Managing Rainwater with Low-Impact Development (LID) for LEED Credits
Rainwater management is a critical aspect of sustainable building practices, and it is recognized as an important credit in the Leadership in Energy and Environmental Design (LEED) certification system. One specific LEED credit related to rainwater management is the treatment of run-off from pollutant-generating impervious surfaces using low-impact development (LID) practices. This credit focuses on replicating natural site hydrology processes and retaining on-site the runoff from rainfall events using LID and green infrastructure (GI) practices.
The LEED credit for rainwater management is based on the percentile of regional or local rainfall events that are retained on-site. The goal is to retain the runoff from at least the 80th percentile of rainfall events, which is a significant amount of precipitation. This can be achieved through various LID strategies, both structural and non-structural, that are designed to mimic natural hydrological processes.
Examples of acceptable LID techniques for rainwater management include planting rain gardens with native or adapted plant material, installing vegetated roofs, using permeable paving, and installing permanent infiltration or collection features such as vegetated swales, rain gardens, or rainwater cisterns. These techniques allow for the infiltration, evapotranspiration, or collection and reuse of rainwater on-site, reducing the amount of runoff that leaves the site and contributes to stormwater pollution.
A combination of LID approaches is recommended, although not required, as they provide holistic measures that maximize benefits. In contrast, conventional stormwater techniques, also known as grey infrastructure, such as detention or retention ponds, pipes, and vaults, may be accepted only if integrated within a holistic LID system.
One important aspect of the LEED credit for rainwater management is the prohibition of the use of coal tar sealants in any application exposed to stormwater, wash waters, condensates, irrigation water, snowmelt, or icemelt. This is because coal tar sealants contain harmful pollutants that can contaminate runoff and contribute to water pollution.
To determine the percentile amount of rainfall to be retained, daily rainfall data and the methodology provided in the U.S. Environmental Protection Agency (EPA) Technical Guidance on Implementing the Stormwater Runoff Requirements for Federal Projects under Section 438 of the Energy Independence and Security Act should be used. This ensures that the rainwater management practices are based on scientifically sound data and calculations.
In conclusion, managing rainwater through low-impact development (LID) practices is an important aspect of sustainable building practices and is recognized as a credit in the LEED certification system. By replicating natural site hydrology processes and retaining on-site the runoff from rainfall events, LID strategies such as rain gardens, vegetated roofs, permeable paving, and infiltration or collection features can effectively reduce stormwater pollution and contribute to a more sustainable built environment. Proper calculations and adherence to EPA guidelines ensure that rainwater management practices are based on sound scientific principles and contribute to achieving LEED certification.
Based on the information provided, here’s an example of a table that lists the compliance criteria and required documents for a rainwater management credit related to treating run-off from pollutant-generating impervious surfaces using low-impact development (LID) practices:
| Compliance Criteria | Required Documents |
|---|---|
| Treat run-off from pollutant-generating impervious surfaces using LID practices | Project plan or design drawings detailing the LID practices to be implemented, such as rain gardens, vegetated roofs, permeable paving, or permanent infiltration or collection features |
| Retain on site the runoff from the developed site for at least the 80th percentile of regional or local rainfall events | Rainfall data and calculation methodology as per U.S. EPA Technical Guidance on Implementing the Stormwater Runoff Requirements for Federal Projects under Section 438 of the Energy Independence and Security Act |
| Prohibit use of coal tar sealants in any application exposed to stormwater, wash waters, condensates, irrigation water, snowmelt, or icemelt | Documentation confirming that coal tar sealants will not be used in any application related to stormwater management |
| Use a combination of LID approaches to maximize benefits (recommended but not required) | Project plan or design drawings detailing the combination of LID practices to be implemented, and how they will work together in a holistic LID system |
| Grey infrastructure devices (conventional stormwater techniques) may be accepted only if integrated within a holistic LID system | Project plan or design drawings detailing how the grey infrastructure devices will be integrated within the LID system |
sample multiobjective questions with answers for the rainwater management LEED credit:
Question: What is the purpose of using low-impact development (LID) practices for rainwater management in a LEED project?
Answer: The purpose of using LID practices is to treat run-off from pollutant-generating impervious surfaces, retain on-site the runoff from the developed site for at least the 80th percentile of regional or local rainfall events, and promote sustainable stormwater management.
Question: Which of the following techniques can be used as LID practices for rainwater management in a LEED project?
a) Planting rain gardens with native or adapted plant material
b) Installing vegetated roofs
c) Using permeable paving
d) Installing permanent infiltration or collection features
e) All of the above
Answer: e) All of the above
Question: What is the minimum percentile of regional or local rainfall events that must be retained on-site in a LEED project to earn rainwater management credits?
Answer: The minimum percentile of regional or local rainfall events that must be retained on-site is the 80th percentile.
Question: Which of the following is NOT an acceptable technique for rainwater management in a LEED project?
a) Planting rain gardens with native or adapted plant material
b) Using coal tar sealants
c) Installing permeable paving
d) Installing vegetated roofs
Answer: b) Using coal tar sealants
Question: What is the purpose of using daily rainfall data and the EPA methodology in a LEED project for determining the amount of rainwater to be retained on-site?
Answer: The purpose is to determine the percentile amount of rainwater to be retained on-site as per the U.S. EPA Technical Guidance on Implementing the Stormwater Runoff Requirements for Federal Projects under Section 438 of the Energy Independence and Security Act.
Question: Which of the following is NOT a benefit of using LID practices for rainwater management in a LEED project?
a) Reducing stormwater runoff and erosion
b) Enhancing groundwater recharge
c) Improving water quality by reducing pollutants in runoff
d) Increasing energy consumption
Answer: d) Increasing energy consumption
Question: What are the examples of acceptable LID practices for rainwater management in a LEED project?
Answer: Examples of acceptable LID practices include planting rain gardens with native or adapted plant material, installing vegetated roofs, using permeable paving, and installing permanent infiltration or collection features.
Question: How can conventional grey infrastructure devices be accepted in a LEED project for rainwater management?
Answer: Conventional grey infrastructure devices, such as detention or retention ponds, pipes, and vaults, may be accepted only if integrated within a holistic LID system (i.e., a combination of LID techniques).
Question: What is the recommended approach for rainwater management in a LEED project?
Answer: The recommended approach is to use a combination of LID approaches as they are holistic measures that maximize benefits.
Question: What documentation may be required to earn rainwater management credits in a LEED project?
Answer: Documentation such as project plans or design drawings detailing the LID practices to be implemented, rainfall data and calculation methodology as per U.S. EPA Technical Guidance, and confirmation of not using coal tar sealants may be required to earn rainwater management credits.