Forested Rain Gardens / Bioretention Areas at the main parking lot at the Reedy Creek Park Entrance
Volunteer days for laying the river rock on the side slopes and planting the native trees, shrubs, and grasses will be January 21, 26 and 30, 2016.
Forested rain gardens in the parking lot medians at the Reedy Creek Park entrance (accessed off of Harrison Avenue and I-40). Phase I of construction was completed in December 2015. Half of the 2 center medians were dug up, drainage installed, and a special bioretension soil mixture, covered with mulch was installed. The storm water from the parking lot has not yet been diverted into the medians - that will happen in mid-January when we install the river rock and vegetation. Afterwards, volunteers will help plant the vegetation lay the river rock.
This project will enable the treatment of all the stormwater runoff from the 1 acre parking lot. In addition, trees will be planted that will grow to provide much needed shade.
We have received a $25,000 grant from Triangle Community Foundation. This project has been made possible with a grant from Triangle Community Foundation's Support for Places: Environmental Conservation Public Benefit program." We also previously received a $10,000 grant from the Wells Fargo Community Grant program.
We are seeking volunteers to lay the rock and plant vegetation on January 21, 22 and 23 2016. Volunteers help us keep the project costs reasonable.
This project has numerous partners:
This project should result in several environmental and user benefits, including: reduced runoff volume and intensity of stormwater runoff due to the infiltration into special soil media we will install in the medians. The trees and shrubs will provide much needed shade in the hot, steamy parking lot. The shade to reduce the thermal impact to the downgradiant streams.
Details: We will install innovative stormwater BMP of forested bioretention cells (rain gardens) within a 210 space parking lot median at William B. Umstead State Park. The parking area that will drain to the stormwater control measure is 1.3 acres. The impervious area is 1 acre; the two center medians area are 0.3 acres. We are installing 2 large bioretention cells in the northern halves of each of the center two medians. Each of the two cells will be in the median space of 18 feet wide by 180 feet long (the entire median length is 360 feet, plus the end islands). Each cell will be retrofit with 3 feet of sandy loam engineered media, a 6-inch layer of washed stone, and underdrains to convey treated stormwater. The surface will be topped with 2-3 inches of triple-shredded hardwood mulch and planted with trees, shrubs, and herbaceous perennials.
Two innovative features: 1) trees to provide shade, whose survival will be improved by an 2) internal water storage zone created by 90-degree elbows in the underdrain, which will improve nitrogen treatment and increase total annual volume reduction.
A key focus will be planting of native trees, complemented by an understory of other native vegetation that can survive in a combination of wet and droughty periods. Tree species planted (tentative list, will be updated with actual): water oak (Quercus nigra) (fast growing oak species) and bald cypress (Taxodium distichum) (slower growing, with stunning fall colors). Understory trees and bushes will include: dogwood (Cornus florida) and beauty berry (Callicarpa americana). Native grasses will include switch grass (Panicum virgatum) and river oats (Chasmanthium latifolium). As overstory tree canopy closes, shade will limit native grass growth but not understory tree and shrub growth.
We are also installing 2 monarch butterfly gardens in raised beds. They will be located along the walkway to the bath house. We will be soliciting volunteers to help construct the raised bed and plant.
Site location and Design Schematics