Radar Reflectivity Analysis - A New Tool in the Sewer Collection System Arsenal

With a D- grade from the American Society for Civil Engineers, there's no question that America's sewer systems are in rough shape. The EPA estimates that there are 40,000 Sanitary Sewer Overflows (SSOs) each year. (That's when systems overflow spewing raw sewage into streets, rivers and basements.)

The most common cause of Sanitary Sewer Overflow stems from heavy rainfall events which cause massive infiltration of stormwater into sewerage lines. Blockage or rupture of sewerage lines also contribute to SSOs.

Municipal system owners look to civil engineers to determine the causes of SSOs and to design the most cost effective approach to eliminate them. The engineer's first step is often to perform a study to determine the causes and sources of the inflow and infiltration. An I/I study models the sanitary system, including determining how wet weather (especially those heavy rainfalls) will affect the system.

When it comes to wet weather responses, the antecendent moisture level can have a huge and vaying impact on the system's performance. From Wikipedia, antecedent moisture is a term that describes the relative wetness or dryness of a sewershed, which changes continuously and can have a very significant effect on the flow responses in these systems during wet weather. Antecedent moisture conditions are high when there has been a lot of recent rainfall and the ground is moist. Antecedent moisture conditions are low when there has been little rainfall and the ground becomes dry. So when you get down to it, a model that does not take antecedent moisture into account in determining a sewer system's capacity to respond to wet weather isn't really very accurate (or useful!) at all.

For more reading about hydrologic models that accurately account for antecedent moisture impacts, check out this overview of i3D, an antecedent moisture model:

Hydrologic model i3d white paper

View more documents from OHM Advancing Communities.

But wait, there's more! OHMers Tim Kuhns and Robert Czachorski recently presented a paper at the Water Environment Federation's national Collections Systems Conference. The case study outlined an inflow and infiltration modeling study in Scio Township, Michigan. The project demonstrated the value of a comprehensive approach that includes a highly accurate hydrologic model and radar reflectivity data to identify and correct a rainfall measurement error.

In the paper and presentation, Tim shares several interesting findings for a comprehensive approach to modeling:

-A continuous model that accurately predicts flows can be used to identify anomalies with rainfall and flow measurements. An event based model may not as easily identify these types of errors.

-A thorough evaluation of all error components (model prediction, rainfall, flow) should be completed for major calibration events to ensure model accuracy and confidence in the model results.

-Free and readily available radar reflectivity data can be used without pre-processing to assess the accuracy of rainfall measurements.

How Hydrologic Modeling and Radar Rainfall Analysis Can Overcome Rain Gauge Errors in I/I Studies

View more presentations from OHM Advancing Communities.

Opportunities and Football: Our Love/Hate Relationship

The article below appeared in the June 24th edition of the Livonia Observer:

There are two things that get John Hiltz really excited. One is his beloved and beleaguered University of Michigan football team. The other is the word opportunity. Especially the opportunity he sees for his nearly 50-year-old namesake company, Orchard, Hiltz McCliment Inc. of Livonia.

Known as OHM, Orchard, Hiltz McCliment Inc. was founded by former city engineers John E. Hiltz and Melvin “Ernie” Orchard as a municipal engineering firm.

When the company opened its doors in 1962, it had one client, the city of Livonia. OHM's staff of 20 worked on a landmark project for the city: designing 40 miles of sanitary sewer to bring municipal sewer systems to homes originally on septic tanks. This was the foundation of Livonia's urbanization and OHM's growth.

Fast forward 48 years and today OHM has offices in three states and works for clients across the country. And the services have expanded, too. Nearly 170 employees are on staff, including architects, civil, electrical and mechanical engineers, planners, urban designers, surveyors, grant writers, LEED-accredited professionals and information technology experts.

But it wasn't always an upward climb. Founder and former company president Ernie Orchard recently commented about the current economic recession: “What's happening now? This is kid's play. In 1980, there were companies that had to cut every employee and just the owners were left. OHM went from 45 people to 20.”

As the country recovered, OHM prospered. Orchard said: “We were lucky. We came out of the recession debt-free and were able to land a lot of new accounts. There was big growth after that.”

The new millennium's recession was already hitting Michigan hard when John Hiltz became president in 2009. At the same time, OHM's board of directors approved a strategic plan to double the economic value of this Michigan-based firm over the next five years. John looked hard for opportunity.

He found it in an unlikely place for a die-hard Wolverine: Columbus, Ohio. In the summer of 2009, OHM opened a Columbus office with a former staff member who had relocated to the city. Within a few months, leaders from OHM were in negotiations to expand operations by merging with a new company — one that Hiltz believed would bring that much-desired “opportunity.”

That new company was Bird Houk Collaborative, a 20-person firm offers architecture, urban planning and real estate economic analysis. Company owners had aspirations to expand the mid-Ohio firm's geographic reach with its urban planning expertise, but that effort grew difficult amid a decline in construction projects.

OHM's mission is Advancing Communities. Bird Houk billed themselves as The Placemakers, committed to making places better for people. Knowing that the challenge of integrating company cultures is where most mergers fail, Hiltz recognizes his good fortune in such a close match.

“I feel totally blessed to have come across Bird Houk, which has so many of the same values and vision,” he said.

In May, the two firms celebrated the merger with a tailgate-style party at Bird Houk's metropolitan Columbus office. Because most of Bird Houk (now renamed Bird Houk, a division of OHM) staff members attended Ohio State University, the party's theme poked fun at the U-M and OSU football rivalry with the tagline, “A House Divided? Services United!”

“I know there'll be one day each year when we're bitter enemies,” said Hiltz, laughing. “Fortunately, during the other 364 days, we're totally united in our focus to help communities redevelop because of shifting economic bases.”

Are You Sure You're Getting Your Money's Worth? VE it!

This week we're talking briefly about an engineering concept that may not be widely known but is incredibly important, especially when it involves large, high-profile public works projects.

Value Engineering
Jim Marcinkowski, PE, Senior Design Engineer, with OHM’s Transportation group is a sought-after member for value engineering teams. Value engineering is an independent analysis of a proposed project, using a systematic approach to validate the effectiveness and cost of the proposed project plan.

Bottom line? When you're a project owner and the public is footing the bill, you want to make sure that you're getting the most value for the millions you're spending.

Here's a look at one of Jim's more iconic value engineering projects: the ramp rehabilitation at St. George Staten Island Ferry Terminals in New York.

The greater Ferry terminal area is a concentration of multimodal elements including bus, rail and automobile traffic. While the Ferry terminal itself had recently been reconstructed, the elevated bus terminal and adjacent ramps were in poor condition. Passengers disembarking from the ferry had to walk through a dark, dingy area, where water seeped through the dilapidated joints of the bus terminal deck above, to rain lead-infused drips onto their heads. Additionally, traffic surrounding the terminal area was congested, creating lots of delay for circulating buses and automobiles.

The City had planned a ramp repair project to be delivered as design/build that would keep the facility open throughout construction. At $175 million, this was the largest ARRA project in the US and the City wanted to be sure it was spending The People's dollars wisely. Enter, the value engineering team.

The value engineering study reviewed the conceptual design for the rehabilitation of ramp structures at the terminal and examined the methodologies to achieve the best value for all stakeholders. As a member of the VE team, OHM’s Marcinkowski analyzed all project documentation. Using his expertise in construction staging and maintenance of traffic he provided significant recommendations to maximize traffic flow to the ferry terminal and surrounding neighborhood, including a $4 million cost saving idea.