News and Events

Restoring an Icon: Renovating the Historic Hearst Castle Neptune Pool

posted 06.05.2018

The Hearst Castle in San Simeon, Calif., is a sprawling historic estate comprised of multiple structures featuring 165 rooms, situated on 250,000 acres. The estate was built over many years starting nearly 100 years ago, and the buildings have undergone many changes in that time. To this day, Hearst Castle remains an unfinished project. While the original construction of the Neptune Pool spanned from 1924 to 1936, it has evolved over time. The pool visible today is the third iteration of the original, which grew in size to keep pace with building construction. The unique pool, with its custom Vermont marble tile and iconic Italian statues, and its one-of-a-kind gravity sand filtration and recirculation system created an unusual restoration challenge.

The renovation project was sparked by the discovery of leaks in the pool shell, piping, and filtration system, coupled with a statewide drought. The current owner of the Hearst Castle, California State Parks, enlisted a renowned historical restoration architect Page and Turnbull and renowned aquatics engineer Bill Rowley, Ph.D., to lead the Neptune Pool renovation. Terracon took over the project towards the end of design through the acquisition of Rowley International.

Whether a swimming pool is for public use, recreation, or competition, common issues include maximizing efficiency, conserving energy, and improper design and installation. Terracon has provided environmental, facilities, geotechnical, and materials engineering consulting services for more than 1,000 swimming pool projects across the country.

Construction and New Discoveries

The high potential for unknowns can make an aquatics renovation more complex than new construction, and the Neptune Pool was no exception. Original plans were for only the field white marble tile to be replaced in the interior of the pool shell, while the dark green accent tile was going to be reused as much as possible. However, during pre-demolition testing, natural asbestos was discovered in the existing marble tiles. If the marble tiles could remain fully intact during demolition, then no health hazard would exist. After a test demolition revealed the tiles would break during removal, a full hazardous materials removal of the existing tile was initiated. Total replacement of the tile followed, increasing the construction schedule and budget considerably. The project scope required removing all tile, repairing the concrete shell, installing waterproofing throughout the pool interior, and reinstalling the marble tile finish.


  Another renovation complication occurred during replacement of existing cast iron pool piping in a tunnel.  Several unknown pipes and conduits were discovered and needed to be identified and properly capped. An abandoned electrical conduit penetrating the tunnel ceiling was not capped off and provided an avenue for water intrusion during storms. In the filter area, the project scope included removing all embedded iron pipe fittings, repairing the concrete structure, installing waterproofing on the interior surfaces, and replacing all filter media.  When coring out the ferrous piping fittings, the contractor discovered the existing concrete structure was much thicker than originally anticipated. Terracon developed new repair details to match the existing condition and provide waterproof piping penetrations through the multiple filter vessels.

Creating Creative Solutions

The Neptune Pool project was an evolving engineering problem in need of aquatic design, pool structural, pool electrical, and waterproofing solutions. Terracon’s geotechnical and facilities services were involved on the project.  There are no past projects to review that are exactly like any of the scenarios we encountered. The project team depended on past experience, review of existing conditions, and collaboration with industry experts to provide viable repair solutions to meet the design intent and existing conditions.

For more information on Terracon's aquatics services, visit our Aquatics page.