Solving Typical Rain Garden Problems
Many of us embraced rain gardens in the past several years for their ability to mitigate storm water runoff and to help cleanse groundwater of pollutants.
We love rain gardens; we really do. It’s just that sometimes rain gardens don’t love us back. Here are some reasons that rain gardens don’t always work, and the most likely solutions:
1. Problem: Lack of an underdrain. Rain gardens are designed to infiltrate storm water into the soil. But sometimes they fill up faster than they can drain.
Solution: Install a 4’’ perforated pipe underdrain below the rain garden basin. This underdrain operates as a kind of relief valve if excess water accumulates in the rain garden. The underdrain is connected to an outlet structure, which is there to function during intense storm events when the basin fills up.
2. Problem: Clay and silt clog the perforations in the 4” underdrain pipe.
Solution: If the rain garden stops draining, the underdrain pipe may be clogged. Flush the underdrain pipe with a garden hose via the outlet structure.
3. Problem: Sediment washes into the rain garden from surrounding surfaces, filling in all the desirable and needed air pockets in the mulch, preventing infiltration.
Solution: Protect the rain garden from sedimentation with a silt fence or filter sock until the surrounding areas are stabilized with vegetation or paving.
4. Problem: Water won’t seep into the soil. Sometimes heavy construction vehicles compress subgrade soil to a degree that water cannot infiltrate.
Solution: Loosen the subgrade before constructing the rain garden.
In Pittsburgh, Green is in the Air
It’s summer and that means the City is green with trees. Not only are plants in the midst of their growing season, but people are in the midst of launching green initiatives. Last week we attended a poster session during the Who’s Who in Green Infrastructure Implementation event hosted by the Green Building Alliance and organized by 3 Rivers Wet Weather. The event was packed with people interested in sharing their projects and learning more about green infrastructure.
This morning over 80 people packed a Pittsburgh Zoo conference room to kick-off this year’s Green Workplace Challenge (GWC), a program of Sustainable Pittsburgh. We took part last year in the challenge and are excited to enter again this year with the revamped program.
County Building Green Roof Measures its Own Effectiveness
You may think of the Allegheny County Office Building, 452 Forbes Ave., Pittsburgh, as the place to go if you have a question about your property assessment.
But this historic building is also the site of a beautiful, functional and productive green roof, designed with the help of Pashek Associates.Green roofs benefit the local environment by reducing storm water runoff; keeping buildings warmer in winter and cooler in summer; evening out daily temperature swings; and helping to mitigate the heat island effect.
The County Office Building green roof, completed in 2010, is now growing into its role as a powerful tool for protecting the environment
A network of sensors embedded in the soils monitor performance of this roof compared with a conventional “control” roof. The sensors measure roof temperature, soil moisture, water flow and water retention, with data collected every 15 minutes. Over time, this information will demonstrate the valuable role that green roofs can play in easing some of the damaging effects that development has on our environment.
Here is an example of the data that can be seen by visiting the monitoring website. This example compares temperatures in a one-month period on the control roof (top line) with temperatures recorded by two sensors on the green roof (bottom two lines).
The green roof includes four different types of growing conditions, and over time it will also be possible to learn through the monitoring system how each type performs compared with the others. They are:
- Intensive – 8 to 12 inches of soil and growing shrubs and plants needing the soil depth.
- Semi-intensive – 6 inches of soil and able to grow plants and shrubs.
- Roll out Mat – set on 4 inches of soil, this pre-grown sedum mat provides instant cover.
- Tray system – easy to install, pre-grown sedum and lightweight.
A Green Roof for a Green Convention Center
The Gold LEED Certified convention center in Pittsburgh is becoming even greener. This fall, a green roof is being constructed above the loading dock and is fully accessible to event goers.
In the summer of 2010, as planning and design was being completed for fixing a roof leak, the Sports and Exhibition Authority realized they had a golden opportunity to install and showcase a green roof that is readily accessible from meeting rooms on the third floor.
Pashek Associates was hired to design the new roof to include outdoor gathering and event space along with planting areas. The final design includes a meandering blue pathway resembling a stream, keeping with the theme of the existing architecture and meant to remind visitors of the green roof’s stormwater benefits. The path separates two contrasting types of planting areas. The first is a typical sedum planting done on most extensive green roofs. The second consists of native perennials, providing wildlife habitat. The simplicity of the design allows the building’s sculptural cable bundles to remain a focal point.
Stay tuned for photos of the ongoing construction to be completed this fall!
DCNR’s Stormwater BMP Guide for Parks
The Pennsylvania Department of Conservation and Natural Resources has recently asked us, along with some other LA’s in the State, to review and comment on their new Stormwater BMP Guide for Parks. The guide is for grantees to use and apply to their sites. Below is the final version:
Rain Garden- an excavated shallow surface depression planted with specially selected native vegetation to treat and capture runoff. Rain gardens should be located in well-drained soils. They allow stormwater to be absorbed by plants and infiltrated into the groundwater.
Pervious Pavement- consists of a permeable pavement (surface course) underlain by a uniformly-graded stone bed which provides temporary storage for stormwater runoff and promotes infiltration. The surface course may consist of porous asphalt, porous concrete, or various porous structural pavers laid on uncompacted soil.
