Stormwater management

 

At Green Light Home Builders, LLC, we are proud to do our part in managing stormwater responsibly.  The stormwater best management practices, or BMP’s, that we use are critical parts of our approach to sustainable residential construction.  Our site planning process for every major renovation or new house that we build includes a plan to manage stormwater temporarily during the construction process and permanently after the project is completed.

 

This article features a stormwater management system that we installed for a major exterior renovation of a home in Montreat, NC.  It includes a parking area drainage system connected to an infiltration trench that has a significant impact on the runoff not only from the property we worked on, but from the portion of the street uphill from that property.  Rainwater collects at two catch basins in the gravel parking area and flows through pipes under the parking area, through a concrete retaining wall, and down into two large storage pipes after passing through a sump basin where sediment and debris can settle out and be removed.  After it reaches the storage pipes, it infiltrates into the soil below and around the trench, instead of leaving the site as surface runoff.

Regular cleaning of the sump basin helps to prevent the build-up of silt in the system.

Regular cleaning of the sump basin helps to prevent the build-up of silt in the system.

The sidewalls of the excavated trench are scarified before backfilling to increase infiltration rates.

The sidewalls of the excavated trench are scarified before backfilling to increase infiltration rates.

These 12" perforated drain pipes serve as an underground storage basin for stormwater.

These 12″ perforated drain pipes serve as an underground storage basin for stormwater.

 

Gravel is backfilled over the pipes and encapsulated in geotextile fabric to keep sediment from entering and clogging the system.

Gravel is backfilled over the pipes and encapsulated in geotextile fabric to keep sediment from entering and clogging the system.

 

This system makes a positive impact on the hydrology and ecology of the watershed in a few ways.  First, it promotes groundwater recharge by infiltrating up to 50 cubic feet of runoff that would otherwise flow down the hill towards the nearest creek or river. This is water that naturally would have infiltrated into the ground if not for nearby rooftops and paved surfaces that redirect it toward stormwater collection points.  Second, by reducing the total volume of runoff headed towards surface waters, it reduces the velocity of the runoff, thereby reducing erosion and sedimentation that is harmful to aquatic life and habitat.  Lastly, it improves water quality and helps to reduce the artificially elevated temperature of the nearby creeks by capturing the warm, polluted runoff that has flowed across hot rooftops, pavement and gravel.  All of these things help to mitigate the impact that people have on the environment through land development and building.

These same goals can be achieved through a number of effective and creative methods.  The infiltration system we have discussed here required a fair amount of design, calculations, and testing during its construction. Trained in the design of stormwater best management practices, Caitlin Sloop, ASLA is a valuable resource to us on projects like this one. With her help, we have designed and constructed a number of systems that reduce stormwater impacts in different ways.  Some examples are as simple as using rain barrels and cisterns to harvest rainwater from rooftops for use in landscape irrigation, a process that is very enjoyable and rewarding to some avid gardeners for whom we have worked. Stormwater BMPs can be integrated seamlessly into the landscape design and often require minimal maintenance from homeowners, such as Bio-retention areas, or rain gardens, that are beautiful parts of the landscape designed around water-loving plants and soils.

Managing the stormwater on a site during and after construction is a responsible way to mitigate the impacts of new development.  Furthermore, with increased consciousness of these impacts, systems similar to this have become requirements on certain construction projects in many municipalities.  Here in Western North Carolina, many planning jurisdictions have wisely adopted “steep slope” or “hillside development” ordinances to protect sensitive building sites and to encourage developers to treat the land they are working on with respect and diligence, and a primary purpose of those regulations is to require proper management of the water on and around a site.  At Green Light Home Builders, we find a great sense of satisfaction in implementing systems like this one for all these reasons, whether we are complying with a requirement, helping out our downhill neighbors, or simply doing our part in protecting a natural resource that we enjoy in our time away from work.