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Hydraulic Simulations

Posted by Murat Ulasir on 7 Apr, 2014
Category: No category

CAC members,
Attached is a hydraulic model matrix we had discussed at the last CAC meeting. Based on the discussions surrounding the topic of hydraulic simulations at our last meeting, our recommendation would be to show you modeling results associated with the simulations shown in this matrix. The modeling results will be based on what we referred to as the "backbone" model (if you will remember, the backbone model includes sanitary sewers larger than 12-inches in diameter). In addition, we are preparing to show you a neighborhood level simulation for one of these simulation scenarios, which is highlighted with a red box in the attached matrix (it is the 50 year return frequency simulation that includes climate impacts). As per our last meeting, my understanding is that the goal of you seeing these simulation results would be to help you

a) get a quick sense for how the system behaves under different conditions (there are three): flow frequency, future growth, and climate impact
b) help you decide which combination of the above stated three conditions you would like to see used in a final, neighborhood level model simulation. This last simulation would then be used as the model to perform alternative evaluations on (please remember that it takes quite a long time to perform a neighborhood level simulation and that is why we had collectively agreed that you review backbone simulations before deciding on the final conditions for developing the final model that can be used for evaluating alternatives).

For the sake of completeness and keeping all hydraulic simulations discussions contained in a single thread (for you to easier follow and search the thread), below, I tried capturing two additional requests by CAC members:


Thank you

Comments

Judy Hanway on 10 Apr, 2014:

Murat and Robert,

I'm confused. What are you asking of us at this time? Are we going to see a report and map for each of the 3 conditions you mentioned (flow frequency, future growth, and climate change) for just the "backbone" model (the larger pipes)? Or will we also see a neighborhood simulation at this upcoming meeting? Will the additional conditions you mentioned (historic SSOs and Township flows) be included in both these models? What neighborhood is being chosen for the simulation and will the citizens on the CAC have input on this decision?

Are you also asking us to choose at this point which conditions to consider in the final report? Do you expect us to make this decision at the next CAC meeting?

Thanks.

Kathy Boris on 10 Apr, 2014:

Judy—Good questions. Thank you for putting them into words.
kb

Murat Ulasir on 10 Apr, 2014:

Sorry for the confusion. Let's try to provide answers to your questions (not necessarily in the order you asked) in hopes that they will clear up some of the uncertainty:

  • are we going to see a report and map for just the "backbone" modelwe are not going to be reviewing or distributing a report; however, we will be reviewing maps of the "backbone" modeling results for the three conditions mentioned (flow frequency, future growth, climate change)
  • will we see a neighborhood simulation at this upcoming meeting?yes, we plan to review neighborhood simulation results for only one combination of the three conditions (frequency, growth, climate) as shown in a red square in the above matrix (my original email) - here's where you CAC members come into play (see next question)
  • what are you asking of us at this time? As it currently stands, we plan to perform the "backbone" (a total of 6) and one neighborhood level simulation identified in the matrix in the very first email I sent out.  As a courtesy to you CAC members (and as part of CAC suggestions from the previous meeting, as I understood it), we wanted to share this intent of ours with you and ask you whether you are OK with this at this time.
  • will the additional conditions be included in both these models? at this time, the "backbone" models will include Twp contract flows in the future growth simulation results, however, they will not be included in the neighborhood simulation results because the proposed neighborhood simulation will include the following condition: 50 year flow frequency + climate impacts. Also, at this time, historic SSO locations will not be included in the maps - we are still working on this and it may take a while to compile this information and map it
  • what neighborhood is chosen for simulation and will CAC provide input on this choice? I see my role as helping CAC understand City system response to flow inputs (i.e. hydraulic simulations) and as such, it is critical for me that CAC provide input. Regarding what neighborhood will be simulated, perhaps I mis-communicated: what I mean by a "neighborhood level simulation" is a simulation that includes the entire City system as it currently exists in the model, i.e. I am not selecting few neighborhoods to simulate but not others...
  • are you asking us to choose at this point which conditions to consider in the final report? no
  • do you expect us to make this decision at the next CAC meeting? it would be great if a decision can be made at the next CAC meeting, based on simulation results we will be discussing...however, if during the CAC meeting you decide collectively that CAC needs more time, I would imagine that request could be forwarded to the CAC meetings facilitator Charlie...

