D18.27 - Karst

SIGNIFICANCE AND USE
5.1 This practice may serve to assist qualified professionals in conducting preliminary karst assessments, and helping design professionals, plan reviewers, public works officials, and jurisdictional regulators in determining the minimum elements that should be expected in a site evaluation. It should be emphasized that the protocol presented herein is not intended to serve as a substitute for detailed subsurface investigations, or to supersede any existing karst regulations or codified protocols.  
5.2 According to Gutiérrez et al. (3) it is important to understand that geo-hazards in karst terrain differ considerably from other natural settings. These geo-hazards are exacerbated by the redirection and concentration of water draining into the subsurface and removal of soil or other natural cover over karst openings. The karst system is often unable to manage the effects of heavy rainfall and flash floods, resulting in the formation and/or reactivation of sinkholes, soil subsidence or slope movement, and these effects become exaggerated by human alteration of the natural drainage. In addition, the lack of filtration inherent to karst hydrogeologic systems can result in transport and migration of a diverse variety of water-borne contaminants, including but not limited to pathogens, heavy metals, sediments, free-product, and dissolved-phase chemicals, as well as residual-phase contaminants adsorbed on sediment. The removal of cover by grading will reduce support over cavities in the subsurface and increase the potential for collapse or subsidence, particularly where surface water concentration occurs.
SCOPE
1.1 This practice defines and summarizes various procedures for assessing specific sites for potential adverse impacts that karst conditions might have on site development including proposed construction or site management and impacts to the resource. Resources impacted may include water quality, water supply, cave, or aquifer fauna, and/or cultural or scientific resources. Karst impacts to site development include collapse and subsidence, differential subgrade conditions (for example, shallow bedrock, voids, soft soils, etc.), non-uniform bearing, excavation difficulty, and dewatering. The goal is to identify the relevant conditions for consideration in site selection and design. It is intended to offer various courses of actions that will provide a rational framework for planning and implementing a site characterization program to define potential karst conditions that might impact or be impacted by site development consideration for site suitability assessment. It is of note that the site assessment can use any combination of the included procedures  
1.2 Since the site is in mapped or identified karst terrain, final ranking of a site will fit in one of the following categories:
(1) There could be minimal karst influence (except subsurface influence) on site use and development;
(2) It is likely that karst will influence or there is future potential that karst will influence site development;
(3) Karst will play a significant role on future planning and development at the site.  
1.3 Objectives guiding the development of this practice are:
(1) to synthesize and put in writing customary practice for preliminary karst assessments,
(2) to facilitate high quality, standardized preliminary karst assessments, and  
(3) to clarify an industry standard practice for preliminary karst assessments to provide a protocol for these assessments to assist design professionals, plan reviewers, public works officials, and jurisdictional regulators in making an informed judgment on site development and management.  
1.4 The use of this practice is limited to the scope as set forth in this section. However, the report might be of interest and useful in endeavors that the site characterization and report do not address. It is beyond the scope of this practice to include recommendations to any ...