Unique Experience

About Grist

Halliwell previously worked for over eight years as an embedded consultant within the Philadelphia Water Department (PWD) Green Stormwater Infrastructure (GSI) Implementation Unit, Office of Watersheds, and Planning & Research Unit. This experience gives Grist unparalleled knowledge of the PWD standards and procedures, in both the private development and public sector work.

​Before consulting in these roles for PWD, Halliwell designed sustainable site/civil projects for commercial, residential, and institutional developments. Innovative stormwater management featuring various applications of GSI and Low Impact Development (LID) techniques to manage stormwater were integral parts of these designs.

Grist is a green infrastructure studio dedicated to providing environmentally sustainable and restorative engineering designs. We focus on projects where green design is important to the client and often where it is a driving force for the project. Because of our small size, we can provide these services at a low cost to the client while maintaining exceptional focus and quality.


Thomas J. Halliwell, PE, LEED-AP is Principal at Grist.​  He has over 20 years of experience in civil engineering, site development, and green infrastructure design.