U.S. Forest Service "Big Pines Rock Reservoir" Project
POLYUREA CASE STUDY: U.S. FOREST SERVICE “BIG PINES ROCK RESERVOIR” LINING REPLACEMENT
By: Jim Sliff, Innovative Painting & Waterproofing, Inc.
Project outline:
Re-coating of interior walls, floor, ceiling and exterior coating of roof of 300,000 gallon rectangular concrete potable water tank, primarily below-grade. All concrete/plaster construction with reinforcing steel and steel beams.
Unique features:
1. On US Forest Service land at Mountain High West ski resort ¼ mile up the main hill of a “feeder” trail leading to the base.
2. Built in 1929, the tank provides both potable water to the resort base and nearby Ranger Station but also water to snow-making equipment.
3. The tank is a historical structure with an historical preservationist supervising the exterior aesthetics; requirements were to match old natural concrete as closely as possible - but with a membrane system.
4. Existing interior plaster skim coat and ceiling/steel coatings were 78 years old – no maintenance coatings work was ever performed after initial construction, nor any patching, nor silt removal. Normal water flow had been maintained, plus approximately 100 gallons per day lost through leaks and evaporation – but the main drain valve had not been opened in 78 years.
Primary Materials used:
- Sonneborn Gel Patch Polymer Concrete Repair Mortar.
- Sherwin-Williams 100% solids Epoxy Primer (several types, as wall conditions changed dramatically as walls were exposed to air, with some double-primed areas) – 200+ gallons
- Sherwin-Williams AR520PW Aromatic Polyurea – 600 gallons
- Assorted Polyurea and Acrylic finishes for faux-concrete finish on roof
- Sonneborn NP-1 Urethane sealant
Primary material supplier: Sherwin-Williams Company
Repair products supplier: Sonneborn Division of BASF
Equipment maintenance and support: Diamond Liners Inc., Santa Fe Springs CA
Specialty electrical engineering: Doug Farrell, Brea CA
Project Manager: Jim Rough, US Forest Service
Contractor: Innovative Painting & Waterproofing Inc. – Brea CA
The tank was brought to our attention by the ski resort, which had retained Innovative to do a partial interior polyurea coatings job on a steel tank at Mountain High East to stop some significant leaks. That project, done with Sherwin-Williams AR520PW Polyurea was very successful, and the return-to-service time got the attention of the Forest Service, who desperately needed to solve leak issues with their “Rock Tank” but could not take it out of service for long. A very tight schedule was required due to employment of a portable 4,000 gallon water tank for all users until the “Rock Tank” was back in service – and it HAD to be back in service prior to ski season.
Since the existing condition of the tank was excellent considering its age, a plan was developed to carefully power-wash cementitious surfaces, with metal requiring no hazardous materials containment nor usual preparation – it was in astonishingly good shape. There was no budget for testing or abatement, and encapsulation with a surface tolerant potable water epoxy was the most cost-effective solution acceptable to the Government, Engineers and Safety Directors.
The site was accessible but tricky – front access was possible only with pickup trucks. All equipment had to be brought in on a 2 mile long,unpaved, partially-graded fire road – with the main equipment trailer delivered with some judicious use of shovels to avoid chassis damage and a chain saw for height clearance (load-out was possible using the front slope – very slowly).
As roof areas were patched, molded and prepared, Innovative’s team ofpolyurea specialists immediately followed with an epoxy prime coat,
aromatic polyurea base coat, and an historian-approved mix of polyurea sealant and acrylic coatings in a heavy “spatter-coat” to approximate the look of ¾-century old, exposed-aggregate concrete. This system was critical to the success of the entire infrastructure, as any water penetration through the roof could have caused delamination of the polyurea ceiling coating. The AR520PW Polyurea was applied by high-temperature, high-pressure plural-component spray using Graco EXP-2 Reactor pumps(with feed pumps air compressor and repair/maintenance shop all enclosed in a trailer with the EXP-2) and Fusion guns. A portable generator was used for power as Innovative’s larger, self-contained rigs could not reach the site.
With the quick-set properties of AR520PW, Innovative’s spray technicians were able to immediately follow with the spatter coat in a staged process using 4 different colors (plus the base, a light gray). The result was a startlingly realistic “worn concrete” look that will only improve as the fresh coatings lose their slight sheen.
While interior work was proceeding during completion of the roof, the majority of it was slated to start once the roof was watertight. The two major surprises inside the tank were 1) less than 2” of silt had collected inside, making cleanout relatively easy (offset by the additional surprises…and work…as walls dried out) and 2) the 78-year-old main drain valve opened with only one small crack in the control wheel (and later closed with no problem). That valve was, of course, critical to the whole operation and if it had been frozen an expensive replacement would have been needed – and fast.
One other surprise was in store, though it was partially expected; as the walls dried out, they became more porous and subject to pinholes, requiring extensive double-priming and skim-coating to eliminate the problem.
Despite one shockingly early day of light snow the project finished right on schedule.
The main valve was closed, the tank filled and water loss was no more than normal evaporative calculations. Although the polyurea coatings are not projected to provide 78 years of service, they solved the leak issues and helped prevent a potential battle (and large budget issue) over possible demolition and construction of a new steel tank.
Article re-posted with permission from the Polyurea Development Association: www.pda-online.org