The following conversation between Gordon Rose, P.E., and Janet Jackson, GISP, highlights how effective collaboration between civil engineers and GIS professionals can save time and money on complex site-selection investigations, and better serve clients’ needs.

Rose: I need your help. I have a meeting with a client next week. He wants our help finding a site for a proposed development. He needs about 200 acres of land, within one mile of an interstate highway, and supplied by water and sanitary sewer service. Can you help me?

Jackson: Yes, of course I can help. GIS is the perfect tool to help find the solution to your client’s challenge. First, I need to know the state or county in which he wants to locate his new development. My next step is to acquire the necessary base mapping layers. The individual map layers, such as contours, streets, right of ways, rivers, lakes, streams, parcels, et cetera, will be the primary data set that will be used to do the analysis for your client’s specific project criteria.

Rose: That’s great. The client is looking for a site in a well-populated area. And I forgot to tell you that he also needs rail service. I know that this particular area has a lot of wetlands and some poor soils, so we need to avoid those if we can. The poor soils would be those classified as GC, SC, CL, ML, OL, CH, MH, OH, and PT. What is our next step?

Jackson: Checking our company data library to see what data (in GIS format) we have available is my next step. If we have the county data, I will carefully read the accompanying metadata (data about the data) to find out how recently it was created and by whom. If I find that it is older than three years, I will call the county’s land records office to get copies of the most recent GIS base mapping layers. I will be sure to ask for the wetlands, railroads, soils, and the other data layers that I mentioned to you before.

Once the latest data is loaded into our GIS software, I will prepare a general question, or query statement, for the GIS to answer. Using the “select by location” tool and asking a series of sequential questions starts the analysis process. My first query will ask the GIS to select all the parcels of land that are at least 200 acres in size (with the same owner), are within two miles of an interstate highway, are within one mile of railroad access, have access to water and sewer services within 200 feet of the selected parcel boundary, and that avoid poor soils.

Once I have that selected set (for all your specific criteria) displayed, I will print a map of the results. Depending on the results from the queries, we may decide to change the search criteria so that additional “what-if” scenarios are generated. That would be the perfect time to share the initial findings with your client, as his input for further choices and clarification can help guide this process.

Rose: That helps a lot. But I am going to need more than just a map. This is going to be a large user of water, so I will need more information about the water system. The county’s public utilities department has completed a model of its water system that should show us pressures and flows at various locations throughout the county. Can we somehow plug into that model so that I can check water availability at all of these sites you find? I will need at least 500 gallons per minute at 70 pounds per square inch.

Jackson: Usually, model data is kept separate from existing GIS water layer data so that all the “what-if” scenarios modelers use won’t change the underlying GIS water base map information. However, I can input the specific pressure and flow data at water node points (as related attributes) and then ask the GIS to display where the pressures and flows are within the acceptable range, based on your guidance.

Rose: I think we have a solid plan. My engineering staff could have pulled all of this together, but it would have taken them weeks to compile it. It looks like the analysis you can do through GIS will save us time, will save our client time and money, and will help him make good decisions on where to locate his development. Thanks for your help!

Gordon Rose, P.E., senior project manager at McKim & Creed, has 30 years’ experience in water distribution, wastewater collection and treatment, stormwater management, and planning. Janet Jackson, GISP, heads McKim & Creed’s GIS activities company-wide. Contact Rose and Jackson at intersect@mckimcreed.com. McKim & Creed is an engineering, surveying, and planning firm.