Preparing the Groundwork for Cell 2: Key Pre-Design Activities

Designing a new modern landfill waste disposal area (e.g., cell) is rarely straightforward, particularly when it must be constructed within a narrow valley between existing cells and under a tight timeframe. Constructing Cell 2 at Cecil County’s Central Landfill required careful preliminary investigations to identify critical design constraints early and to minimize the potential for design or construction delays and costly field changes.

This blog is Part 1 of a two-part series and focuses on the pre-design activities that shaped the Cell 2 design, including test pit investigations, anchor trench location, geotechnical exploration, and the key design and operational challenges identified before progressing the design.

Understanding Historical Filling Operations within Cell 1

Early test pit investigations confirmed existing cover conditions within the limits of the unlined Cell 1 where the proposed Cell 2 liner system was to overlay. The primary objective was to evaluate the existing thickness of soil cover and to what extent existing soils could be excavated and graded without disturbing underlying waste that was already in place.

Test pits confirmed that Cell 1 was constructed as a trench fill, consistent with historical aerial photographs and pre-RCRA Subtitle D landfilling practices. A thick layer of soil was encountered along the side slopes, where material had originally been placed to form a soil berm for the trench fill configuration. Understanding these conditions allowed for controlled excavation along the side slopes to establish uniform grades without disturbing the underlying waste.

Anchor Trench Location Study

The existing and future cell limits, as defined by an anchor trench, was another critical pre-design consideration. Confirming the precise anchor trench location and depth of the existing anchor trench played an important role in developing accurate liner tie-in elevations, locations of the existing anchor trench and grading plans for the Cell 2 area. The depths of these features were compared with groundwater elevations to ensure sufficient separation.

Geotechnical Investigation

A comprehensive geotechnical investigation evaluated subsurface conditions across the Cell 2 footprint. The program included soil borings, sampling, laboratory testing for engineering properties of existing soils, and groundwater monitoring.

The results showed a combination of fill soils overlying natural clay, silt, and sand layers typical of the regional geology. Groundwater levels varied across the site, reinforcing the need for careful floor grading and liner system design elements to maintain regulatory separation. The geotechnical findings allowed for informed slope stability analyses, helped define appropriate side slope geometries, and supported development of a grading plan that balanced long-term stability with airspace optimization.

Key Design Challenges Identified Early

The pre-design investigations revealed several technical constraints that shaped the Cell 2 design:

• Delineation of existing waste limits to minimize waste excavation and relocation to establish maximum and minimum liner system slopes
• Analysis of potential waste settlement within areas of Cell 1 being overlayed with the Cell 2 liner system
• Liner tie-in constraints paired with groundwater separation requirements
• Modification of existing Cell 1 leachate conveyance system to maintain functionality during construction and post construction
• Tight vertical tolerances for cell floor and sump elevations that maximized airspace
• A narrow valley section, requiring minor excavation to establish uniform 3:1 slopes and create a wider cell floor for ease of future operations
• Maintaining long-term slope stability while maximizing airspace

Identifying these challenges early allowed the design team to develop solutions proactively rather than reactively, reducing the risk of changes and cost overruns during construction.

Looking Ahead

The pre-design activities for Cell 2 provided the foundation for every major design decision that followed. By investing in early investigations and clearly defining constraints, the project team identified a clear path for the design and construction of Cell 2.

In Part 2 of the blog, we will explore how these early findings guided the critical elements of design and ultimately the successful construction of the project. A project milestone timeline is presented below:

• Pre-Design, Design, and Permitting: August 2022 – September 2023
• Bidding/Award: October 2023 – April 2024
• Construction: May 2024 – February 2025
• Certification Report: February 2025
• MDE Approval of Report: April 2025

For more information regarding our firm’s solid waste management services, contact Steve Lezinski, Vice President.