Part 1. Unique pump station building designs.
By Ed Butts, PE, CPI
I announced last year I would author columns from time to time outlining some of my past projects, some successful and unique, some not so much.
This month, as a Christmas present to you, I will kick off this new series with an overview of some unique projects I was a part of. I refer to these as a few of my “pet projects” as I enjoyed designing and constructing them and they accomplished their intended objectives.
I will mention other projects in future columns as some of my “peril projects” as they had difficulties or not as successful outcomes. But this first column has some of the enjoyable ones and includes a few with a common theme: unique building designs. So, let’s get started!
Unique Pump Station Building Designs
A significant portion of my engineering career has included the design of structures for water well, booster, and storm/wastewater pumping systems and treatment of each category.
Although most of the structures involved conventional building construction using common elements such as cement masonry units, wood frame, tilt-up concrete, or steel (metal) buildings, a few involved more unconventional styles, methods, or materials due to their location or application.
Utility structures (i.e., water and wastewater pumping stations and treatment plants) do not always need to look strictly utilitarian. Style and unique architecture can be implemented in many cases, especially when the structures are situated in residential neighborhoods or other sensitive areas.
I have had to employ various design skills so that the finished structure was more than a square or rectangular box, but one that would blend in with the surrounding neighborhood or fulfill a unique design objective. Fittingly, the first examples of these past projects include four water well or booster pumping stations with unique types or methods of building construction.
City of Keizer Lacey Court Well Pump Station
This structure required the inclusion of a facility within a predominantly residential neighborhood. The site included a 12-inch-diameter well drilled for the City of Salem, Oregon, as a test well in an undeveloped area abutting an agricultural field and surrounded by farmland.
The well was originally drilled in 1989 to determine the potential of developing a wellfield to obtain a greater total production. And although the well produced 500 GPM, the results were deemed unfavorable for developing a wellfield.
The well remained unused for several years on an empty lot while a new residential housing development was built around the site. Eventually, the well and lot was residing at the end of a paved cul-de-sac called Lacey Court with new homes on each side.
The City of Keizer, Oregon, finally assumed ownership of the well and lot in 2012. Although the site was procured with the intent to develop the well strictly as a public water supply well facility, the City of Keizer recognized that construction of a typical pumphouse structure would detract from the neighborhood’s appearance, create ill feelings with the immediate neighbors, and potentially expose the site to increased vandalism and trespass due to a generally unoccupied structure.
The decision was thus made to construct a structure with the exterior appearance of a residential home but with strictly utility functions within the interior. The pumphouse is a conventional wood framed structure with T1-11 plywood siding and shingled roof. The doors and windows on the front complete the appearance of a residential home with a few modifications.
The windows use polycarbonate plastic, resistant to small caliber bullets and projectiles, with louvers placed behind the windows. A 1-inch-thick plywood backing board was placed behind the louvers as an additional margin of protection from entry and to lower heating costs.
Entry into the building is restricted to industrial doors on the non-viewable rear side and an 8-foot by 8-foot garage door on the front. The front door is deadbolt locked from the interior and used as a means of exiting only.
The well and four 48-inch-diameter filter vessels were situated in the quasi-garage area to provide adequate horizontal and vertical clear space. A removable cupola with a weathervane was placed over the well to allow removal of the well pump and well maintenance, plus add a touch of class to the building’s appearance.
The site was grassed and provided with an automatic irrigation system to maintain the appearance of a residential lawn. The entire perimeter of the site is protected by a chain link fence with a single-entry gate.
Figure 1 shows the front view of the pump station building and Figure 2 the rear view. Figure 3 shows a view of the well and discharge piping next to the adjacent open garage door.
City of Aurora Well No. 5 Pump Station
The well pumping facility for the City of Aurora, Oregon, was constructed a few years before the Keizer Lacey Court building. The rationale behind the use of residential construction for the Aurora building is identical to Lacey Court in that the facility was designed to blend into the neighborhood surrounding it.
As opposed to the Lacey Court structure, which featured mainly a residential style of wood frame construction, the Well No. 5 building for Aurora is situated in a more upscale neighborhood with brick facades, front entry porches, and vaulted ceilings and roofs.
