William Gonwa, Ph.D.

Grass Roofs are Becoming Popular Energy Savers Around Milwaukee

Living Architecture Monitor  

2018-07-12

"It's a great idea. You get multiple benefits," said William Gonwa with MSOE. From the ground, you'd never know there's a garden on the roof of MSOEs Grohmann Museum. Gonwa says it does so much more than look pretty.

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Why 100-year rainstorms occur so frequently

Central States Water Environment Association Collection System Seminar  

2022-03-01

Are the Rational and NRCS CN/UH Methods for Estimating Peak Flow Rates in Rural Areas Accurate?

ASCE Wisconsin Section Spring Technical Conference  Virtual

2021-03-05

Accuracy of NRCS Runoff and Curvilinear Unit Hydrograph Approach for Estimating Peak Flow

Stormcon 2019  Atlanta, GA

Does the Rational Method for Estimating Peak Flow Rates Still Work?

Stormcon 2018  Denver, CO

City of Wauwatosa Grant to Develop Design Guidelines & Analysis Tools for Green Alley with significant longitudinal

MSOE 

2021

Water Environment Research Foundation Grant to Document the Effectiveness of the Greencastle

Indiana Private Property I/I Reduction program 

2007

Grant to Design, Build, and Monitor a Pervious Pavement Parking Lot in the city of Milwaukee

USEPA 

2006

Grant to Document the Effectiveness of the Greencastle, Indiana Private Property I/I Reduction Program

USEPA 

2005

Design of Residential Storm Water Infiltration Practices

Milwaukee Metropolitan Sewerage District 

2005

MSOE Pervious Pavement Parking Lot

Milwaukee Metropolitan Sewerage District 

2004

Miller Brewing Bioretention Swale and Rain Garden

Milwaukee Metropolitan Sewerage District 

2003

Efficient Real Time Control and Operation of Interconnected Wastewater Collection Systems

Milwaukee Metropolitan Sewerage District 

1993

Analysis and Effective Design of Green Alleys with Significant Longitudinal Slope

Gonwa, W.S.

2022-03-03

Design guidance for permeable pavement systems advise constructing the storage layer subgrade as flat as possible or with a series of cells if the subgrade is sloped greater than 2% (Wisconsin DNR Technical Standard 1008). What is the best way to design the storage layer if there is a significant slope and how can one analyze system performance if there is a significant slope? The City of Wauwatosa in Wisconsin requested the Milwaukee School of Engineering (MSOE) look into the matter by investigating the hydraulic conductivity and porosity of potential subgrade materials, creating a spreadsheet-based tool to analyze the performance, and developing design guidance for proposed sloped green alleys within the city. MSOE constructed a 12-foot-long variable slope flume into which potential subgrade materials could be loaded. Based upon water level measurements along the length of the flume, hydraulic conductivity was computed using the Hele-Shaw solution for unconfined flow in a sloped aquifer. A sieve analysis determined the gradation of the aggregate. Porosity was measured using standard ASTM methods. Locally available drainage stone aggregate sizes of 3/8” chips, No. 1, No. 2, and No. 3 stone were characterized. The analysis spreadsheet has two steps. The first computes the subsurface water table profile, maximum depth, and storage at different flow rates for a two-layer subgrade. The second uses storage routing to route the inflow hydrograph through the subgrade. Analysis results turns the typical design upside down! It is most efficient to place smaller aggregate below larger aggregate. Simulation results for storm sizes ranging from 1-year to 100-years indicate a 4 to 9 fold reduction and 24 to 54 minute delay in peak discharge rate to the storm sewer system with greatest effectiveness during small storms. The Excel spreadsheet design tool is available free-of-charge to interested parties.

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Improving Model Hydrology Accuracy Using Antecedent Moisture Modeling: Reparameterization Update and Case Study

Edgren, D., Czachorski., Gonwa, W.S.

2022-03-02

Developing simple and accurate hydrologic models for wet-weather sanitary sewer flow has long been enigmatic for the engineering community. Sanitary sewers respond to precipitation at various scales from hours to weeks to months. The flow response to precipitation is highly dependent upon antecedent moisture conditions and seasonality. The Antecedent Moisture Model (AMM) was presented at ICWMM in 2021 by Robert Czachorski. This model is an empirically calibrated method which models a capture coefficient which varies by antecedent moisture and by season. AMM has been particularly successful in modeling sanitary sewer infiltration, for which prior methods perform poorly. A working group of AMM users has reparametrized the original model to improve interpretability and ease of use. The reparametrized model is designed to be more intuitive, scale independent, and timestep independent, while remaining essentially equivalent to the original model. These changes will be briefly presented and explained. This presentation will also provide a case-study for the City of Joliet. The City’s model dating from 2015 was calibrated using the RTK method. The model was being used to size a sanitary storage tank for its Long-Term Control Plan (LTCP), which had been planned for over a decade. However, it was determined that the RTK method was unable to adequately calibrate to basins which had widely varying amounts of infiltration depending on antecedent moisture condition. After re-viewing alternative hydrologic methods, it was decided to recalibrate the model using the AMM method. The recalibrated model resulted in a much better calibration. With the newly calibrated model a Long-Term Continuous Simulation (LTCS) was run using historical data which showed that in fact no sanitary storage would be required. Using this evidence the City was able to obtain regulatory approval to remove this requirement from its Long-Term Control Plan, saving the City an estimated $8 million.

