Bioretention basins consist of a ponding area, mulch layer, plants, and biotreatment soil media (BSM). They are typically underlain by drain rock and an underdrain pipe.

A bioretention area can be any size or shape. These areas filter and clean rainwater before it seeps into the underlying native soil or the City’s stormwater sewer system.

Refer to the City of San José GSI Maintenance Field Guide for maintenance guidance.

Flow-through planter boxes (FTPs) are a type of bioretention system suitable for areas where soil moisture is a potential concern and often located near buildings. They use soil and plants to treat and hold runoff while preventing seepage into underlying soil.

Treated water that is not absorbed by vegetation flows into the City's stormwater sewer system and then into the nearest creek.

Refer to the City of San José GSI Maintenance Field Guide for maintenance guidance.

A tree well filter is a type of bioretention system. It is an excavated pit or vault filled with biotreatment soil media (BSM) and planted with a tree or other vegetation. If needed, property owners can underlie them with drain rock and an underdrain.

Like a bioretention area, a tree well filter cleans stormwater runoff, but can take up less space.

Refer to the City of San José GSI Maintenance Field Guide for maintenance guidance.

Bioswales are vegetated channels designed to transport water with gently sloped sides. They concentrate or remove debris and pollution out of surface water runoff.

Bioswales absorb and infiltrate low flows. During heavy rainfalls, they temporarily store and transport runoff to storm sewer inlets.

Refer to the City of San José GSI Maintenance Field Guide for maintenance guidance.

Pervious pavement is a hard surface that lets water soak through into a gravel layer before absorbing into the ground. Examples include pervious concrete, porous asphalt, rubber pavement, permeable pavers, and grid pavement.

Unlike bioretention systems, pervious pavement does not need extra space for water treatment. This makes it a good option for areas like streets and parking lots.

Refer to the City of San José GSI Maintenance Field Guide for maintenance guidance.

Media filtration systems (MFSs) are below-ground mechanical devices that remove pollutants from stormwater runoff using various filtering media. 

Stormwater passes through screening and filtering material such as perlite, carbon, peat, or other manufactured medias.

Only qualified personnel according to the manufacturer’s specifications should maintain MFSs. Maintain them at a least every three years.

Inspect MFSs twice per year — before and after the rainy season. Property owners must maintain documentation and provide it to City inspectors upon request.

Hydrodynamic separators are below-ground mechanical devices. They capture trash, sediment, and floating debris using gravity and spinning motions. Like MFSs, they can overflow and allow untreated stormwater to bypass them once they are full.

Only qualified personnel according to the manufacturer’s specifications should maintain hydrodynamic separators. Maintain them at a least every three years.

Hydromodification measures, like detention basins, collect stormwater and gradually release it over time. This helps reduce erosion and flooding in local waterways and protect local wildlife.

Unlike bioretention basins, they do not have a special soil mix and do not need vegetation. Regular maintenance prevents sediment buildup that can reduce their effectiveness.

Refer to the City of San José GSI Maintenance Field Guide for maintenance guidance.

Vegetated STMs use plants and specialized soil to slow down and clean stormwater. This prevents local flooding and erosion by reducing the flow and filtering out pollutants.

General Maintenance Tips:

• Vegetation Health: Keep plants healthy and replace dead or unhealthy ones.
• Soil and Mulch: Use an approved soil mix to maintain proper drainage. Apply a layer of composted arbor mulch 2-3 inches thick to prevent weeds and retain moisture. For more information refer to the C.3 Stormwater Handbook.
• Irrigation and Watering: Test irrigation systems regularly, particularly during dry months. Adjust watering schedules based on plant needs.
• Ponding and Drainage: Make sure water drains within 72 hours. Remove built-up sediment that blocks infiltration.
• Trash and Debris Removal: Remove fallen leaves, branches, and other trash.

Mechanical STMs use filters and mechanical parts to filter stormwater.

General Maintenance Tips:

• Inspect the systems twice a year — before and after the rainy season.
• Maintenance should only be done by trained professionals.
• Remove trash and built-up dirt.
• Repair any damage, such as cracks or leaks.
• Replace filters as needed following the manufacturer’s instructions.
• Keep maintenance records for at least five years. Physical and electronic copies are accepted.

Special Considerations for STMs with Pumps:

• Test and clean sump pump systems at least once a year to make sure it is functioning as intended.