Providing Geological, Environmental, Water Supply, Geotechnical & Mapping Services
Preliminary hydrogeologic studies are conducted for clients proposing to subdivide their properties. Located in rural or developing areas, these properties must utilize on-site septic systems and water supply wells. The studies identify the appropriate size for the proposed subdivisions that will provide the recharge area needed to dilute the additional nitrate loading from the proposed on-site wastewater treatment systems to acceptable concentrations within the groundwater. Existing documents are reviewed to obtain information on the soils, geology, groundwater recharge rate and groundwater quality. Representative samples are collected from water supply wells in the area to determine the background nitrate concentrations in the groundwater. A mass balance model is then used to determine the acreage required to dilute the applied nitrate concentration. This information is generally required by the Township to approve the subdivision.
Township ordinances required the delineation of alluvial and/or hydric soils along waterways as part of their preliminary development review process. The delineations are conducted using existing site plans, topographic maps and on-site soil sampling. Criteria for delineating alluvial soils include soil characteristics, geomorphology, topography, and stream mechanics. Hydric soils are classified using the Munsell soil color chart following the procedures specified by the Federal Manual for Identifying and Delineating Jurisdictional Wetlands.
Aerial photograph stereo pairs were used to identify the geologic contact between a carbonate valley and adjacent crystalline bedrock. The location of the contact was instrumental in preparing development and surface water management plans.
Aerial photograph stereo pairs were also used to evaluate the historic locations of surface drainage features and wetlands. A local citizens group raised questions regarding the placement of fill at a large residential development. The photos were used to map historic features and approximate the acreage of filled wetlands.
Aerial photograph stereo pairs were used to identify photolineaments. These lineaments may represent subsurface features such as fracture zones within the bedrock. The findings from the fracture trace mapping are used to identify favorable locations for water supply wells and groundwater monitoring wells. Fracture trace analysis can also assist to identify preferential pathways for groundwater flow or contaminant transport.
Carbonate assessments involve an understanding of the local bedrock geology, topography and hydrogeology to identify potential sinkhole prone areas. Visual observations, aerial photographs, historic knowledge and available documentation assist in identifying sinkholes and depressions. When a more detailed evaluation is necessary, geophysical surveys and exploratory investigations can be employed. In these cases there is no single technology that will identify sinkholes under all geologic conditions, however, the proper geophysics for the conditions can optimize exploratory borings and provide a considerable cost advantage.
Wetland delineations have been conducted on numerous sites varying in size and complexity. The delineations were performed using the 1989 Unified Federal Methodology and 1987 Corps of Engineers Wetland Delineation Manual criteria.
Taylor GeoServices, Inc.