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The original item was published from 6/18/2018 2:06:52 PM to 7/19/2018 12:00:00 AM.

News Flash

City Manager's Office

Posted on: June 18, 2018

[ARCHIVED] Townwide Drainage and the Water Detention Facility


In 2015 the Town completed its Town-wide Drainage Study Update. In addition to identification of drainage improvements throughout Town, that Study specifically identified a need to reduce flooding associated with the Atherton Channel through the use of a stormwater detention facility. These “open field” detention basins are conceptually designed to take overflow from the Channel and “flood” the open fields on each site to about 4.25 feet in depth. Construction of adequately sized “open field” detention basins at Las Lomitas Elementary School and Holbrook Palmer Park to address a 10-year storm event was estimated at $4 to $6 million. Other drainage needs identified in the Study dealt with various swales along the Town’s roadways, erosion control projects, and culvert repairs. These drainage improvement projects were prioritized from Tier 1 to Tier 5, with Tier 1 being the most critical, at a total cost of $41.4 million (in 2015). These drainage infrastructure needs were prioritized out over the next 15 to 20 years of capital improvement programming for the Town, as funding became available.

HPP Field BasinThe needs identified in the Study and the new State-mandated requirement for each jurisdiction to reduce mercury and polychlorinated biphenyl (PCB) levels being discharged into the Bay via active or passive water treatment projects (including “green infrastructure”) prompted the Town to search for solutions – both financially and in partnership.

Channel DistrictThe Town comprises about 51% of the Atherton Channel watershed. Portions of the Town of Woodside, City of Menlo Park, and unincorporated Stanford lands also drain into the Atherton Channel before those waters leave Town at the Marsh Road Culvert. The Town formed the Atherton Channel Drainage District in 1958 and it exists today as a separate legal entity from the Town itself but governed by the City Council as its governing board. The District covers approximately 6 square miles and includes property in and outside of Town. Properties within the District, to include those outside of Town, pay a portion of their property taxes to the Town specifically for drainage projects within the Channel District. The Town receives approximately $100,000 a year in property taxes from properties in the District – Atherton, Menlo Park, Woodside, and the County. Through the property tax allocation, properties that drain into the Channel pay to maintain the Channel. However, as noted above, there are a significant amount of drainage improvement projects that must be completed, and the cost of these projects far exceed the current level of property tax collection from properties in the District. The Local Agency Formation Commission (LAFCO) conducted a Municipal Services & Sphere of Influence Review of the Town and District in 2008 and identified that the District receives insufficient funds to repair and/or replace portions of the now 45-50-year-old channel. LAFCO advised that capital improvements for the channel have been financed on a “pay as you go” basis and based on annual revenue, projects will be limited unless a new revenue source, such as a special assessment, is identified.


Water Detention Project

As mentioned above, the Study identified three possible sites for the detention facility including Las Lomitas Elementary School, Holbrook-Palmer Park, and the Menlo Park Circus Club (JL Dixon Stables).  Due to the complexity of working with a privately-owned site at some distance from the Channel, the Town chose not to pursue a location at the Menlo Circus Club. The Town next attempted to work with the Las Lomitas Elementary School District on a water detention project at the School. This opportunity ultimately proved unsuccessful after the Town and District were unable to come to agreement on funding, approval of a traffic signal at Walsh Road, continued maintenance, the Town’s ability to terminate the project prior to construction, if desired, and long-term financial obligations (lease/easement).

Las Lomitas Field BasinInitial discussions with Las Lomitas Elementary School District were based on the “open field” design for the project that was identified in the Study with a Town cost of $3-$4 million. Subsequently, the Town learned of a collaborative funding opportunity with Caltrans to not only provide the Town with the needed flood control project; but also, an opportunity to address the Town’s State-mandated requirements under the Regional Water Quality Control Permit. The Caltrans collaborative project provides the Town with up to $13.6 million for the study, design and construction of a water detention project. Caltrans is required to address its runoff from state lands and highways. Because a portion of the state highway system finds its way into the Atherton Channel, the project provides a benefit to Caltrans.

After being selected by Caltrans for the Project, the Town hired Tetra Tech Inc. to investigate the feasibility of installing a water detention facility at the School under their newly proposed parking lot. However, when discussions with the District proved unsuccessful, the remaining location to investigate for feasibility was Holbrook-Palmer Park. Caltrans authorized the Town to shift focus from the School District property to the Park and conduct another feasibility analysis.

Upon direction from the Town, Tetra Tech Inc. began conducting a feasibility and concept plan for a water detention facility at Holbrook Palmer Park. Funding for consultant work and all staff time related to investigation of a water detention project, regardless of its location in Town, is paid for under the Caltrans Cooperative Agreement. Funding under the Cooperative Agreement comes in phases and the Town is required to expend $5.5 million on the project by May 2019 or risk the loss of this portion of the $13.6 million. However, prior to selection and acceptance of a 20% design project, the Town can exit the Cooperative Agreement without commitment to construction of a project.

The prospect of a water detention project at Holbrook Palmer Park was reviewed by the City Council and Parks and Recreation Committee at various public meetings with the last occurring in May 2018. Following these meetings, the Council opined that placement of a facility at the Park, while conceptually feasible, is not an option they would like to decide upon at this time. The Council directed that staff evaluate the possibility of a project at an alternative location in Town.

Following that direction, staff re-examined the possibility of a facility at Las Lomitas Elementary School, the feasibility of a facility at Menlo Park Circus Club and the possibility of a facility near Menlo College and Menlo School along El Camino Real that could capture water from the Channel as well as areas of poor drainage along El Camino Real at Selby, Stockbridge, Almendral, and Tuscaloosa.

Because these alternative locations involve facilities on private property, the Town must first adopt an ordinance that will allow it to negotiate a public-private collaborative agreement for public use of private property – a development agreement ordinance. A draft development agreement ordinance will be presented to the City Council at their July 18 Regular City Council Meeting for introduction. If introduced, the ordinance would return for 2nd reading and adoption in September and, if adopted, would be effective in mid-October. During this period of time, staff will be connecting with possible site owners to discuss the site(s) as opportunities for a water detention facility. The ordinance itself is non-project specific as the ordinance is solely the underlying authority for the Town to enter into development agreements.

If a site is selected as an opportunity, the City Council would enter into a development agreement with the property owner and begin site exploration for the project to develop a feasibility analysis and ultimately a 20% Concept Plan. As a project under the California Environmental Quality Act, any potential project would be required to go through the environmental review process as well as a separate public process for review and approval, if selected.


Staff anticipates returning a development agreement for a public-private collaborative project location to the City Council for consideration sometime in October/November 2018 and a feasibility analysis sometime in November/December 2018.

Thanks for reading!

George Rodericks

City Manager

Town of Atherton

(650) 752-0504


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