The permeable stone layer has been prepared for the pervious concrete to be poured.
Rollers are used to compact and level the previous concrete.
The pervious concrete is leveled and tamped down.
Compared to traditional concrete, pervious concrete contains less sand and water and contains more pea gravel. This results in a more porous material with 15-22% void space compared to 3-5% in traditional concrete.
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Pervious Concrete

Pervious concrete allows stormwater to pass through pavement unlike traditional concrete where it runs off into the storm drain system. Below the surface, permeable rock captures pollutants and stores stormwater. Stormwater percolates into the ground and excess flows into the storm drain system through a perforated underdrain.

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Articulated Concrete Blocks

Articulated concrete blocks are a pavement solution for areas with high runoff rates that prevents flooding by providing temporary water storage. The pavers are spaced so that stormwater can enter and accumulate inside the pavers’ arched chambers and in the permeable stone layer below where angular rocks create void spaces. The stored water percolates into the underlying soil or enters the storm drain system through a perforated underdrain.

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The base layer of permeable large angular rock creates void space for water storage.
A layer of medium permeable rock on top of the large angular rock is been tamped down before the articulated concrete blocks are placed.
Geogrid is used to hold the permeable stone in place and prevent it from filling the water storage chambers of the articulated concrete blocks placed above.
Articulated concrete blocks during installation. Integrated drainage spacers allow water to enter in between blocks.
Articulated concrete blocks are placed and leveled. Blocks can be cut to size, e.g. to fit flush against cutoff walls.
Articulated concrete block pavement used for a parking lot.
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A concrete foundation ensures the rainwater tank sits on a solid, flat surface, without risk of tipping over.
Once the tank is placed on the foundation, the pipes and water filter are installed.
Rainwater harvesting tanks typically feature two outlet pipes: one to divert the first flow of water that contains roof sediment away from the tank (“first flush”) and one that acts as an overflow once the tank is full.
Finished installation.
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Rainwater Harvesting

Rain barrels and tanks capture rainwater from rooftops and store it for non-potable uses later, like landscape irrigation. Rainwater harvesting reduces runoff and allows for the beneficial use of rainwater, conserving water. Built-in screens exclude mosquitos from the system.

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Porous Asphalt

Porous asphalt allows stormwater to pass through the pavement, unlike traditional asphalt pavement where it runs off into the storm drain system. Below the surface, permeable layers capture pollutants and store stormwater. Stormwater percolates into the ground, and excess flows into the storm drain system through a perforated underdrain.

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Porous asphalt is poured on top of a layer of medium permeable stone.
Like traditional asphalt, porous asphalt must be tamped down.
Porous asphalt contains fewer fine aggregate particles than traditional asphalt. The remaining large, single-sized aggregate particles leave open voids that give the material its porosity and permeability.
During a rain event, water passes through the porous asphalt shown in front. It does not pass through the traditional asphalt shown in back.
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The pre-manufactured tree well filter is lifted in place, then connected to the underdrain.
The tree well before the sidewalk surface around it is completed.
Finished installation.
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High Flow Rate Tree Well

High flow rate tree wells offer stormwater capture and treatment in locations where space is limited. The tree well filters consist of pre-manufactured concrete boxes filled with proprietary high flow rate media. Stormwater enters through the curb inlet and is filtered by the media and tree roots. Stormwater not used by the tree enters the storm drain system through a perforated underdrain.

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Bioretention Tree Well with Trash Capture

Bioretention tree wells with integrated trash capture provide stormwater collection and treatment where space is limited and pedestrian access needs to be maintained. Stormwater enters through the trash capture inlet where debris is removed before biotreatment soil media in the bioretention area filter out pollutants. Stormwater not used by the tree percolates into the ground or enters the storm drain system through a perforated underdrain. This system was developed by the City of Fremont and is included as a standard detail for construction.

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The distribution pipe carries stormwater from the inlet into the bioretention area.
Pipes must be level to prevent water from backing up.
Porous asphalt contains fewer fine aggregate particles than traditional asphalt. The remaining large, single-sized aggregate particles leave open voids that give the material its porosity and permeability.
A louvered screen keeps trash and plant debris out of the tree well. Access for cleanout is through the grate.
Finished installation.
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Medium permeable stone is tamped down before the structural cells are placed.
Void space between the structural cells is filled half way with Class 2 permeable material.
A layer of biotreatment soil media is placed on top of the Class 2 permeable material.
Geotextile is placed between biotreatment soil media and stone bedding.
Finished installation - front.
Finished installation - back.
Pedestrian access can be maintained above underground structural cells.
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Underground Structural Cells

With underground structural cells, biotreatment soil media can be placed under paved surfaces that are designed for walking and vehicles. This allows tree roots to grow without damaging the pavement, while filtering and taking up stormwater. Stormwater not used by the trees percolates into the ground or enters the storm drain system through the underdrain.

