Hacienda and Deep Gulch Calcines Remediation Project
In October 2022, the Parks Department will begin implementation of the Hacienda and Deep Gulch Calcines Remediation Project near the Hacienda entrance to Almaden Quicksilver (AQ) County Park. This project is the next in a series of remediation efforts undertaken since the early 1990s by the County Parks and Recreation Department to mitigate environmental impacts of calcine material through removal and/or stabilization of visible calcines in the park.
Almaden Quicksilver County Park was once the site of extensive quicksilver (mercury) mining spanning over 135 years. The calcine material (rocks and sediment) is the biproduct of this former mining activity. Over time, exposed calcines in the park may become mobilized during storm events and transported through the Guadalupe River system and into San Francisco Bay where the mercury in the calcines may be converted into methyl mercury by naturally occurring bacteria and absorbed by aquatic plants and fish.
The primary goal of past and current remediation projects is to reduce the risk of calcine material entering the creek system where it can negatively impact biological resources over time. The Hacienda and Deep Gulch Remediation Project will provide a long-term sustainable creek system within this area of AQ County Park with a reduced risk of calcine impacts to fish and other wildlife.
The remediation work is mandated by the legal framework of a Consent Decree signed in 2005 by Santa Clara County with the United States Fish and Wildlife Service (USFWS) and the California Department of Fish and Wildlife (CDFW).
The current remediation project will commence with initial tree removal activities in October 2022 to remove selected trees within the remediation area and continue in Spring 2023 with implementation of calcine removal and stabilization activities, slope stability improvements and habitat enhancement and restoration.
Fall 2022 Tree Removal Phase of Work
Much of the calcine material to be removed in the spring of 2023 is located on heavily vegetated, steep banks and slopes above Alamitos Creek and Deep Gulch. Trees growing on calcine material must be removed before the calcines can be removed since the calcine material is intermingled throughout the soil and root systems of the trees.
The County is removing many of the trees in the Fall of 2022 to limit the potential impact on nesting birds and roosting bats in the upcoming season. Only trees outside of the creek flow area can be removed in the fall. Trees within the creek flow areas will be removed during the next phase of work commencing in the Spring of 2023
The overall project has focused heavily on preservation of the natural and historic resources within the project area. During
design, the footprint of the original calcine removal was re-evaluated to further reduce the disturbance and impacts to trees and habitat. As a result, Parks was able to preserve several large 100+ year old Valley Oaks and other trees and minimize disturbance of adjacent habitats. In addition, enhanced habitat features were incorporated into the project design to provide additional benefit to endangered species such as steelhead trout.
The total number of trees being removed is 140, with over 30% of these trees less than 6 inches in diameter, and 15% over 24 inches in diameter. All trees removed will be mitigated (replaced) as required by the California Department of Fish and Wildlife under a Lake and Streambed Alternation Agreement.
For additional information on the Hacienda and Deep Gulch Calcine Remediation project, please contact Alicia Flynn, Project Manager, at (408) 355-2209.