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Fluid Mechanics: Bernoulli's Equation

Gonwa, W.S., Arias, M.

2020-08-04

This module forms part of a larger series that examine the various aspects of the General Energy Equation. This particular module deals specifically with Bernoulli's Equation, which is a subset of the General Energy Equation. The module starts by leading the student through the development of Bernoulli's Equation. Then Bernoulli's Equation is combined with the Continuity Equation and the Q-A-V relationship to allow students to show students extensions of Bernoulli's Equation within the practice of engineering. Students are then introduced to Hydraulic and Energy Gradelines and piezometric head. To culminate, students are led through applications of Bernoulli's Equation. Each of the four sections contains calculations to help students understand concepts and apply Bernoulli's Equation with a final learning activity designed to challenge students at higher cognitive levels. The final activity involves having students create a video that demonstrates their understanding of Bernoulli's Equation and includes a stu

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Experimental Apparatus for Teaching Pipe Networks and other Hydraulic Phenomena

Gonwa, W.S.

2020-05-19

This paper describes a versatile apparatus suitable for teaching the principles of hydraulic grade lines, parallel and serial pipe analysis, multi-loop pipe network analysis, and surge tanks in courses such as fluid mechanics, water resources engineering, and water distribution system design. The apparatus can be configured in many different ways, depending upon the principle being taught.

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Using Full Factorial Analysis to Enhance Water Quality Monitoring Programs

Gonwa, W.S., Byers, H.L., Koltz, B.J.

2008 Statisticians use a group of techniques collectively called "Design of Experiments" when designing a sampling program. A formal experimental design can multiply the information gained from a sampling program many times over an informal design. Full Factorial Regression Analysis is one such technique particularly useful for designing stream or river sampling programs. Full Factorial Regression Analysis collects all sampling data in n-orthogonal dimensions at two or more levels in each dimension. For example, upriver and downriver from a potential contaminant source could form one of the dimensions, collected at two levels. Wet weather and dry weather could form another dimension, also at two levels. Collecting data in orthogonal patterns allows sample to be used in multiple paired comparisons and maximizes the ability to determine the causes of data variability. In addition, Full Factorial Regression Analysis permits assessment of factor interaction. This paper provides a background on the Full Factorial Regression Analysis technique used to design a water quality sampling program and analyze the data. It discusses the use of regression analysis to process data and overcome the problem of missing samples. Lastly, it highlights two sampling programs designed and analyzed with Full Factorial Analysis. The two programs, one conducted on the Mississippi River by the City of Rock Island, Illinois and the other conducted on the Illinois River by the City of Peoria, Illinois were designed to document the effects of combined sewer overflows on water quality in receiving waters with multiple pollution sources.

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Private Property I/I Control Program in Greencastle, Indiana

Gonwa, W.S., Nitka, J., Morrow, G.

2008 The City of Greencastle initiated an infiltration/inflow (I/I) reduction program to reduce I/I from private property sources in 2003. Greencastle's I/I policy requires certified inspectors to document that privately-owned properties do not contribute excessive rain water to the sanitary sewer systems. Residential properties are inspected upon requests for a new water service, which typically occurs upon change of ownership. Non-residential properties were required to be inspected within two years of program initiation and have been completed. If an inspection finds a defect, property owners must either fix the defect immediately or apply for a waiver. A waiver can only be granted when fixing the defect is impractical or too costly. Compliance inspections typically cost 30 to 50 and are scheduled and paid for by the homeowner.The policy is making a difference. After just a few years in effect, WWTP operators noted lower average daily flows and lower peak flow rates. Prior to implementing the policy and companion public side I/I removal efforts, rain events would often cause peak flows of 16 million gallons per day (MGD). Currently, heavy rains are needed for peak flows to exceed 5 MGD. Before the policy, the treatment plant would need to treat increased flows for several days and sometimes weeks after a rain event. Now, operators observe that treatment plant flows return to normal within 24 hours. Manholes that frequently surcharged to the surface prior to implementing the policy now do not surcharge. The City views the policy as an unqualified success at reducing I/I in the collection system.The United States Environmental Protection Agency (USEPA) and the Water Environment Research Foundation (WERF) jointly funded a program to document the effectiveness of the I/I reduction program. In the spring of 2007, Greencastle installed flow metering at four of locations that had been metered prior to initiating the I/I reduction program which allowed a comparison of pre- and post-rehabilitation flow rates. This paper reviews the design of the program, provide an update on the implementation of the program, and presents data documenting costs and benefits.

