50-Foot Radius Concrete Water Tank Foundation in Milpitas
When you drive up into the Milpitas hills, you already know you’re in for a view. From this spot, you can see a big stretch of Silicon Valley, and this is where we built a brand-new 209,000-gallon concrete water tank foundation for the City of Milpitas.
This tank is used primarily for fire protection, so there’s no room for mistakes. Everything about this build had to be clean, structural, and intentional — from shaping the pad to ensuring the foundation could support the full load of a tank this size.
Full Project Photos:
👉https://tinyurl.com/milpitasagriculturalshed
YouTube Video For This Project:
👉 https://bit.ly/50FootWaterTankGradeBeam
Setting Up a Large Circular Foundation on a Milpitas Hillside
Excavation, Grading, and Layout
The first step was carving out a flat, workable pad large enough to handle the tank footprint and all the accessory foundations. Once that was in place, we laser-leveled the entire area so the circular layout would sit dead accurate.
With a foundation this size, especially on a hillside, you can’t start forming a circle until the base is right. Everything that comes after depends on it.
Why a 50-Foot Radius Requires Precision
This isn’t just a circle — it’s a structural water tank foundation supporting over 1.7 million pounds of water when the tank is full. At that scale, every inch matters, and every form board has to land exactly where it’s supposed to.
When you’re working with this kind of weight, there’s no room to cheat the layout. If the circle’s off, everything downstream is off.
Challenges on the Hillside
Between the wind and the slope, we were constantly checking levels and alignment to make sure everything stayed where it needed to be. On a hillside like this, small shifts can turn into big problems if you don’t stay on it.
That said, the view didn’t hurt — standing up here looking out over the city almost makes you forget you’re working.
👉https://tinyurl.com/milpitasagriculturalshed
👉https://tinyurl.com/milpitasagriculturalshed
Formwork and Reinforcement for a True Structural Tank Base
This is where the craftsmanship really shows up. Anyone can pour concrete — not everyone can form and reinforce a true 50 foot-diameter circle that actually holds its shape and stays on layout.
With a tank base like this, the formwork and reinforcement aren’t just about looks. They’re what make the whole system work once the weight is on it.
Curved Form Setup
We built the radius using 2x12s, trimming each board by about 1.5 inches to dial in the exact curve. It took a total of seven 2×12 arcs to wrap the entire ring and keep everything consistent.
That curve looks smooth in photos — but trust me, you earn it. Getting a circle like this right takes time, patience, and constant checking.
Rebar Placement and Spacing
Inside the form, we ran #3 stirrups at 12 inches on center, with (2) #5 rebars at the top and (2) #5 rebars at the bottom to tie everything together.
That’s the kind of reinforcement layout you need when the tank is holding over 200,000 gallons of water. This isn’t about overbuilding — it’s about building it right for the load it has to carry. you need when the tank is holding over 200,000 gallons.
Keeping the Radius Perfectly Round
We used a center-pivot arm to lock in the radius and keep the ring true the entire way around. That’s how you avoid waves, flat spots, and small inconsistencies that turn into big problems once concrete is placed and the weight is on it.
Pour Day — Placing and Finishing the Concrete Ring
Pour days on hillsides are always a mix of timing, communication, and just straight hustle. Everything has to move in sync, especially when you’re placing a continuous circular pour like this.
Concrete Delivery and Access
The trucks had to make a tight climb up the hill, so staging and timing mattered. Once they were in position, we kept the mud moving to make sure the ring placed and set up evenly all the way around.
Vibration, Leveling, and Finishing
Every section was vibrated, the finish was tied in, and elevation was checked continuously as we worked around the perimeter. A foundation this size can’t afford dips, waves, or high spots — everything has to land where it’s supposed to.
Curing and Final Inspection
After the pour, we came back to strip the forms, clean up the site, and make sure the entire ring was properly cured. What you see now is a clean, even, structural concrete tank pad, ready for tank installation.
Additional Tank Pads and Utility Foundations
This site included more than just the main tank ring. We also formed and poured three additional tank accessory pads that sit in front of the primary foundation and tie directly into the overall system.
Each pad had to be laid out, reinforced, and poured with the same attention to alignment and elevation, even though they’re smaller. On a site like this, everything has to work together once the tank and utilities are in place.
Layout, Forming, and Pour Sequence
Each pad had its own reinforcement, alignment, and elevation checks. Even though they’re smaller than the main ring, they still had to be tied in cleanly and function as part of the overall tank foundation system.
How Everything Works Together
Once the tank is assembled, all four pads function as a complete system — supporting access, utilities, overflow, and ongoing maintenance. Everything must align so the site works as intended long after the tank is online.
The Views Don’t Hurt Either
The Views Don’t Hurt Either
The Milpitas hills give you that backdrop where you can see the entire valley — San Jose, the back side of Fremont, and the freeways winding through below. It’s the kind of scenery that makes the long days worth it.
You’ll see it in the drone shots — open hillside, blue skies, and a **clean concrete pad
What We See in the Field vs. What’s on Paper
Plans always give you the clean version — straight lines, perfect curves, zero surprises. But out here in the Milpitas hills, the ground tells its own story. Every cut, every grade adjustment, and every form we set must respond to what the site actually provides.
The engineer provides the design. We bring it to life in the field.
On a project like this — a 209,000-gallon water tank, tight hillside access, and a curve you can’t cheat — communication with the client and inspectors is everything. Adjustments happen. What matters is keeping everyone informed and ensuring the final foundation performs as intended.
Most people only see the finished foundation. They don’t see the conversations, the layout checks, or the back-and-forth that make everything line up. That’s the part we take seriously. We stay ahead of the details so the client doesn’t have to. By the time we’re done, the tank installers can roll in and get to work with confidence.
Schedule online ⏩
https://tinyurl.com/AllAccessEstimates
Call/text: 510-804-4646
