The Field

Cool pavement systems as a hot mix asphalt alternative is encouraged by state legislation in California.

The Water Conservation PPN is highlighting two ways cool pavement technology save water.  First, reducing paving temperature reduces water evaporation from soil adjacent to paving. Also, plants in close proximity to pavement lose water quickly, when compared to plants adjacent to cool pavements. In addition to positive air quality impacts (carbon, VOC’s, temperature, etc.), water conservation is a good reason to look at new resin based paving technology. This will be explored here through a case study of a project in Northern California: Lake Merritt located in the middle of Oakland, CA.

Lake Merritt was a saltwater wetland area and originally an estuary of San Francisco Bay. The water body was hunting and fishing grounds for the Ohlone Indians until 1810, when the tribe moved to Mission San Jose. The City of Oakland founded in 1852 made the estuary an open water municipal sewage treatment system until 1869. Dr. Samuel Merritt, Mayor of Oakland, promoted the idea of a separate sewage treatment system and personally funded the construction of a dam to control the water at a higher level with a greater percentage of fresh water content from the surrounding streams. Dr. Merritt succeeded in lobbying the State of California to create Lake Merritt as a state wildlife refuge in 1870, the first known wildlife refuge in North America.

In 2002 a bond measure was passed to improve Lake Merritt, including the water quality of the lake.  The Lake Merritt dam will be demolished to restore natural tidal flows with the San Francisco Bay via the Oakland Estuary. Part of the $198.5 million City of Oakland bond, “Measure DD”, is dedicated to the 3.4 mile multi-use perimeter recreation path around the lake, including cool pavement installation.

Cool pavement path surfacing selected is a flexible pavement material known as the NaturalPAVE® XL Resin Pavement™ featuring a high environmental performance alternative compared to heat absorbent asphalt pavement materials that use carbon based petroleum.  Favorable test comparisons of cool pavement to hot mix asphalt materials shows that the resin pavement product selected for Lake Merritt is cold-manufactured, cold-applied, nontoxic in composition, and typically solar reflective.

The first phases of the Lake Merritt project were completed while current Governor Jerry Brown was Mayor of Oakland.  As Governor, he signed state Assembly Bill AB 296 directing Caltrans agency to speed implementation of cool pavements by developing material and construction specifications to help public agencies expand applications enabling cool pavement materials to be specified.  Nontoxic, high performance, flexible pavements such as SSPCo’s NaturalPAVE directly address urban heat island concerns, counteracting climate change pressures, reducing energy requirements in hot weather cycles, and providing clean reliable pavements on water quality sites.

John Gibbs, ASLA of Wallace Roberts and Todd’s San Francisco office served as landscape architect directing the Master Plan for Lake Merritt, noting: “WRT is a green advocacy firm since the early 1960’s, and many view the 1970’s as the dawn of the environmental movement, yet Lake Merritt’s green story from 1870 inspires us and still continues to unfold”.

For more information on Lake Merritt’s story, please see “Polishing Oakland’s Crown Jewel: Lake Merritt Reborn” by Amy Miller on the online magazine, QUEST.

by Samuel Randolph and Matt Mathes, ASLA, Water Conservation PPN Chair