Green Stormwater Infrastructure article

GSI designs use multiple techniques to manage stormwater on a property the way it would behave on a greenfield lot, rather than diverting directly to storm drains, reducing the impact of the development on the downstream municipal stormwater infrastructure, especially during heavy rainfall events like Houston has seen over the years. Techniques that capture and reuse stormwater reduce potable water demands from municipal water systems, which can reduce the property’s water costs. Large amounts of energy are required to purify and distribute water at the municipal level, so reductions in water demands can reduce energy consumption as well. Many of these techniques detailed below will be limited to new developments, but some can be applied to existing properties.

GSI Techniques to Manage Stormwater

Bioretention systems, or rain gardens, can slow the rate of stormwater runoff on a property using native vegetation planted on an engineered substructure of mulch, gravel, fabric and an underdrain. The water is captured and filtered through the layers and eventually drains to the municipal stormwater system. Rain gardens provide additional wildlife habitats and improve the visual appeal of the property.

Green roofs take advantage of unused space to create a green space that can capture and use rainwater, as well as add an amenity for residents. The additional structural and drainage design requirements may limit converting existing roofs, but these can be addressed in a new development project.

Permeable pavement allows stormwater to flow through to an underdrain system or below-grade cistern; again, this slows the runoff rather than diverting the runoff directly to municipal stormwater drains like impervious materials. Permeable pay­ments combined with a rainwater harvesting system can increase the volume of water collected and available for reuse.

Rainwater harvesting systems collect water from roofs, park­ing lots, etc. for reuse on the property for irrigation, cooling tower makeup or greywater systems such as flushing toilets. Above ground storage tanks or underground cisterns can be used for the water collection. Filtration, treatment and pump systems will also be required to reuse the water, but the long-term savings in water costs can be significant. Rainwater harvesting systems can be added to existing facilities, but limited available space for large storage tanks may limit their effectiveness.

Soil amendments, urban forestry, and vegetated filter strips are all techniques to slow the stormwater runoff on a property using native vegetation and trees. These techniques can be applied to existing properties and new developments.

The initial cost to design and install GSI systems may be higher than traditional alternatives, however, the operating costs can be lower and provide a positive ROI over time for the owner and reduced expenses for the residents. In addition, four incentive programs have been proposed to offset these costs and encour­age GSI projects. Those are:

• Integrated GSI Development Rules
• Property Tax Abatements
• Award and Recognition Program
• Increased Permitting Process Certainty and Speed

Based on feedback from developers, current development rules do not promote the use of GSI techniques in new developments. New integrated GSI development rules would incentivize devel­opers to use GSI techniques by allowing an alternative set of rules for permitting that could reduce overall project costs by 2% and site costs by 34%.

Along similar lines, an alternative permitting program could speed up the permitting time and reduce costs. The recommen­dation is for a team review process where stakeholders meet for two to four hours, review the designs, make any required changes and then issue permits immediately after the meeting.

Property tax abatements are the second incentive recommend­ed in the study. By reducing future property taxes, developers can cover some or all of the additional costs related to GSI projects.

A reward and recognition program is another way to incen­tivize GSI projects in Houston, however, without the financial benefits of the other incentives proposed, a recognition program alone is unlikely to motivate developers to use GSI projects.

The report outlines the related stakeholders and a plan for implementation with timelines for all of the incentives proposed. Additionally, it is recommended that multiple incentives are used together to incentivize developers more to use GSI projects. Visit the City of Houston website to see the full report.

Although it’s not covered in the report, another incentive that could potentially be used for GSI on existing properties is Property Accessed Clean Energy funding. PACE is a financial tool that property owners can use to fund projects that reduce water and energy consumption on their property with a long-term assessment against the property with no or little initial capital expense. For more information on PACE, visit the Texas PACE Authority website.

Many of the GSI projects could also earn points toward a LEED certification through the U.S. Green Building Council. For devel­opers already pursuing a LEED certification, GSI related incen­tives may be even more desirable. For more information on LEED, visit the USGBC website.

GSI projects will have a very positive impact on the City of Houston as they increase property value and operating income, improve amenities for residents and improve stormwater drainage for the greater community. As demand for sustainable buildings increases from residents and the incentive programs offset additional costs, we will, hopefully, see it become the stan­dard practice in the not so distant future.

This article was originally published in HAA’s ABODE magazine. Click here to see the original article.