|Earth and Rock Works | Earth Retaining Structures | Geotechnical Hazards | Ground Improvement | Structural Foundations | Subsurface Investigation|
|FHWA > Engineering > Geotechnical > Geotechnical Hazards > Mines > Manual for Mine Inventory|
Manual for Abandoned Underground Mine Inventory and Risk Assessment
|Abandoned Underground Mine Inventory and Risk Assessment
Figure 1.1: Process Flow Chart
1.2.1 Establishing An Inventory of Sites: An initial comprehensive site listing should be established for the inventory area. This effort will include review of available records for abandoned underground mines within the inventory area. Field report forms should be discussed and provided to roadway authority personnel for the purpose of gathering field information which might reflect mine-related problems beneath the roadway. Such reports should then be investigated by staff who are involved with the inventory process and are familiar with signs of mine-related problems.
Next all sites should be visited and certain field information should be recorded. Every effort should be made to obtain enough information from one site visit to allow for the risk assessment of the site through Initial and Detailed Site Evaluations as described in this manual. Following this initial site visit, each site shall be subject to periodic monitoring.
1.2.2 Site Monitoring: Interim periodic monitoring will be initiated on all inventory sites. The frequency and extent of required monitoring activities will depend on site conditions as well as they can be identified at this point in the process. All sites will ultimately be periodically monitored on a permanent basis. Frequency of monitoring will be determined on a site-specific basis.
1.2.3 Risk Assessment: The risk assessment portion of this process takes into account two basic factors: 1) the existing site conditions and; 2) the level of the traveling public's exposure to those existing site conditions.
22.214.171.124 Initial Site Evaluation: An Initial Site Evaluation of all sites in the established inventory will be performed by applying applicable site evaluation criteria to available information and field observations. This Initial Site Evaluation process will determine into which of the five risk-assessment site groups each site will be placed. The Low Rating Site Group will be placed under a permanent monitoring program and remain as active files in the inventory program. The Eliminated Site Group will become inactive permanent record files in the inventory program.
126.96.36.199 Detailed Site Evaluation: Detailed Site Evaluation risk assessment will be performed on the Surface Deformation, Mine Opening, and High Rating Site Groups as determined by the Initial Site Evaluations. This work will be performed for each site group in order of their group's priority level of risk. All sites within a site group will be evaluated using site evaluation criteria considered pertinent to the nature of the sites within the group. Detailed Site Evaluation risk assessment will be completed utilizing existing information and information gathered during the initial inventory site visit. The result of the Detailed Site Evaluation process will be a prioritized listing of the sites for the Surface Deformation, Mine Opening, and High Rating Site Groups as defined by the Initial Site Evaluation process.
188.8.131.52 Priority Site Investigations: Priority Site Investigations will be performed on each site within each of the three Detailed Site Evaluation site groups. These site investigations shall be performed in the order of the prioritized listing of the sites for each of the Detailed Site Evaluation risk assessment site groups. All sites within the particular Detailed Site Evaluation risk assessment group will be individually evaluated before evaluation proceeds to sites in the next lower Detailed Site Evaluation group. These investigations will result in Priority Site Recommendations.
184.108.40.206 Priority Site Recommendations: The Priority Site Recommendation shall either specify remediation of defined site conditions, with periodic monitoring to follow construction, or periodic monitoring only. Some recommendations may involve emergency action or temporary road closure. Interim, site-specific monitoring requirements will be specified for the period prior to the implementation of remedial construction or permanent monitoring.
220.127.116.11 Development of Construction Documents: In the case of Priority Site Recommendations requiring the remediation of potentially hazardous conditions, construction drawings, specifications and special provisions will be developed for each individual site. Regardless of the extent of investigations performed, the actual site conditions cannot be fully determined prior to construction. Therefore, this manual places emphasis on flexibility of methods, quantities and project limits.
Existing conditions may change, or new conditions may develop on the site in the period required for contract document development. Guidance is included in this manual for continued site monitoring during Development of Construction Contract Documents.
18.104.22.168 Remedial Construction: Remedial construction shall be performed on those sites where such work is recommended by the Priority Site Recommendations. Close inspection of the work, monitoring of time and materials usage, and accurate record keeping is important during construction. Accurate records will be invaluable for post-construction monitoring and reference in the case of future subsidence conditions occurring adjacent to the project area.
Existing conditions may change, or new conditions may develop on the site during remedial construction. Certain forms of remediation may unintentionally induce additional mine-related settlement. Site monitoring to detect possible changes during remedial construction should be performed.
1.3.1 Expected Benefits:
22.214.171.124 Public Safety: The process will minimize the possibility of sudden abandoned underground mine subsidence in roadways, which could result in fatalities or bodily injuries.
126.96.36.199 Reduced Liability: The process will identify and prioritize high risk sites permitting a systematic response.
188.8.131.52 Budgetary Mechanism: This process will identify levels of risk and associated costs. This information can be used to develop budgets to reduce risks to a predetermined level. This is a proactive process to identify high risk locations. Accordingly, these locations with the highest risk of failure will be identified and remediated first resulting in fewer instances of sudden collapses requiring emergency treatment.
184.108.40.206 Informational Resource: This process will create a new database of information available to all staff. This database will be a tool which can be utilized to avoid or anticipate potentially unstable underground conditions during project planning, design, construction and maintenance.
1.3.2 Governing Principles: Basic principles governing this process include:
Working on the highest risk identified site at all times.
Being as informed as possible before committing resources to a site.
Being prepared to encounter "worst case" conditions for the nature of the site to be investigated or remediated.