Our Damn Asphalt: Reclaiming Parking Lots for Sustainable Stormwater Treatment and Re-Use Overview What if parking lots’ secondary function was to serve as a space for cars with the primary function to perform ecologically? Surface parking is all across our landscape with potential to serve as stormwater filter devices. Through proper planting design and materiality, bioretention and groundwater recharge can be achieved by means of existing sheet flow across asphalt. By rethinking parking lots’ complete set of functions, we can allow a framework for an ecologically performative landscape. Narrative The existing problem stems from a byproduct of how water is discerned and dismissed rather quickly across the American landscape—usually untreated. Our much paved “suburban fabric” has greatly altered the hydrologic cycle that of recharging aquifers and providing ecological habitat. Monotonous parking lots everywhere have become some of the most noticeable, yet ignored features in our built environment. Why is storm water and gray water seen as a waste, when in fact, it is actually an on-site resource? Rethinking the use of water can be the means to resolve self-afflicting environmental issues, while making larger systems more efficient and less costly. The project location is summarized by a densely populated college town in a rural, ridge and valley setting. Suburban sprawl has dramatically affected the watershed by paving over much of the natural topography and sending high volumes of runoff into trout-filled streams. Nowhere has this problem of excessive impervious surface more evident than the typical big box retail parking lot. Compromising water quality and increasing stream erosion are consequences of these development patterns. With so much space assigned for surface parking, hundreds of acres of asphalt redirect water straight to the drain, bypassing opportunities for ground water recharge or re-use. The environmental impacts of so much impervious surface include water quality degradation and urban heat island effect. The following principles begin the conversation of how we can amend our automobile-centric landscape: 1. Rethinking how designers can control and use storm water as a public amenity to create value. 2. Re-vegetating impervious parking lots to restore ecological habitat and create more canopy coverage for infiltration and heat island effect reduction. 3. Reclaiming on-site materials to promote a sustainable post-development model. Whether stormwater is being intercepted in tropical, dry, middle latitude, or continental climates, these general materials can be used in order to reclaim maximum material, utilize plants with year-round interest, and be as low-maintenance as possible. The design strategy for this proposal includes the following primary components:
1. Excavated asphalt from parking spaces to be reclaimed as mulch surrounded by larger chunks (as stepping stones) in the immediate forebay. 2. Separate the newly assigned parking space into easy to maintain and functional geometries that imply a “no-parking” zone. 3. Using a mixture of gridded canopy trees to contrast massings of understory ferns, nomow fescues, water-loving sedges, and perennials to create a balanced year-round aesthetic. 4. Mulch is easily replaced every two years to remove heavy metals and car emissions to prevent them from percolating into the ground water. 5. Snow can be plowed and piled in these specific bioretention parking spaces where plants are more salt-tolerance. The design takes cues from existing parking lot symbology and function while catering to the performance of water. After looking at existing parking typologies, retrofitting this design in parking lots can detain and cleanse stormwater runoff to display sustainability to the public. Five possible options for implementation include: 1. 2. 3. 4.
Replacing end parking spaces with bioretention cells. Creating a formal line that cuts through or across the parking lot. Using plants and stormwater amenities to establish storefront thresholds. Substituting parking spaces with bioretention modules of two, four or eight spaces before drain inlets. 5. Providing flexible overflow pervious parking and infiltration swales that direct runoff to bioretention cells.
When the prominence of big box retail comes to an end, what and who will use these massive spaces? With the decline of these stores, the buildings’ materials provide an opportunity to reclaim and insert the infrastructure into the landscape. There are many surface activities in parking lots such as eating, waiting, reading, drinking, and more with no real programmed space. Perhaps the retail value can be improved by creating parks in parking lots that already have people but no “place”. Green gathering space, public gardens, and tree canopy can become community anchors, whether it is for an existing grocery store or future community gardens that need water for irrigation. Reclaiming parking lots for sustainable stormwater treatment and re-use is the solution for our “damn asphalt” parking lots everywhere.
Colonnade Shopping Center
Oakwood Park Woodycrest Park
Suburban Park
University Arboretum
Tudek Memorial Park
University
Park Hills Park Homestead Park
[Regional Context] Parking lots are everywhere.
Downtown
0
250 500
1000(ft)
Existing Condition 1,578,367 SF Total Area 1,398,708 SF Impervious 88.6% Impervious
Proposed Intervention 752,111 SF Pervious Area 47.6% Impervious 100,712 SF
41,820 SF
126,450 SF
89,610 SF
0
60
180(ft)
[Site Plan] Specific problems in big box retail parking lots include post-development issues such as stormwater management, creating urban heat island effect, and a sense of placelessness for both ecological habitat and people.
