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Biotreatment Soil Mix Benefits for the Bay Area

Landscaping|Organic / Sustainable Landscaping|Landscape Materials

Introduction

Biotreatment Soil Mix (BSM) offers a range of benefits that go far beyond filtering runoff. It helps protect local water bodies by minimizing pollutants, promotes healthier growth for plants and trees, and contributes to creating vibrant, sustainable, and resilient landscapes. A well-chosen BSM also supports diverse ecosystems, offering essential habitats for wildlife and bolstering overall ecological health. At Lyngso, we recognize the growing interest in Biotreatment Soil Mix—and the questions that often come with it. In this article, we’ll explore the key advantages of BSM as well as the importance of biotreatment for soils in The Bay Area.

What Is a Biotreatment Soil Mix (BSM)?

A Biotreatment Soil Mix (BSM) is a specially engineered soil mixture designed to maximize water infiltration and remove pollutants in stormwater treatment systems. Typically composed of 60%–70% sand and 30%–40% compost, BSM filters runoff at a rate of 5 to 12 inches per hour. The sand component enhances drainage and infiltration, while the compost helps to retain moisture and capture contaminants. Biotreatment Soil Mix is commonly used in bioretention basins, bioswales, and other green infrastructure applications, providing effective stormwater management while still holding enough moisture to sustain strong, thriving plants.

Photo Credit: Guzzardo Partnership

BASMAA Specifications

Why Meeting BASMAA Specifications for Biotreatment Soil Mix Is Key

The Bay Area Stormwater Management Agencies Association (BASMAA) and its members have identified significant concerns with current BSM specifications. In particular, nutrient leaching has emerged as a pressing issue, with standard mixes contributing to the loss of nitrogen and phosphorus and the flushing of pollutants like copper. These processes exacerbate stormwater runoff pollution, posing a threat to the health of local water bodies, including the San Francisco Bay.

Additionally, poor tree performance in some BSM designs has raised further concerns. Healthy trees are increasingly recognized for their stormwater and ecological benefits, such as enhancing infiltration, reducing runoff, and supporting biodiversity. To address these concerns, BASMAA has proposed key refinements to BSM specifications. For example, reducing compost content to a maximum of 30% aims to lower nitrogen and phosphorus leaching.

Lyngso’s Biotreatment Soil Mix Is Made Per BASSMA Specifications

Our Biotreatment Soil Mix meets both BASMAA and SFPUC specifications, fully complying with the “Soil Specifications” criteria approved by the Executive Officer of the San Francisco Bay Regional Water Quality Control Board on April 18, 2016, under Provision C.3.c.i.(2)(c)(ii) of the Municipal Regional Stormwater Permit (MRP).

Lyngso’s Biotreatment Soil Mix is highly effective at filtering stormwater runoff while supporting thriving vernal and riparian plant communities, whose roots naturally enhance the purification process, contributing to healthier ecosystems.

Photo Credit: BlueRidgeKitties

Biotreatment for Soils in the Bay Area Is Becoming More Important Than Ever

Bay Area’s growing urban and industrial activities generate polluted runoff that affects water quality, public health, and ecosystems. A well-designed Biotreatment Soil Mix (BSM) offers a sustainable solution to tackle this challenge. By using a specially formulated BSM, which optimizes conditions for microbes that break down harmful contaminants, polluted soils can be effectively remediated over time.

Three Key Benefits of Biotreatment Soil Mix

1. Stormwater Management & Improved Water Quality

One of the primary benefits of Biotreatment Soil Mix (BSM) is its ability to filter stormwater runoff. As stormwater flows through the BSM, it undergoes a natural filtration process that removes pollutants. The sandy texture allows water to infiltrate quickly, capturing sediment and preventing it from entering nearby waterways. At the same time, organic compost promotes microbial activity that breaks down contaminants like oils, heavy metals, and organic waste.

This process also reduces excess nutrients, such as nitrogen and phosphorus, which can otherwise lead to harmful algal blooms. The result is cleaner runoff, helping to protect and preserve our local water bodies.

2. Enhanced Plant and Tree Growth

Biotreatment Soil Mix is specially designed to create the perfect environment for healthy root growth. Its high sand content ensures good aeration, preventing water logging that can lead to root rot, while the compost provides essential nutrients for long-term vitality. The organic matter also encourages beneficial microbes that support root health and strengthen the plant’s resistance to disease. This balance of drainage, moisture retention, and microbial activity is essential, as healthy trees play a vital role in stormwater management and ecological health. It is important to select plants that are specified for the Biotreatment/bioretention areas. San Francisco Stormwater Management Requirements and Design Guidelines offer a Low Impact Design (LID) plant list for the Bay Area climate.

Photo Credit: Guzzardo Partnership

3. Broader Ecosystem Benefits

Using Biotreatment Soil Mix in landscapes and urban areas helps create thriving, interconnected ecosystems. By filtering out pollutants it protects aquatic habitats downstream and promotes healthier wildlife populations. Furthermore, the mix’s blend of sand and compost promotes plant diversity and supports various vernal and riparian plant communities, whose roots also help in filtering stormwater runoff and improving overall water quality.

Improved soil structure and aeration also support soil microorganisms that play a key role in nutrient cycling. This healthy soil biology strengthens root systems, prevents erosion, and sustains the balance of local plant and animal life.

Photo Credit: Cal State Fullerton

Final Thoughts

By thoughtfully integrating Biotreatment Soil Mix (BSM) into your landscape or green infrastructure application, you can enhance stormwater management while supporting healthier plants and a more resilient ecosystem. Visit our showroom and landscaping yard in San Carlos for expert advice and inspiration and contact us today to learn about delivery options for your SF Bay area home. For additional Bay Area–specific guidance on biotreatment and stormwater management, check out the comprehensive resources available at FlowToBay.org.

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