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Preventing Increased Infiltration/Inflow from Residential Storm Water Best Management Practices

Gonwa, W.S., Ellis, S.D.

2006 This paper discusses design criteria and guidelines for the placement of three types of residential storm water best management practices: rain gardens, downspout extenders, and rain barrels. Guidelines are needed to prevent unintended increases in private property infiltration and inflow (I/I). These guidelines specifically focus on soils and construction practices typical of the Milwaukee, Wisconsin area. The rain garden investigations were designed to determine the recommended distance between a raingarden and a house's sewer lateral. The field experiments consisted of a series of 100 square foot simulated rain gardens placed at increasing distances from the sewer lateral. Rising groundwater levels or soil moisture content at the sewer lateral during a test indicated the potential forincreased I/I. As a result of the field experiments, the investigators recommend placing a rain garden at least 10 feet away from the sewer lateral or house foundation in the silty clay soils typical of the Milwaukee area. Placing test rain gardens at this distance resulted in no impact on soil moisture at the sewer lateral. If groundwater mounding occurs, it is unlikely that any increase in infiltration into leaky laterals will occur within the critical time frame for sanitary sewer overflows. The downspout investigations were designed to determine the recommended length of a downspout extender. The field experiments consisted of simulating rainfall discharge through downspout extenders of different lengths. Increased flow in the house's foundation drain indicated the potential for increased I/I. Downspout extenders that discharged at least 5-feet away from the house foundation resulted in no increase in drainage to the house foundation. As a result of the field experiments, the investigators recommend using a minimum of 5-foot-long downspout extenders in the siltyclay soils typical of the Milwaukee area. Ten-foot-long extenders are preferred. The rain barrel investigations were designed to determine guidelines for draining rain barrels into planting beds adjacent to house foundations. The field experiments consisted of simulating rain barrel discharge through weeping hoses of different lengths while monitoring the discharge through the foundation drain. Increased flow in the house's foundation drain indicated the potential for increased I/I.

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Efficient Real-time Control and Operation of Interconnected Wastewater Collection Systems

Gonwa, W.S.

1993 One of the most cost effective methods for limiting sewer overflows and flooding is to actively control the sewer system, operating it to fully utilize available storage, conveyance and treatment capacity. Such requirements are now included in sewerage utility discharge permits. Installing regulators, such as moveable sluice gates and weirs, allows sewer operators to control flows, but can cause problems such as increased risk of flooding. These regulators require efficient control logic to meet operational objectives and constraints. Algorithms are developed to solve several typical control problems in inline and diversion gate control. One algorithm controls an inline gate to maintain a desired flow rate or upstream water level. Another algorithm determines the diversion flow required to achieve a desired flow rate or water level in the main sewer. Another set of algorithms determines required flow rate at a control structure to achieve a desired flow rate or water level at some downstream location where substantial delay exists between the control action and its effect. All algorithms are based on water level measurements and are implemented with a minimum of mathematical and controller complexity. Fuzzy control methods are proposed where conflicting operational objectives and qualitative information exist. Portions of the Milwaukee Metropolitan Sewerage District (MMSD) collection systems were modeled to assess algorithm performance. The few hydraulic models theoretically capable of simulating a sewer system subject to control are unstable and execute slowly. An improved model, based on the zero-inertia approximation, was developed to test control algorithms. The zero-inertia model assumes no inertial components in the governing equations for flow, the St. Venant equations, but can model backwater effects and flow reversals. The recommended algorithms are stable and can maintain elevated flow rates and water levels with little risk of flooding. Fuzzy control successfully balances conflicting objectives and manipulates qualitative information. The potential for substantial benefits from improved control of the MMSD collection system is demonstrated. The zero-inertia method is demonstrated to be a stable, accurate, and rapid method for simulating sewer systems subject to control.

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A Modified Diffusion Equation for Flood Propogation in Trapezoidal Channel

Gonwa, W.S., Kavvas, M.L.

1986 This study on the diffusion equation was performed to gain new insight into the adequacy of the analytically solvable linear diffusion equation which is used as an approximation to Saint-Venant's equations for flood routing in open channels. The derivation of the diffusion equation was approached assuming a variable trapezoidal channel cross-section, variable channel slope, constant lateral inflow, a generalized velocity—depth relationship and the diffusion approximation to the full Saint-Venant's momentum equation. A new modified diffusion equation was obtained which theoretically accounts for channel and wave variations resulting in new non-linear expressions for the wave celerity and diffusion coefficients. Numerical testing on a linearized version of the modified diffusion equation shows that the assumption of constant values for the parameters of the diffusion approximation yields inadequate flood routing results. Since the assumption of constant wave celerity and constant diffusion coefficient in the diffusion equation amounts to the linearization of the equation, the numerical results of this paper show that the linear form of the diffusion equation is inadequate for flood routing. Therefore it is necessary to consider the non-linear form of the diffusion approximation to Saint-Venant's equations as an approximate model for flood routing.

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