[Post-Development Impacts] Traditional stormwater design with its storm drain inlets, subsurface piping, and a generic detention basin causes a significant change in the hydrologic cycle, aquifer health, and ecological habitat.
RETHINK Infiltration
Bioretention
Permeable
Canopy
Excavated
Reclaimed
REPLANT RECLAIM [Concept] Rethink stormwater. Replant impervious surfaces. Reclaim excavated asphalt.
1-2% Runoff Longitudinal Crown
2-4% Runoff
2-4% Runoff
Inverted Crown Cross Slope to Low Point
Cross Section Crown
Central Ridge Slope to Interior
Option One
Option Two
Option Three
Option Four
Option Five
Replacing end spaces
Creating an axial line
Storefront thresholds
Scattered before drain inlets
Flexible overflow parking
[Parking Typologies + Options] Retrofitting this design in parking lots can detain and cleanse stormwater runoff to display sustainability.
1. Gravel, stones
2
2. No-mow fescue / sedges +
3
1
+
3. Canopy trees + ferns
2 Typical parking spaces
French drain to capture runoff
Forebay + Retention
(3”) Asphalt Pavement (4”) Crushed Stone Base Prepared subgrade (6” ht.) Metal Edging (18” wide) x (24” deep) trench 1” Washed Gravel fill (4”) diameter perforated drain pipe
[Design Process] The design takes cues from existing parking lot symbology while catering to the function and performance of water movement.
“No-parking�
Metal edging Mulch
French drain with washed, large river stone
Recycled concrete or asphalt chunks
Gridded closed canopy Asphalt Gravel
Low-lying shrub masses
[Materiality] As big box retail stores decline, an opportunity to reclaim and insert the infrastructure into the landscape becomes available.
Canopy trees
Understory ferns Shrub massing Reclaimed asphalt and concrete River stone filled runnel cut into existing asphalt
Continental Climate
Moderate Climate
Dry Climate
Tropical Climate
Quaking Aspen, Alder, Larch Bald Cypress, Dawn Redwood New England Aster Marsh Marigold Cinnamon Fern
Plane Tree, River birch Douglas Fir, Coast Redwood American Elderberry, Dogwood Switchgrass
Red Maple, Sweet Gum Balsam Fir, Serviceberry Toad Lilly Northern Sea Oats Grass
Mangrove Fan Palm, Everglades Palm Taro Blue Fescue Canna
[Planting Design] Native vegetation that creates habitat with year-round interest and is water tolerant.
Runoff
Runoff
Bioretention soil Existing soil
Prepared subgrade
Existing soil
[Capturing the First Flush] Bioretention cells include mixed planting of flood tolerant trees, shrubs, grasses, sedges, and groundcovers.
(4�) Concrete turf grid (1�) Sand setting bed (4�) Aggregate Drainage membrane Prepared subbase
[Overflow Parking] A meanderings infiltration-swale leading to the existing detention basin redirects and slows down water along the perimeter of the site. A gradient of turf-grid pavers becomes more prevalent as one moves away from retail.
Maximum ponding High water table Amended topsoil Low water table
2’ Bioretention soil mix Geo-textile fabric (optional) 1’ Drainage Stone 6” PVC Pipe to collect water for re-use
[Infiltration-swale] If future redevelopment replaces big box retail stores, infiltration can help control water volume without eliminating too much parking.
Rubber hose at bark (3) Guy wires (3) Galvanized turnbuckle
(3�) Organic mulch Create saucer with topsoil Finish grade Wood deadman Root ball Planting mix backfill
Prepared soil base Prepared subgrade
[Transplanting] Trees that are young or in poor condition can be transplanted according to water tolerance.
1
Greywater Wetlands
2
Recreation
3
Market / Event Space
4
Community Gardens
5
Bioretention Gardens
6
Native Gardens
7
Viewing Landform
1
5 2
3
4
5
2
1 5
6
2
7 2
0
[Big Box Retail Vacancy] When the prominence of big box retail comes to an end, what and who will fulfill these massive spaces?
20 40
[Masterplan] After determining where water can be infiltrated, vegetation and excavation create filter devices throughout the site.
SW / GREYWATER FOREBAY
SW/ GREYWATER TREATMENT
WATER COLLECTING PERMEABLE PAVERS
Existing Contours
Stormwater Runoff
Sub-surface Utilities
Slope
[Stormwater Strategy] Stormwater falls and is intercepted in water collecting devices that are piped or redirected to treatment bays.
[Creating Parks in Parking Lots] Green gathering space, public gardens, and tree canopy cover become community anchors in years to come.
[A Community Anchor] Circulation and form recalls the former parking lot and creates community space that embodies a sustainable landscape and lifestyle
for residents and users.