Getting Geotechnical: ASTM International Publishes First-Ever Preliminary Karst Assessment Standard Practice

Multiple factors paved the way for the first-ever standard practice produced by ASTM International for preliminary karst assessments, including:

• Alarming stories about sinkholes widely followed by consumers.

• An emerging hodgepodge of karst assessment requirements as local development boards tried to respond to public interest.

• Increasing demand for liability protection.

ASTM International’s D8512-23 “Standard Practice for Preliminary Karst Assessments for Site Development” was published in December 2023. Karst, characterized by the presence of sinkholes, caves, sinking streams and areas of soil subsidence, is found in about 30 percent of the U.S. geographical area.

Why Now

Particularly since the early 2000s, a growing number of news reports about sinkhole events began to alarm the public. Two such events stand out: a 2013 sinkhole that opened under a Florida man’s bedroom, taking him with it; and a 2014 sinkhole that swallowed rare and expensive Corvettes at the National Corvette Museum in Kentucky.

Assessments for the potential of karst impacts soon became a requirement for development project permitting and approval. Planning boards and zoning commissions wanted them as a response to community concern. Project participants, principally financing and insuring parties, wanted them for liability protection. Development advocates wanted them as an objective tool to respond to the NIMBY (not in my backyard) contingent that would point to karst risks, present or not, as a reason to halt a development project.

The problem with such karst assessments was the lack of uniformity and coherence from jurisdiction to jurisdiction, including the qualifications of the investigator, the assessment scope, ranking of karst terrains, the terminology, reporting and recommendations, and more.

How the Standard Developed

At the urging of the ASTM International Soil and Rock committee (D18) and building on work completed by others (particularly that of the Virginia Cave Board, an advisory board to the Virginia governor and legislature on cave and karst issues), an ASTM karst subcommittee was approved and began working on a standard practice for preliminary karst assessments in February 2020.

It took three years to develop, and the standard practice draft went through three subsequent rounds of reviews and balloting. After it went through the subcommittee, all 700 members of ASTM’s Soil and Rock committee had their say as well. Any objections required a response as well as corrections and/or edits as needed. All committee members had a vote, and it finally passed in October 2023.

A Standard Written in Plain Language

Although nine pages long, the standard practice for preliminary karst assessments for site development is presented in language so non-technical stakeholders can understand it. Further, assuming the assessment is carried out and reported as described in the standard, stakeholders can understand the findings to make informed decisions regarding karst risk.

Select elements of the standard practice include the following:

1. The Qualified Professional

The description of the “qualified professionals” necessary to carry out the standard is defined as “individuals (such as engineers, soil scientists, geophysicists, geologists, etc.) who have the appropriate experience and, if required by local regulations, applicable certification, licensure or registration.”

 

2. The Procedures

Generally, procedures of the assessment fall into two main categories:

• A desktop review of available information such as found with digital elevation models (DEMs), Light Detection and Ranging (LiDAR), satellite imagery, topographic maps, aerial photographs and karst condition reports.

• A field survey guided by a site reconnaissance plan based on the results of the desktop review.

3. Findings and Reporting

As written in the standard practice, since the site is in mapped or identified karst terrain, final ranking of a site will fit in one of the following categories:

• There’s minimal karst influence (except subsurface influence) on site use and development. While the site should be considered as having minimal potential for karst development, a karst remediation and management plan should be developed prior to the start of any onsite construction activities.

• It’s likely that karst will influence or there’s future potential that karst will influence site development. Like the first ranking, a karst remediation and management plan should be developed prior to the start of any onsite construction activities.

• Karst will play a significant role in future planning and development at the site. In the case where there’s potential for adverse impact to the proposed development, a detailed site investigation may be required. Based on the investigation’s results, a follow-up report should be prepared, summarizing findings and assessment relative to the proposed construction or development. Per the standard: a karst remediation and management plan shall be developed prior to the start of any onsite construction activities.

A Standard Practice That Informs Project Cost, Timeline and Liability

Prior to the publication of this ASTM International standard practice, karst conditions often were found after site construction activities were underway, with the results of follow-on technical investigations often incomprehensible to those without geological training. In the meanwhile, project timelines, costs and liabilities would grow.

Alternately, inexperienced providers would conduct cursory karst reviews that could lead to incorrect assessments of a site’s karst risks, making the project subject to all manner of dire consequences such as financial loss, negative environmental impacts and threats to human health.

Depending on where it is in the United States, a development site can have a high likelihood of having karst considerations. ASTM International’s standard practice for preliminary karst terrain assessment for site development, if performed and reported according to this protocol, gives stakeholders the essential starting points for an evaluation that facilitates informed decision making regarding a site’s relative karst risk, need for further study and/or potential corrective actions.