Williams, Gregory

Dr. Greg Williams, P.Eng., is the Director of Water Quality Technology for StormTrap. He has been involved in stormwater treatment technology product development, testing and verification for 15 years, including a decade with Good Harbour Laboratories, a stormwater MTD testing lab. During this time he has been very active in the stormwater community. Currently he is the President of SWEMA, and a member of the WEF Stormwater Institute Advisory Committee, the Stormwater Summit Program Committee, the STEPP Leadership Group and the ASTM E64 Executive Committee. He has co-authored 4 patents.

Titles from this speaker

Sizing of Stormwater Control Measures for Resiliency - The Four Rs

Abstract

In order for stormwater control measures (SCMs) to achieve the required removal they must be sized properly. In many cases sizing involves literally choosing the physical size of the SCM. Sizing an SCM is complicated and there is no standard process. This makes it difficult for stormwater managers to know if the size they have chosen is appropriate. The effects of climate change further increase the uncertainty. The goal of this presentation is to provide stormwater managers with an overview of existing sizing methods so that they can be sure the method they are using is state of the art. It will also present recent thinking on adapting the process to improve resiliency. Stormwater control measures (SCMs) have two basic mechanisms: gravity settling and filtration. These two mechanisms operate differently but they are both less effective at higher flow rates. This means that detailed sizing depends on the specific product or practice but the general sizing process is the same regardless of the SCM. Sizing SCMs is fundamentally a three-part problem: 1.Determine how much rainfall needs to be treated, particularly the maximum expected intensity 2.Determine how much flow will be generated by the expected rainfall 3.Determine how much removal can be expected for the given flows In most cases at least one of these parts, and perhaps all of them, are a black box. Assuming the boxes are functioning properly, which seems to be the case most of the time, this has not necessarily created a problem for stormwater managers in the past. Now that rainfall is known to be changing it is a problem because an unknown process cannot be modified to account for future rainfall. A system sized for today will be undersized in a few years, well before the end of its service life. This presentation will crack the lid on all three boxes and at least partially illuminate them. A detailed discussion could fill a university course but a basic understanding can be achieved in 20 minutes. Different ways to model each aspect will be discussed, along with the strengths and weaknesses of the different options. How models can be adapted to create resilient infrastructure will then be discussed. Section 1: Rainfall will address design storms, using existing rainfall data from the National Oceanic and Atmospheric Association (NOAA) Precipitation Frequency Data (PFD) Server and, finally, modelling rainfall data. Since rainfall data is typically shown as a frequency distribution (see Figure 1) fitting it requires complex mathematics. The model will be based on the generalized extreme value (GEV) family of curves. The presentation will not get into the detailed mathematics but it will describe the thought process. It will also present a basic goodness of fit test, the chi square test. Section 2: Runoff will address the rational method and the probabilistic rational method. The probabilistic rational method has the runoff coefficient, C, as a function of intensity. There is no consensus yet on what this function should be so a few options will be discussed. Section 3: Removal will discuss available removal data, particularly that published by the New Jersey Department of Environmental Protection (NJDEP). The Critical Particle Size Theory (CPST) will be introduced as a way to estimate performance of a system for different particle size distributions (PSDs) based on data from the NJDEP PSD. An example of how to use CPST will be shown. Section 4: Resilience will discuss ways to adapt sizing models to account for recognized changes in rainfall will look at building resilience through the use of climate change models and through different interpretations of NOAA rainfall data. Again there is no consensus on a correct approach, indeed there may be no 'correct' approach, so the focus will be on possible options and their implications.

This paper was presented at the WEF Stormwater Summit in Minneapolis, Minnesota, June 27-29, 2022.

SpeakerWilliams, Gregory

Presentation time

08:30:00

09:00:00

Session time

08:30:00

12:15:00

Session number11

Session locationHyatt Regency Minneapolis

TopicModeling, Resiliency, Stormwater Control Measure

Author(s)

G. Williams

Author(s)G. Williams1

Author affiliation(s)StormTrap1;

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Jun 2022

DOI10.2175/193864718825158453

Volume / Issue

Content sourceStormwater Summit

Word count12

Update on STEPP and ASTM Committee E64 on Stormwater Control Measures

Abstract

If performance data is provided to decision makers it often comes from manufacturers. Much of this data is derived from reputable sources such as the New Jersey Department of Environmental Protection (NJDEP) program, the Washington Department of Ecology Technology Assessment Protocol Ecology (TAPE) program, the International Best Management Practice Database (IBMPDB) or the Canadian Environmental Technology Verification (ETV) website but it is difficult for many decision makers to navigate these sources to confirm the data. NJDEP and Canada ETV both have lab data, but it is presented in different ways and the results do not always agree. TAPE has field data. The IBMPDB contains every kind of data but it is not curated so the quality of the data is not assured. The presentation will provide an update on activities aimed to make assessing performance data easier. It will also describe efforts underway to translate existing region verification programs into a national program, to simplify the job of choosing a stormwater control measure (SCM) A new national source of quality assured information, the Stormwater Testing and Evaluation of Products and Practices (STEPP) program, is leveraging resources from several different organizations in order to improve the way data is produced and reported going forward. STEPP, which was initiated by WEF and now led by the National Municipal Stormwater Alliance (NMSA), will provide stormwater managers with tools for evaluating performance of SCMs and guidance on how to use the tools. The initial focus will be on high priority pollutants of interest such as sediment, trash and plastics, and nutrients, but the vision is to expand the program in the future to include additional pollutants as well as including both proprietary products (manufactured treatment devices, or MTDs) as well as public domain practices, including green infrastructure. The presentation describes the STEPP program, how it is organized and how end users can take advantage of it. 2021 also saw the formation of a new ASTM Committee, E64 Stormwater Control Measures. This is a significant step for the industry, ASTM does not form new committees very often. Prior to this change all stormwater standards were developed by a subcommittee, C27.70 under the committee C27 Precast Concrete. This structure hindered effective standards development and that helped lead to the change. The new Committee has 4 subcommittees that includes Lab Evaluation, Field Evaluation, Apparatus and Research Processes, and Non-point Sources. These subcommittees are currently developing several standards and three new standards have been published so far this year. Additional subcommittees will be added as the committee evolves. This presentation will discuss an overview of the ASTM process and how it is relevant to the stormwater industry. It will also introduce the new standards and describe how the current ASTM work relates to STEPP.

This paper was presented at the WEF Stormwater Summit in Minneapolis, Minnesota, June 27-29, 2022.

SpeakerWilliams, Gregory

Presentation time

11:45:00

12:15:00

Session time

10:45:00

12:15:00

Session number01

Session locationHyatt Regency Minneapolis

TopicStormwater Control Measure, Stormwater Management Design And Analysis, Technology Comparison

Author(s)