National survey of engineering geology map symbology and data repositories

In support of the US GeoFramework Initiative, the Illinois State Geological Survey has been tasked by the United States Geological Survey to (a) characterize existing standards and guidelines used by individual states related to the visualization and dissemination of engineering geology, geotechnical, and land use data for map products and, (b) inventory available engineering properties databases. The USGS recognizes the need for standardization and, in some cases, education to provide the American populace, government, and businesses with engineering data that is crucial for safe and resilient infrastructure development and to maintain environmental standards. The broad goals of the project are to assess the use or non-use of this valuable primary data for geologic and derivative map projects, and to establish standardized terminology, map symbology, and best practices for the representation, dissemination (data exchange formats), and storage (database formats) of engineering geology and geotechnical data. Gathering this formative data will enable future extension of the USGS GeMS structure to these data types. We will query by on-line survey the practices and repositories at geological surveys, state departments of transportation, federal geologic, geotechnical, and transportation agencies, and industry groups across the nation. Survey construction is informed by the experiences of Arrington et al. (2020) in their recent survey of the capabilities of state Surveys to implement GeMS. We are aware of a wide range in availability, accessibility, and use of engineering data in mapping across the Nation. At ISGS, geotechnical data compiled from local- to state Departments of Transportation, sewerage districts, utilities, and consultants are vital to our surficial geologic mapping activities. Our wells and borings database, ILWATER (https://isgs.illinois.edu/ilwater), provides a public view of about 228,000 geotechnical borings that were compiled over decades and digitized from the original paper or pdf records, as well as from common digital geotechnical data exchange formats. The records were largely provided to ISGS upon our request as opposed to any programmatic exchange with industry drillers, consultants, and government agencies. The data include descriptive boring logs and, when available, strength parameters, water content, and standard penetration test (SPT) blow count data. The ISGS is currently developing a new database specific to engineering geology and geotechnical data. The database will accommodate ingestion of modern digital geotechnical data exchange formats and support new geotechnical datasets such as those collected by our cone penetration test with hydraulic profiling tool (CPT-HPT) soundings. The database is hardly complete: many records in areas where we are not actively mapping are still to be digitalized or have not been added to in decades. A significant initial task in any mapping project is to manual geospatial verification of the well or boring locations (early entries were often located in our database only to the nearest quarter-quarter-quarter but can be located to within a few feet even from paper records), and estimate absolute elevations for those records that were based on local datums. Once quality-assured, the data provide much more detail (color and standardized textures as well as geotechnical parameters) and more consistent subsurface information than do water well records, although water wells are more numerous and extend deeper. Differentiating till (strength >3 tsf; moisture content typically <15%) from lake sediment (strength <2 tsf; moisture content typically >20%), for example, can be straightforward although local correlations must be determined. We have begun work with consulting companies in Chicagoland to develop a more active and current data exchange, with compiled data to be made available through an ISGS server. Engineering geology maps provide significant value to the public and help inform decisions of land use planning and identification of geohazards. Engineering geology maps include slope stability hazards, subsidence hazards, excavatability, foundation conditions, collapsible soils hazard, liquefaction hazards, and many others. Examples of engineering geology maps that we will present include 1) An early STATEMAP-derivative slope stability map of a degrading watershed east of St. Louis; (2) A regional database of past landslides along the Illinois, Mississippi, and Ohio-Wabash river valleys; 3) A compilation of STATEMAP data in Metro-East St. Louis was developed into a liquefaction susceptibility map for the USGS CUSEC program (Cramer et al. 2017). Our survey of engineering map standards will have two stages: The first-stage survey will be an email sent to agency directors, who may answer the questionnaire as they see fit or may identify the people in their organization best suited to 47 address the survey. The survey will be short with yes/no and multiple-choice responses. The objective will be to broadly characterize use of engineering data and map products by mapping agencies and identify the best contacts for the second- stage survey. Those who do not respond will be reached by telephone. The second-stage survey, using an interactive webform that we are developing, will comprise more detailed questions on maps and map standards, as well as on the source data: the existence of repositories, locational data accuracy, geographic coverage, data exchange formats, and database structures. The surveys will be supplemented by our own on-line and library investigations, and by direct communications with practitioners and agencies. The compiled information will be analyzed to develop guidance for best practices for storage of engineering properties data in relational databases or geodatabases, and their associated benefits for development and storage of map products.