I hope this helps...thank you...

Joe Conen on 15 Apr, 2014:

Sorry that I am a little late to the party on this.
1. It is not clear to me why we would look at the neighborhood simulation without growth but including climate change impacts (C2 @ 50 year). It seems like growth rates and township contracted flows have more certainty than the impact of climate change. Why would this not be the better initial case to build on (i.e C3 at 50 year recurrence)? Or is the neighborhood part of the model insensitive to growth?
2. I am not sure I understand the notes attached to your matrix. For SSO's, is the backbone analysis all that is needed, or is the detailed neighborhood analysis also needed?
Thanks
Joe

Judy Hanway on 16 Apr, 2014:

I agree that the neighborhood simulation should incorporate the impacts from growth.

Peter Houk on 16 Apr, 2014:

How does DOM figure into this though?  Isn't the whole idea of DOM that developers can't build unless they offset their new flow?  

Robert Czachorski on 17 Apr, 2014:

A few comments on the discussion.  We can get into more details tonight.

Existing neighborhood are not really going to experience much growth.  Growth is more likely to affect the interceptors and trunk sewers, so the backbone model runs should give us a good indication of the impacts of growth.  

The idea with the selected neighborhood simulation was to develop a simulation that could represent a good base of comparison between the backbone model and the neighborhood simulation.  There is still some work to do to properly represent the extra flow from growth in the model, so we did not want to run a population growth simulation in the neighborhood model just yet.  We felt that preparing the neighborhood simulation with existing population and no climate change would present a result that was a little too "best case scenario", so we selected the condition of climate change with the existing populations to present as an initial detailed neighborhood model.

Peter is also correct in that the DOM may offset population growth, so that this neighborhood simulation might represent a fairly realistic look at a future scenario with a DOM program continued to offset growth.  That is another reason why we chose the conditions that we did for this neighborhood run. This neighborhood model is a good candidate for a design model, although we are not proposing it as such yet, as described below. 

If the CAC wants to consider DOM as an alternative for the future, the way that we might evaluate that is to perform a model run assuming DOM offsets population growth, and then perform another run assuming that DOM is not implemented, and instead the impacts from growth are handled another way - such as other I&I removal, relief sewers or storage tanks. The CAC can then look at the magnitude of the improvements needed, and the pros and cons of both options, and through applying your community values to the choices, make a recommendation.  This might provide a nice template for how we evaluate a lot of the the decisions. Such a process may require a lot of model runs, and the backbone model is the tool that is capable of making many model runs relatively quickly. 

With all that being said, ultimately, the scenarios that are run and used as the basis for making decisions are up to the CAC.  We presented these as a starting point to get the discussion going tonight on what conditions that CAC would like to see simulated in the model.  It is a fairly significant effort to run the full neighborhood model, so we plan to use the backbone model as a triage tool help the CAC select a scenario for the final design scenario for the full neighborhood model. 

These model results are going to become the central focus of the CAC work and the basis for making decisions and recommendations. This work will span several meetings and will start to become the main thread of finishing the technical work.  The meeting tonight will be a good opportunity to introduce the model, for "tech talk" around the model, how it works, and what simulations make sense to run in the backbone model.  In subsequent meetings, we will focus on input from the CAC on "level of service" discussions, which are driven by flow frequency (i.e. 50 year, 100 year, etc), population growth, and climate change. This will set us up nicely for picking a final "design basis" neighborhood model that we use to identify improvements needed and alternatives. 

I hope this helps.  This starts to provide a road map for how we will wrap up the technical portions of the project.

Take care,
Robert