Welcome to Menlo Park
As you walk through this innovative parking area, take a moment to notice the ground beneath your feet. Unlike typical pavement, this lot uses special permeable concrete and landscaped biofilters to help protect the nearby San Francisquito Creek. This EarthCache will guide you in discovering how human engineering can work with natural processes to reduce pollution and erosion, all while revealing key principles of hydrology, geology, and environmental science.
Note: A full 16 oz bottle of water is required to complete this EarthCache.
The Geoscience Behind Permeable Surfaces
In a natural environment, the ground acts like a sponge, soaking up rainfall and allowing it to slowly filter into the soil. This process recharges groundwater, prevents flooding, and reduces erosion in nearby creeks. However, paved surfaces like typical parking lots disrupt this natural cycle. Rainwater runs off the hard surface, picking up pollutants such as oil, heavy metals, and trash. It then flows into storm drains and directly into waterways like San Francisquito Creek. This sudden surge of polluted water can erode creek banks, disturb habitats, and contribute to the degradation of San Francisco Bay.
This parking lot was designed to reduce that impact using two environmentally friendly features: permeable concrete and biofilters. The permeable concrete used in the 45 parking spaces contains built-in air pockets that allow rainwater to seep through rather than run off. As water moves through the concrete and the gravel layer underneath, pollutants are captured and held in the upper layers of the material. Instead of entering the creek, much of the water trickles into the ground, where it can be naturally filtered. Runoff from other parts of the lot is directed into mulched planting areas called biofilters. These landscaped zones are made of sand, soil, mulch, and native plants. As the water drains through these layers, particles and contaminants are filtered out. Microbes in the soil help break down pollutants like oil or fertilizer, and the plants absorb nutrients that could otherwise harm aquatic ecosystems.
By mimicking the way water moves through natural landscapes, this design helps reduce erosion, manage stormwater, and improve water quality in San Francisquito Creek. It is a working example of how geology, soil science, and environmental engineering can come together to protect local ecosystems.
Why Was This Spot Chosen?
This site was chosen because of its direct connection to San Francisquito Creek, a vital natural waterway that supports a wide range of plant and animal life. In the past, heavy stormwater runoff from surrounding development has caused serious problems in the creek, including erosion of the banks, flooding, and pollution. When rainwater rushed off paved surfaces like roads and parking lots, it often carried oil, trash, and other contaminants straight into the creek. These sudden surges of polluted water not only damaged habitats but also made it harder for native species like steelhead trout to survive. San Francisquito Creek plays a key role in the local ecosystem. It provides habitat for birds, fish, and other wildlife, and it helps recharge groundwater that supports nearby trees and plants. The creek also flows into San Francisco Bay, meaning whatever affects the creek can also impact the health of the larger watershed.
By building this parking lot with permeable surfaces and biofilters, the creek is being protected from further harm. The design slows down runoff, filters out pollutants, and mimics the natural flow of water through soil and plants. This spot is a demonstration of how thoughtful design can help heal past damage and protect a critical natural resource for the future.
Tasks for This EarthCache
To log this EarthCache, visit the location and complete the following tasks. Send your answers via Geocaching or email.
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Include “Permeable Parking - Menlo Park - GCB98A6” on the first line of your message.
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What differences do you notice between the permeable concrete and traditional asphalt? Describe the appearance and texture of each. Why might the permeable material be better for this location?
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Using your 16 oz bottle of water, carefully pour a small amount of water on the permeable concrete. What happens to the water? Compare this to what you'd expect on regular pavement.
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Examine one of the landscaped planting beds. What materials do you observe? Why are these features important for filtering runoff?
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Based on the information provided, list two environmental problems this parking lot helps reduce and explain how the design helps prevent each one.
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In your log, attach a photo of your 16 oz bottle of water with the Creek-Friendly Parking Lot sign in the background. (Note: photos predating the publication of this EarthCache are not accepted.)