25 October 2018

Managing Stormwater Drainage in Urban Karst Conditions

Toby Kessler and Trevor Woodward, Gilmore & Associates, Inc.

Managing stormwater onsite provides groundwater recharge and reduces runoff, but also presents risks.  Sites underlain by limestone and dolomite (carbonate geology) are susceptible to subsidence and water quality impacts.  Urban locations are frequently characterized by variable or poor subsurface conditions, proximity to existing structures and utilities, and environmentally impacted soils.  This presentation will discuss construction and operation of stormwater drainage wells. Specific project examples will be utilized to discuss challenges and opportunities in carbonate and urban conditions.

We will present the procedure for site evaluation and testing, including preliminary hydrogeologic assessment including construction of a test well, performance of an inflow test, groundwater mounding evaluation, and survey of groundwater resources near the site. The presentation will describe the coordination process with civil designers and regulators and the development of system performance requirements and safety factors.  We will discuss the construction of a system of drainage wells and how to perform a system flow test. We will discuss the pre-treatment required before water may flow into the drainage well system. Finally, we will discuss long term performance monitoring, including water levels and water quality. 

Stormwater drainage wells require similar construction and testing requirements as groundwater supply wells, although the function of the wells is reversed. The need for managing stormwater, through properly constructed water quality treatment and stormwater drainage well systems is a growing opportunity for the groundwater industry in Pennsylvania.

Background of Presenters:

Toby Kessler - Mr. Kessler has 19 years’ experience in geology, hydrogeology, and environmental site assessment. He has extensive experience in performing hydrogeologic studies for water supply, sewage impact studies, Phase I and II Environmental Site Assessments, remedial investigations, management of fill for construction projects, groundwater monitoring programs, and municipal review. As the Environmental Services Manager with Gilmore & Associates, Inc., he is responsible for client communication, regulatory interaction, expert testimony, and technical direction of projects and staff.

Trevor Woodward - With Gilmore & Associates, Inc. since 2001, he serves as the point of contact for a variety of municipal and private clients, and handles all aspects of projects from concept to completion. These projects include foundation and subsurface investigations, sinkhole/karst hazard studies, stormwater infiltration investigations, construction materials testing, slope stability analysis, retaining wall design and technical review, forensic investigations, and general consultation on engineering geology matters. As Geotechnical Services Manager, Mr. Woodward oversees office and field activities in the Geotechnical Department.