The building is primarily used to house the electrical and chlorination equipment. In this case, rather than placing the well inside the structure, it was placed behind it and protected within a concrete section to provide greater access to the well and well pump. Figure 4 provides a frontal view of the just completed structure, while Figure 5 illustrates the rear view of the building with the nearby concrete well cover.
City of Monmouth Well No. 2 Pump Station
The elevated structure for the City of Monmouth’s Well No. 2, illustrated in Figure 6, was conceived to elevate the wellhead above the local 100-year floodplain on a tight site.
Typically, I opt to elevate the structure using a structural berm comprised of rock and other fill materials. In this case, however, there was insufficient land area available on the site to build the berm with the needed slopes to the height of 10 feet. This structure, known locally as the “building on stilts,” was constructed in 2007 and uses the well casing as one of the support legs, with the other two legs built from structural steel pipes supported from concrete footings.
The design of the structure was unique as the structure had to be able to withstand not just the imposed vertical soil load but had to resist the possible wind and earthquake loads placed against it. Due to the leverage applied from the 10-foot height, the wind and potential earthquake loads could place a great deal of stress onto the support legs and well casing.
Additionally, the “dead” weight of the structure itself had to be added to the possible 30 pounds per square foot of snow load applied to the roof as a vertical load.
During design, we used a computer modeling program to analyze the various horizontal and vertical loads. The model (Figure 7) provided the various stresses in the structural members that enabled selection of the support legs and building elements.
To prevent any excessive or undue stress to the well casing, the casing was affixed with a ¾-inch by 36-inch circular support plate welded to the well casing and then embedded in a concrete pad that also served to distribute the stresses to a larger bearing area of soil.
The pump discharges water using a welded pitless adapter below grade with the electrical switchgear and wellhead accessible within the structure. Access is provided using a sloped stairway from the ground.
Since this facility was built, I have used this same concept on several other irrigation and public water pumping stations situated within a floodplain, although without the building. And although this facility will likely not win any awards for aesthetics, the final product provides the city with a functional and accessible pump station on a site with limited space.
Pacific City Water District—Henderson Heights Booster Pump Station
The final example is a structure built for the Pacific City Water District as a booster pump station. The district resides in a central Oregon coastal community with soil conditions usually aggressive to wooden structures and the local presence of termites and burrowing animals.
Although constructing the structure using cement masonry units (CMU) exclusively was initially considered, the client expressed a concern with the aesthetics of a CMU structure and blending into a residential neighborhood that consisted solely of wood frame structures.
In addition, the extra weight applied to the soil with an entire CMU structure would have exceeded the safe bearing value of the clay, silt, and sand blend. Finally, the structure also had to be designed to withstand the typical wind and storm events and potential earthquakes from the nearby Cascadia Subduction Zone on the Oregon coast.
A compromise was reached by deciding to use CMU blocks from a concrete slab at ground level to approximately 50% of the height with a conventional wood frame structure comprising the remaining 50% of height (Figure 8).
To lower the overall weight, the roof was a built-up roof using lightweight wood rafter members and steel panels, as there is no ceiling. The booster pumps consist of two 25 HP canned submersible pumps that each operate at a design condition of 250 GPM at 300 feet of total dynamic head. Access to the canned pumps for service is accommodated through roof hatches over each can and a set of double doors on the end of the building (Figure 9).
The client and neighbors were pleased with the aesthetics and appearance of the final structure. The facility was constructed during the mid-1990s and has withstood numerous coastal storms and has functioned well since then with no appreciable decay, destruction, or loss of the building materials.
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Rather than always using vanilla building design concepts, water system designers should consider alternative styles and methods when they are needed to fit the application. I have found many clients to be receptive to this and often appreciate your ability to think outside of the box.
To all readers, I wish to you a happy and safe holiday season. We will return in 2023 with more columns and new topics, so until then, good luck and please work safe and smart.
Ed Butts, PE, CPI, is the chief engineer at 4B Engineering & Consulting, Salem, Oregon. He has more than 40 years of experience in the water well business, specializing in engineering and business management. He can be reached at epbpe@juno.com.