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Track 2 Day 1: Pickett Maharaj


Dealing with High Intensity Rainfall Events During Construction

Wednesday March 20, 2019
1:00 to 1:30 pm


Matthew Pickett and Laura Maharaj, Groundwater Environmental Management Services (GEMS)


Over the last couple of construction seasons Groundwater Environmental Services Inc (GEMS) has been answering more and more calls from clients dealing with issues at their active construction projects after high-intensity rainfall events.

The intensity of a rainfall event refers to the amount of rain that falls in one-hour. High intensity rainfall can be up to 100mm in under an hour causing causes localized flooding because of the large volume of water delivered in a short period of time.

The frequency of high intensity events in the GTA is increasing. Regardless of where an active construction site is on the continuum of environmental management and erosion and sediment control, you are going to have to respond to something.

The most common outcome of a high intensity rain event at GTA construction sites are:

  • Flooding & discharge permit exceedances
  • Discharge to the natural environment (a spill)
  • Over-topping of in-water controls

We will share our experiences and what we have learned responding to high intensity rainfall events at active construction sites across the GTA.


Learning Objectives

1. Having permits in place isn’t enough because the question is when, not if, a high intensity rainfall event is going to happen.

2. Key success factors for responding to a high intensity event.

3. What to think about when contingency planning (eg. distance to natural features such as wetlands and watercourses).


Matthew Pickett

Matthew Pickett

Matthew Pickett has more than eight years of experience as an Environmental Professional. He currently leads the environmental monitoring & compliance team at GEMS.

Matthew is responsible for ensuring that clients stay in compliance through the life of their projects. He knows environmental management for construction projects from start-to-finish, from pre-construction assessments, to developing monitoring programs and countless site inspections for both public and private sector project owners.

Laura Maharaj

Laura Maharaj

Laura Maharaj has more than seven years of experience in Geology and Hydrogeology. She is currently the lead hydrogeologist in conducting groundwater assessments for construction dewatering and land development approvals.

These days, Laura keeps busy negotiating short- and long-term Discharge Agreements in municipalities across the GTA on top of Permits to Take Water (PTTW), Environmental Activity Sector Registry (EASR) approvals and Environmental Compliance Approvals (ECA).