The Director shall require a soils investigation report prepared and certified by a professional engineer duly registered in the State of Maryland to correlate surface and subsurface conditions with the proposed grading, site and building plans. The Director may require a soils investigation report depending upon slopes, anticipated characteristics of soil, drainage characteristics and the like. The results of the investigation shall be presented in a report by a professional engineer which shall include, but need not be limited to, data regarding the nature, distribution and supporting ability of existing soils and rock on the site and include conclusions and recommendations for grading requirements and erosion control including recommendations to insure stable soil conditions and groundwater control applicable. The Director may require supplemental reports and data by an engineering geologist as might be deemed necessary. Recommendations included in such reports and approved by the Director shall be incorporated in the grading plan or specifications.