Structure Type: built works - infrastructure

Designers: Daniel, Mann, Johnson and Mendenhall (DMJM) (firm); Phillip James Daniel (architect); S. Kenneth Johnson (architect); Anthony John Hale Lumsden (architect); Arthur Edwin Mann (architect); Irvan F. Mendenhall (civil engineer/structural engineer)

Dates: constructed 1985

2 stories

6100 Woodley Avenue
Van Nuys, Los Angeles, CA 91406

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The Tillman Water Reclamation Plant was a highly innovative technical effort at creating a plant to recycle waste water into potable water. It was surrounded by a picturesque Japanese garden that transformed a utilitarian water treatment facility into a public landmark and park for more general use. Architect Anthony Lumsden (1928-2011) designed the plant for the Los Angeles architectural firm of Daniel, Mann, Johnson and Mendenhall (DMJM).

Building History

This wastewater treatment facility was originally designed to treat 40 million gallons of wastewater per day. It served the district of the San Fernando Valley between the cities of Chatsworth on the north and Van Nuys to the south, comprising about 800,000 people. The City of Los Angeles named the plant for Donald C. Tillman, its City Engineer from 1972 until 1982. The first phase of the plant was completed in 1984 A second phase was finished in 1991.

The plant was planned to operate amidst a Japanese Garden. The City of Los Angeles described this amenity: "The six-and-a-half-acre garden was designed by world-famous designer Dr. Koichi Kawara [sic] and dedicated in 1984. The garden is irrigated with effluent from Tillman, and the 2.75 acre lake is filled with the plant's treated water. The Mayor of Los Angeles appoints members of the Japanese Garden Mayor's Citizens Advisory Committee to oversee all major decisions related to use, maintenance and future plans of the Garden. More than 1,000 visitors come to the Gardens each month." (See City of Los Angeles, Sanitation Department, "Donald C. Tillman Water Reclamation Plant," accessed 05/10/2017.) Koichi Kawana (1930-1990) designed Japanese gardens across the US, including several in Southern CA. Some of these were the Japanese Friendship Garden in San Diego's Balboa Park, the Tillman Garden and work at the Hannah Carter Japanese Garden at the University of California, Los Angeles (UCLA), which was sold in 2016 to a developer.

Building Notes

A City of Los Angeles web site described the plant's process of cleaning wastewater: "The influent pumping facility includes four eight foot diameter enclosed screw pumps which lift sewage into the plant for the initial stages of grit, sand, and trash removal. Barminutors consisting of screens collect the coarse debris and grinders move up and down over the screens, as needed, to shred the coarse material.

Following this preliminary treatment, the wastewater flow into the primary sedimentation tanks where gravity is used to settle most of the heavy particles. A pair of continuous chains connected to wooden scrapers (flights) move settled material (primary sludge) along the bottom to a hopper for disposal to the main sewer line for treatment at the Hyperion Treatment Plant. Floatable material is skimmed off the top by the same flights and also removed to the sewer line for transport to Hyperion.

The next step is the secondary treatment process which takes place in aeration tanks. Compressed air is bubbled through thousands of ceramic domes located on the bottom of the tanks. In this biological process air provides the mixing and oxygen for particles teeming with bacteria, fungi and protozoa. These particles (what is called activated sludge) consume the organic material (pollutional load) in the wastewater, converting it to carbon dioxide, water, and new cells.

Since the activated sludge serves to remove pollutants from the wastewater, it must be maintained at a necessary concentration level. The water containing the activated sludge moves to a final settling tank so that it can settle to the bottom – excess is removed to the main sewer line and sent to Hyperion while the amount necessary for the bacterial process in the aeration tank is returned to that tank. The effluent produced in this biological process flows into rapid mix basin where coagulant chemicals are added to improve the filtration process, the next step in wastewater reclamation.

The filtration process removes a large portion of whatever suspended solids and turbidity are left through continuous backwash sand filters. This material is also returned to the sewer for treatment at Hyperion. Immediately following filtration, chlorine is added to the filtered wastewater, to provide disinfection. At the completion of the process, taking about a total of 11.5 hours, reclaimed water can be made available for reuse, with any excess being discharged to the Los Angeles River." (See City of Los Angeles, "Suiho-En," accessed 05/10/2017.)

Tel:818.756.8176 (2017)


A second phase of construction at the Tillman Plant concluded in 1991. The Los Angeles Department of Sanitation has said of this addition:"A major construction project that doubled the capacity of DCTWRP was completed in 1991, expanding the plant from 40 million gallons of water per day (MGD) to 80 MGD. The Donald C. Tillman Water Reclamation Plant and the Los Angeles-Glendale Water Reclamation Plant (LAG) are the leading producers of reclaimed water in the San Fernando Valley." (See City of Los Angeles, Sanitation Department, "Donald C. Tillman Water Reclamation Plant," accessed 05/10/2017.)

In 2012, the city proposed the removal of a trailer used by Japanese garden docents with a much larger building housing Tillman plant personnel and volunteers. A notice on the web site of the City of Los Angeles Department of Engineering stated in 2012: "The proposed project involves the replacement of an existing 1,250 square foot temporary trailer structure used by Donald C. Tillman Water Reclamation Plant Japanese Garden staff, docents and gift shop with a permanent 17,892 square-foot personnel and multi-use facility building. The building would house the existing employees, docents and the gift shop as well as include meeting and conference rooms and exhibit space. Exhibits currently housed within the Administration Building would be relocated to the new Personnel and Multi-Use Facility building. Following completion of construction the remaining undeveloped portion of the parking lot would be reconfigured to accommodate approximately 113 vehicles. Although the proposed project could result in a significant effect on biological resources, there would not be a significant effect as a result of implementation of the identified mitigation measure." (See City of Los Angeles Department of Engineering, "Donald C. Tillman Water Reclamation Plant Personnel And Multi-Use Facility Project," accessed 05/10/2017.)

PCAD id: 21224