purchase.

Although there was no apparent structural damage to the residence, the County Fire Department advised homeowner not to use their asphalt driveway within 10 feet horizontally of the sinkhole.

The builder, through their Regional Construction Manager, requested PWR Engineering to conduct an in-depth investigation into the sinkhole's formation and the historical context of sinkholes in the Development.

Sinkhole Investigation

The investigation focused on two primary areas: determining the origin of the sinkhole and researching the historical presence of sinkholes in the subdivision.

1. Origin of the Sinkhole

• Mining Activity Check: A phone call was made to a limestone quarry and cement manufacturer located adjacent to the property. They confirmed that no mining activities had occurred near homeowner’s residence or within 500 feet of the property.
• Environmental Data Research (EDR) Report: An EDR report was commissioned to research all environmental activities within a quarter-mile radius of the homeowner’s property. This report included topographic and aerial map records of governmental mapping.

2. Historical Sinkhole Research

• The EDR report's mapping history was analyzed for documented occurrences of sinkholes or man-made activities.
• Additional photo records were reviewed to identify any past sinkhole formations in the vicinity.
• Builder’s due diligence records regarding environmental assessment studies conducted prior to the development of the subdivision (construction began in 2019 and concluded in 2023) were considered.

The Findings

The investigation yielded the following key findings.

Sinkhole Origin

The EDR report's mapping history indicated that the sinkhole occurrence at homeowner’s is natural. There were no man-made activities or historical documentation of sinkholes at this specific location within the Subdivision. Limestone quarry and cement manufacturer nearby also confirmed no mining activities in the immediate vicinity.

Nature of Sinkholes

Sinkholes are natural depressions formed by karst processes, involving the chemical dissolution of carbonate rocks (like limestone) by percolating groundwater. They are common in areas with soluble bedrock and can form gradually or suddenly.

The documented sinkhole is consistent with natural geological processes and is not a result of human activity or construction by Builder.

Historical Context

While no history of sinkholes was documented specifically within the Subdivision during its development (2019-2023), photo records revealed that a very large sinkhole did develop in 2016 within 500 feet of the homeowner’s property. This historical sinkhole was fully backfilled by the cement plant and is currently stable.

Builder’s due diligence prior to developing the subdivision did not report any evidence of previously occurring or evident sinkholes within the pre-developed land.

Conclusion

Based on historical research and investigation, sinkhole formation is determined to be a natural geological occurrence. There is no evidence to suggest it was caused by man-made activities or construction. While a large sinkhole did occur within 500 feet of the property in 2016 (which was remediated), there was no historical evidence of sinkholes forming within the Subdivision itself prior to or during its development that would have been disclosed by Builder through standard due diligence.