Ninyo & Moore provided geotechnical and environmental services for the Hotel College Academic Building project to be located at the UNLV campus. The project will include demolition of existing structures at the site and construction of a 4-story education facility that will be approximately 260 feet long and approximately 150 feet wide. The proposed building will be of steel-frame with some structural masonry. The building will be founded on conventional spread foundations with a concrete slab-on-grade floor. Additional site improvements for the project may include areas of asphalt concrete (flexible) and/or concrete flatwork, curbs, and gutters; and masonry block screen walls and low-height masonry block retaining walls. The purpose of our evaluation was to assess geotechnically related considerations pertaining to the project and to provide recommendations for design and construction of proposed improvements.

Project Challenge: As a result of shallow groundwater conditions at the site, dewatering for the sewer tie-in was anticipated. The chemical analyses of groundwater reported a slightly elevated level of nitrate that would have required treatment of dewatering effluent prior to discharge in the sewer or storm drain systems. This lengthy process of NPDES permitting would add an unacceptable delay to the project.

Innovative Solution: In order to avoid a long permitting process, the State was approached with an alternative discharge solution. Since the only chemical of concern was a low nitrate concentration, the State granted a request to allow a combination of surface discharge from dewatering for localized irrigation, and/or use of the discharge water for surface dust control application on and off-site for the project duration.

Services: Ninyo & Moore conducted an environmental and hydrogeologic investigation to develop information for dewatering design estimates and to prepare a National Pollutant Discharge Elimination System (NPDES) permit application for possible dewatering of the excavations. Ninyo & Moore’s services included installation of a temporary monitoring well, collection and chemical analysis of groundwater samples, and performance of hydrogeologic tests on the well to estimate the aquifer conditions at the site. Ninyo & Moore performed multiple hydraulic displacement tests to estimate aquifer characteristics in the vicinity of the proposed excavation. The hydraulic conductivity values were incorporated into a numerical, finite difference groundwater model to simulate the expected water level changes caused by various pumping scenarios under the modeled conditions. Ninyo & Moore’s geotechnical services included drilling, logging, and sampling of five exploratory borings to up to 75 feet deep; performance of a Refraction Microtremor (ReMi) survey; performance of laboratory tests on representative soil samples to evaluate engineering characteristics; data compilation and analysis; and preparation of a geotechnical report presenting the findings of our study and recommendations, including recommendations regarding demolition, earthwork, caliche considerations, temporary excavations, design and construction of foundations, retaining walls, concrete flatwork, flexible pavement sections, and other exterior site improvements.