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Pervious Pavers

Pervious pavers allow stormwater to pass through the pavement unlike traditional concrete pavers where it runs off into the storm drain system. Below the surface, permeable layers capture pollutants and store stormwater. Stormwater percolates into the ground, and excess flows into the storm drain system through a perforated underdrain.

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A layer of large permeable stone on top of native soil. The perforated underdrain is placed in this layer.
The pervious pavers are set into a top layer of permeable stone bedding.
Joints between pervious pavers are no wider than traditional concrete pavers since water can pass through the pavers.
Pavers have to be maintained and cleaned to remain pervious.
During a rain event, water passes through the pervious pavers but not the traditional asphalt surface shown in front.
During a rain event, water passes through the pervious pavers but not the traditional asphalt surface shown in front.
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A layer of medium permeable stone is spread on top of large permeable stone.
Joints between permeable pavers are wider than traditional concrete pavers to allow water to pass through in between pavers.
Permeable pavers used as surface covering for parking spaces.
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Permeable Pavers

Permeable pavers are concrete pavers installed with wider than normal joints to let stormwater pass through the joints between the pavers. Below the surface, permeable layers capture pollutants and store stormwater. Stormwater percolates into the ground, and excess flows into the storm drain system through a perforated underdrain.

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Bioretention Area

Bioretention areas use plants and soil to slow and filter stormwater. Mimicking a natural process, bioretention areas allow for ponding of stormwater, filtering it through the planted area and through biotreatment soil media. The filtered water then percolates into the ground where it can replenish groundwater. Where site conditions don’t allow for this infiltration, a perforated underdrain sends the treated water to the storm drain system.

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The bioretention area after plant installation and mulching.
Native soil is excavated, and cutoff walls are constructed around the bioretention area site.
Plants are positioned for planting into the biotreatment soil media.
Plants suitable for use in bioretention areas include those tolerant of both dry and wet conditions such as California Gray Rush (Juncus patens).
Overflow inlets prevent flooding during larger storm events.
Curb cuts divert runoff from the parking lot into the bioretention areas for treatment.
Curb cuts divert runoff from the parking lot into the bioretention areas for treatment.
Participants of a Green Infrastructure training workshop inspect one of the bioretention areas at the demonstration project site.
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Drought tolerant, low maintenance plants like this low-growing sage (Salvia Bee’s Bliss) conserve water and reduce waste.
Bioretention areas slow and filter stormwater, protecting water quality and replenishing groundwater.
A diversity of plants that are adapted to the site’s microclimate helps resist diseases and pests. Amending the soil with compost improves soil health and saves water.
A layer of mulch suppresses weeds and helps the soil retain moisture.
Flowering plants like this low growing rosemary provide habitat and food for beneficial insects and other wildlife.
Native plants like this blue-eyed grass (Sisyrinchium bellum) create wildlife habitat.
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Bay-Friendly Principles

Creating a “Bay-Friendly” rated landscape, such as the Green Infrastructure Demonstration Project at Turner Court, means working with nature to reduce waste, while protecting watersheds and communities. The seven Bay-Friendly Principles include:

  • Landscape Locally
  • Landscape for Less to the Landfill
  • Nurture the Soil
  • Conserve Water
  • Conserve Energy
  • Protect Water and Air Quality
  • Create Wildlife Habitat
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Flow-Through Planter

Flow-through planters are self-contained systems that collect roof runoff and filter it as it percolates through the biotreatment soil media and permeable material below. Water not used by the plants enters the storm drain system through a perforated pipe at the bottom of the planter. Flow-through planters can be used to treat stormwater where infiltration is not desired, such as next to buildings, or where it is not possible due to poorly draining soils and steep slopes.

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Construction of the flow-through planter in place.
The finished planter with underdrain and overflow/cleanout pipes visible.
Flow-through planters can be used to treat stormwater where infiltration is not desired, such as next to buildings.
Plants suitable for flow-through planters must be tolerant of both dry and wet conditions, like California Gray Rush (Juncus patens).
Large cobbles are used as splash rock to reduce the impact of water entering the planter through the downspout.
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Stone bedding is poured and leveled in preparation for the vault to be placed.
Delivery of the prefabricated system to be assembled in place.
The concrete vault with perimeter void spacer and containment mesh.
A crane is used to lift the concrete vault in place.
The concrete vault is connected to the catch basin with manhole and curb inlet.
Finished installation
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Horizontal Flow Biofiltration

Horizontal flow biofiltration systems, often referred to as “modular wetlands,” treat high flow rates in a small footprint. After passing through a trash screen, stormwater flows into the void space within the vault perimeter. Moving horizontally, the stormwater filters through biotreatment soil media, and then enters the storm drain system through the underdrain.