Project Overview
The Pine Tree Acres (PTA) facility is a municipal solid waste (Type II) landfill in Lenox Township, Michigan. The site has undergone several expansions in the course of operation and currently has a permitted landfill area of over 555 acres. NTH has provided various services for PTA, including air quality permitting, geotechnical engineering, hydrogeologic monitoring and reporting, infrastructure inspections and evaluations, and hydrogeologic exploration. Specifically, NTH conducted several phases of hydrogeologic exploration related to the most recent lateral expansion (“North and East Development”). NTH conducted two different primary phases of exploration in 2007 and 2011. Although NTH did not prepare the final hydrogeologic investigation report the accompanied the formal construction permit application for this latest expansion, the information provided by our exploration was important for evaluating potential options and defining the basic design configuration of the landfill cells within the expansion area.
Project Scope
NTH drilled test borings and installed piezometers at strategic locations within and around the perimeter of the proposed expansion area. The exploration locations provided information on geologic stratigraphy and groundwater occurrence and levels that was crucial for designing the landfill cell layout and floor grades. A critical consideration was whether the saturated fine-grained granular soils would be considered a groundwater unit for monitoring purposes and as a basis for establishing vertical isolation. NTH conducted a long-term (24-hour) pumping test to determine the productive capacity of this unit and develop hydraulic parameters. The pump test was performed using a pressure transducer and electronic datalogger installed in adjacent piezometers. Analysis of the pump test data by NTH provided the hydraulic parameter estimates and also the approximate extent of influence of the pumping well.
Our exploration and evaluation also included extensive laboratory testing and classification of cohesive soils encountered in the subsurface. This information was used to demonstrate that the shallow deposit of cohesive soils meets the definition of “natural soil barrier” as defined by MDEQ.
Client Benefit
NTH evaluated available options for maximizing the available airspace for waste disposal based on evaluation of the subsurface stratigraphy and groundwater conditions. Our exploration and testing also contributed to the final, approved Part 115 Construction Permit Application for a significant lateral expansion of the PTA landfill.
