PSA - Arcadis - North Station Well #1 Replacement Design

Home Browse Search

An Arcadis hydrogeologist will be on site to direct the well drilling contractor, record the geologic materials encountered during drilling, and collect geologic samples of the aquifer. Core samples of the subsurface will be collected continuously from ground surface to the total depth of the boring. A number of key samples from the anticipated screened interval of the production well will be retained, containerized, and submitted to a geotechnical laboratory for grain -size distribution analysis. At least one geologic sample will be collected for every five foot interval through the anticipated screen zone of the production well. Arcadis will contract directly with the geotechnical laboratory to conduct the grain - size analysis. We have assumed a $500 budget based on past experience, which will need to be confirmed with the selected drilling contractor. Upon reaching the total depth of the boring, a temporary monitoring well will be installed in the borehole for collection of a water quality sample. The temporary monitoring well will be installed by pulling back the rotosonic drill casing and allowing the natural formation materials to collapse around the well screen. The monitoring well will then be developed until water is free of sediment and turbidity. A water quality sample will be collected and submitted to analytical laboratory. The list of water quality parameters to be analyzed will be developed prior to drilling based on discussion with the City. It is understood that elevated concentrations of ammonia have been problematic in several of the existing production wells. Ammonia will be included in the water quality parameter list, but an assessment of the cause of any detected ammonia concentrations would be beyond this scope of work. The water quality sampling results will be presented to the City and any regulatory exceedances will be noted. It is assumed that costs for the analytical laboratory will be billed directly to the City. Upon completion of the drilling and sampling, the temporary monitoring well will be removed and the borehole will be sealed with bentonite grout. A well log will be produced that summarizes the geologic information from the test boring and will be submitted to the City. Task 6. Construction Drawings Arcadis will prepare detailed drawings to show the general scope, extent and character of the work to be furnished and performed by the Contractor. The plans will show site plans, mechanical equipment configuration and layout, piping layouts and details, structural components and details, electrical equipment and connections, and equipment and schematics for process instrumentation and control. Multiple disciplines will be shown on a drawing for simplification. It is assumed that the City has an existing site plan available for our use and no additional survey work is required. These documents will stipulate: well materials; well diameter; well depth; type of screen; length of screen; screen slot openings; grouting requirements; and well development and performance testing requirements. Specifically for the well design, Arcadis will use the information from the above tasks to design the production well. The well will be designed to account for the operational objectives for the well and to maximize long-term performance and longevity. Design parameters will include design considerations for the well screen, including slot size, gravel pack size, screen length, percent open area, and entrance velocity, along with the casing and borehole diameters and grouting requirements. The design will include the necessary sanitary protection and will meet IDEM regulatory well construction requirements specified 327 IAC 8-3.4. Arcadis will estimate the design capacity and the range of operating water levels from geologic information from the test borings and the evaluations performed as part of Task 1. Page 4 (Exhibit A— Engineer's Services) EJCDC E-500 Agreement Between Owner and Engineer for Professional Services Copyright 0 2008 National Society of Professional Engineers for EJCDC. All rights reserved.