Riparian Areas- a permanent area of trees and shrubs located adjacent to streams, lakes, ponds, and wetlands. Riparian forests are the most beneficial type of buffer for they provide ecological and water quality benefits.
Vegetated Swale- a broad, shallow channel densely planted with a variety of trees, shrubs, and/or grasses. Vegetative swales should be promoted in lieu of storm piping to convey stormwater naturally, promoting infiltration, reducing runoff volume, and filtering pollutants.
Naturalized Infiltration Basin- an earthen structure constructed either by impoundment of a natural depression or excavation of existing soil that provides temporary storage and infiltration of stormwater runoff.
Floodplain and Wetland Restoration- tries to mimic the interaction of groundwater, stream base flow, and vegetative root systems- key components of a stream corridor under pre-settlement (pre-1600s) conditions. The interaction among these elements provides multiple benefits, including the filtering of sediments and nutrients through retention of frequent high flows on the floodplain, removal of nitrates from groundwater, reduction of peak flow rates, groundwater recharge/infiltration, reduced erosion, control non native invasive species, and an increase of storage and reduction of flood elevations during higher flows.
Reforestation- replant the site with trees.
Extensive Green Roof- the most popular green roof for smaller structures and existing structures. Its lightweight attributes minimize the amount of structural changes needed to create it.
Warm Season Meadows- conversion of a turf area into a meadow. Native species should be selected for their minimum need of fertilizers, herbicides and pesticides. Minimize mowing to two times per year.
Runoff Capture and Reuse- encompasses a wide variety of water storage techniques designed to “capture” precipitation, hold it for a period of time, and reuse it. These storage techniques may include cisterns, underground tanks, above-ground vertical storage tanks, rain barrels or other systems.
You can find more information about Stormwater BMPs in the PA Department of Environmental Protection Stormwater BMP Manual here.
The Story of Our Green Roof: Part 2
Since we’ve constructed a green roof on part of our office building in late 2006, we have learned several things that we want to share:
What is Green Infrastructure?
When you think of infrastructure, you usually think of things like roads, sewer systems, water supply, power grids, etc… It is the basic physical structures needed for a community to enable, sustain, or enhance a certain standard of living for its residents. It enables the buying and selling of goods and services at a more efficient level. Could you imagine your workplace without internet, electricity, or even roads connecting you to your clients?
Wetlands and riparian buffers are green infrastructure.
But what does it mean when “green” is placed in front of the word infrastructure? Green Infrastructure is a concept that can, and should, be applied to all different scales of planning and design. Basically, it includes everything from strategically planned and managed networks of natural lands, to working landscapes, to recreational landscapes, and other open spaces that conserve ecosystem values and functions. In other words, greenways, parks, riparian buffers, wetlands, floodplains, rivers, and even stormwater Best Management Practices such as rain gardens, porous pavements, green roofs, and trees are all part of Green Infrastructure. It recognizes the importance of natural systems and processes within our communities.
Green roofs and rain gardens are green infrastructure.
Why has Green Infrastructure become so important in the last 10 or 20 years? Well, because it is beneficial for the environment, human health, the economy, and our society as a whole. Working with and using natural processes ensures that we’ll have resources for future generations. Stormwater BMPs reduce flooding, pollution, and the strain on our storm sewers. Street trees beautify our neighborhoods, increase property values, reduce the urban heat island, and absorb air pollution and stormwater. Greenways help protect steep hillsides from being developed and eroded, protect wildlife habitat, and offer recreational opportunities. Constructed wetlands not only provide wildlife habitat but filter pollution and even human waste.
So the next time you step outside, try to identify what types of green infrastructure are present and how they help to make your community a better place.
The Story of Our Green Roof: Part 1
In 2006, Pashek Associates decided to experiment with designing and building a green roof on our 1890’s office building located at 619 East Ohio Street on the Northside. We wanted to see what we could do with a little money, a little time, and a little physical labor. After discussing different options, we decided on a simple extensive tray system, mostly because the manufacturer was using them on a larger project in the city and agreed to put an extra one hundred trays on the truck and deliver them at a discounted price.
One cold December morning, we put on our working gloves and carried the 50-pound trays filled with special growing medium into place, assembly line style. Each 2’x2’ aluminum tray was set down on five small rubber pads to allow excess roof runoff to flow under the trays and into the existing roof drain. No other material was applied directly to the roof. It was as simple as that!
Then, on a warm spring day, the whole office pulled our gloves back on and planted the trays with several varieties of sedum. We used small plugs and get them a good soak using water from a rain barrel attached to our third floor roof. We did install a drip irrigation system for the first growing season. We have removed the system and haven’t needed to water the plants since.
A couple years later, we thought we had a roof leak. A roofing contractor moved the trays around the roof in order to find the leak. He was surprised to find that there was almost no degradation of the roof membrane as a result of the green roof trays. Ultimately, instead of finding a leak in the roof, the contractor found a leak in a brick wall. That’s when we knew that our green roof was really doing it’s job!
