About PHWD


Purissima Hills Water District (PHWD) is a County Special District serving drinking water to approximately 6,400 residents and 10 institutional customers in Los Altos Hills. PHWD water is purchased from the San Francisco Public Utility Commission (SFPUC) which collects and stores rain and snowmelt from the Sierra Nevada Mountains. This source is high quality, soft water. No groundwater is delivered to PHWD.

The District is governed by an elected Board of Directors composed of five members. A General Manager oversees District operations performed by two office staff and four field crew.

In the early 1950s, there were about 350 homes and small ranches in an area west of Los Altos known as Purissima Hills. Some residents had private wells; other residents had organized themselves into small mutual water associations (Stonebrook and Toyon) which distributed water obtained from community wells or, in the case of three such mutual water associations (Purissima, Robleda, and Blanco Rancho), from the California Water Service Company. In 1952, there was a drought in the land and in response to the water shortage, a group of citizens formed the “Purissima Hills Association”. The Association engaged the services of an engineer to study the water situation and to 0prepare a report recommending the means and cost of providing water for area residents. The report, completed in 1953, recommended that the residents form a County Water District and that it purchase water from San Francisco’s Hetch Hetchy system. The District was incorporated on April 26, 1955, and a Board of Directors was installed.

Collage of various PHWD District activities and facilities

The Board retained an engineer to design a water system and began planning for its construction and financing. Plans and specifications for the original water system were prepared and, on August 1, 1956, the District sold $350,000 general obligation bonds to finance construction that was started in August 1956 and completed before the end of the year. The work included two 100,000-gallon redwood tanks—one on Ascencion at an elevation of about 250 feet and one on La Cresta at an elevation of about 450 feet. Water was delivered to the lower tank via pipeline from the Hetch Hetchy pipes near Foothill Expressway and Arastradero Road. Two 25-horsepower pumps lifted the water from the lower tank to the upper tank.

This system served some 50 homes along Fremont, Concepcion, Manuela, Page Mill, and Arastradero Roads. Between 1956 and 1960, many homeowners, and small and large developers dissatisfied by the water quality and/or production of their wells, sought annexation to the District. In 1960, the District constructed the 500,000-gallon Elena tank on Vista del Valle (near Taaffe) to provide additional storage capacity to supply the newly completed Foothill College. The fledgling community college district participated in financing construction of the tank and connecting pipelines.

In the summer of 1961, water shortages were once again in the land. The wells supplying two mutuals (Stonebrook and Toyon) south of Foothill College would no longer allow them to meet the demands of their customers. The District stepped to the breech and provided temporary supply, followed by annexation of the area served by the two mutual companies. Over the next ten years, as the growth in Los Altos Hills’ population exceeded the ability of the remaining three mutual water associations (Purissima, Robleda, and Blanco Rancho) to supply their customers, the District annexed (sequentially) the areas served by them. During this period (1961-1970), the District constructed five tanks adding over three million gallons of storage capacity to the system and installed a second connection to the Hetch Hetchy system pipeline.

Since 1970, the population served by the District has grown from about 3,400 to about 6,400. Two tanks, each having 3.0 million gallons of storage capacity, have been added to the system, and the one million gallon La Cresta tank, constructed in 1962, which failed during the 1989 Loma Prieta earthquake, was replaced with a similarly sized tank in 1992. The District now has eleven tanks and a storage capacity of almost 10 million gallons.

The District takes pride in its history in Los Altos Hills and looks forward to continuing to serve its residents in the years ahead.

Written by Ernie Solomon

District Boundary Map


Purissima Hills Water District is a member of the Santa Clara Local Agency Formation Commission (LAFCO).

Mission of Santa Clara LAFCO

The mission of LAFCO is to promote orderly growth and development in Santa Clara County by:

  • Preserving agricultural lands and open space;
  • Curbing urban sprawl;
  • Encouraging efficient delivery of services;
  • Exploring and facilitating regional opportunities for fiscal sustainability; and
  • Promoting public accountability and transparency of local agencies to improve governance

LAFCO Agency Review 2011 (PDF)

LAFCO Recommendations 2012 (PDF)

Response to LAFCO 2012 (PDF)

Multi-Jurisdictional Local Hazard Mitigation Plan

Purissima Hills Water District is participating in the Multi-Jurisdictional Local Hazard Mitigation Plan (MJ-LHMP) with the Association of Bay Area Governments (ABAG) taking the role of the lead Agency representing all participating Agencies when communicating with the Federal Emergency Management Agency (FEMA) and California Emergency Management Agency (CalEMA). ABAG has received funds not only to coordinate this effort, but to execute the plans final strategy. Participating in the MJ-LHMP will allow Purissima Hills Water District to be eligible for funds (FEMA, CalEMA) pre and post disaster mitigation should the need arise. For example, in the event of an earthquake, the retrofit or replacement of damaged District infrastructure may be required.

Purissima Hills Water District's strategies in draft form (PDF)

California Special Districts

Special Districts are formed under California law for local specialized services and are publicly owned and overseen. For more information, see Districts Make the Difference website or download the PDF here.