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Studio Project Green Infrastructure Strategies, Schematics, and Calculations

Amy Lopez

1. Introduction

Nestled at the base of Angel’s flight is a green, vegetative oasis amongst the

surrounding gray infrastructure. Plants have a cooling effect on the surrounding

microclimate during the evenings. This is becoming vitally important during our

record-breaking hot periods in our summer months. However nice this patch of land

may be, it is currently completely fenced off and locked up tight. This does not stop

smaller living species from enjoying the site, but what about the larger, flightless

creatures? Humans, their furry companions, and other large night-dwellers should be

able to enjoy this mirage as a true oasis.

Located on 4th Street between Olive and Hill Streets in Bunker Hill, Downtown

Los Angeles is where this Green Infrastructure project will be located. As a spin-off

from the design studio project, this site is part of a linear park system that meanders

horizontally and vertically through Downtown Los Angeles. This masterplan utilizes a

series of shortcuts, longer cuts, and public plazas both under and over the existing

infrastructure with the mission to separate pedestrians from the grid-like roads

dominated by vehicles. This falls in line with Los Angeles’ current Vision Zero mission

to end all traffic deaths on the street by 2025.

1.1. Project Goals

Zooming back into the project site, the proposed design introduces three tiered

concrete “ring” platforms that do away with the fencing and allow visitors places to both

wander and relax. In order to keep much of the vegetative area, the platforms that

advantage of the deep inclined slope that naturally occurs. Each platform only touches

base with the ground at the highest elevation and stays plateaued at this height as it

reaches across the site where the largest ring protrudes over the 4th and Hill Streets

intersection. The cantilevered look will keep the concrete platforms well circulated a lot

of their bottom surface will be exposed to the cool air affect the vegetation at ground

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level will release, trapping the cool air under the platforms. Areas are cut out of the

platforms to allow trees to pass through and become the tallest canopy that will trap in

cool air that has left from under the platforms.

These platforms are sloped inwards to capture stormwater that drips down the

central vein into the subterranean art gallery cave underneath the plaza. Stormwater

will collect down here with other sources of water that comes from the surrounding

buildings. The high-density Angelus Plaza senior living apartments to the north-east of

the project site is a great source of graywater to add to the collective water bank. The

water feature at California Plaza above and to the north of the site drains connects to

this water bank after use. Some of this water will be used to irrigate the landscape but

always returns to the storage bank where the water will be used in correlation with

integrated swamp coolers to combine with the landscape evening cooling effect that will

keep summer temperatures down for visitors. One other source of water will come from

the condensation buildup on the lower-level cave ceiling emitted from the planting in

that area. The cave wraps around the pedestrian footpath to allow the water to roll off

the walls and collect at the lowest point in the cave floor. These plants are supported by

the sun-infiltration through cave openings, artificial lighting for the gallery, CO2 produced

by visitors breathing, and the water located at the base of the cave.

The purpose of this Green Infrastructure project is to integrate water

management recycling programs to help influence microclimate temperature mitigation

by use of swamp cooling techniques all while keeping ecological instigation a common

theme throughout the site, above and below ground level. All water will eventually

infiltrate down into the ground.

1.2. Case Studies

Relevant case studies for this project include the My Figueroa Complete Streets

project near the Staples Center in South Park, Downtown Los Angeles. This case 1

study is relevant due to the integration of landscaping in the public right-of-way. Similar

projects that are part of the Bureau of Street Services’ Complete Streets can be studied

1 https://myfigueroa.com/

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for their stormwater inlet and outlet curbs. This project can be seen as having been

inspired by these projects and Vision Zero to further push the mission goal in each. For

the stormwater case studies, the time and distance water goes through after it enters

the site until it leaves is extended so the water is recycled and repurposed for a greener,

cooler purpose.

2. Benefits Calculations

Calculations to determine the cooling microclimate effects to combat Urban Heat

Island characteristics are situated within context statistics and other related information.

As a intro to the calculations, a series of context data is presented.

The US Soil Survey data shows that the project site lays on Alfisols. These

clay-enriched subsoils have a high count of calcium, sodium, potassium, and

magnesium. Having a high number of minor nutrients available removes the need to

replenish nutrients with fertilizers, eliminating the chance for heavy metals found in such

products to enter the water flow. Leaving leaf litter where it falls is another way to

ensure nitrogen is recycled into the plants. This is not the usual habit taken by cities

due to the messy look, but it is necessary to ensure peak performance with minimal

effort.

The Los Angeles Almanac states annual average precipitation for downtown LA

is 14.70 total inches of rainfall since 1877.

CO2 emissions in downtown LA are listed as being in the highest grouping, equal

to emissions found on streets that extend past downtown LA. Integration of vegetation

to cover the site will utilize some of the built up CO2 from the vehicular network.

2.1. Methodology Narrative

The California EPA developed a formula to calculate the Urban Heat Island Index

(UHII) for each census tract in 2015. This project site is in census tract 1712 as a part

of the Southern California zone. The UHII scores are based on hour-by-hour

atmospheric modeling over two, three-month long summer sessions (June, July,

August). Years modeled include 2006, particularly for its notable heat wave, and 2013

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for being the most recent data available at the time of the UHII development. The

formula developed to determine each census tract UHII is as follows:

Whereas Tu,h is the urban temperature at time-step h , T nu,h is the non-urban

time-step at h, H is the number of time-steps, and k is the location index (i.e. census

tract). This calculation integrates, or sums up, over the designated period of time (June,

July, August) over all hours including day and night. The “min” operator is a filter that

ensures that data for the UHII is only recorded when the urban temperature is higher

than the neighboring non-urban UHI reference temperature. 2

By using the formula developed by the California EPA with the plug-in data from

the census tract the project site is in, calculating the effects the green infrastructure

strategies will have on the site are as easy as replacing the existing site data. This

develops a baseline formula from which further calculations will be referenced against to

determine the severity in which the site is able to cool down the microclimate UHII. The

big problem here is that while CalEPA has released their formula for calculating the

UHII, they did not release the individual formulas with each census tract variables. This

means that only the results are available and not the ability to insert different variables

unless there is access to the WRF-ARW simulation model CalEPA used (more

information below).

Variables that will reflect the new green infrastructural elements include the

albedo and emissivity of each material used on site by their area (square footage). It is

beneficial to have materials that are high in solar reflectance, high in far-infrared

emissivity, low far-infrared reflectance, and low solar absorption. The light-colored

concrete used in the project has a solar reflectance of 0.40, a far-infrared emissivity of

0.89, a far-infrared reflectance of 0.11, and a solar absorption rating of 0.60. The

“cantilevered” extensions of the concrete platforms are raised above ground to help

2 Creating and Mapping an Urban Heat Island Index for California. CalEPA. 2015

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lower the heat released from the solar absorption, as does the upper tree canopy that

shades the platforms. If a white coating were to be added to the surfaces, they would

have an albedo of 0.75, a surface temperature of 112°F during heat, and an emissivity

of 0.90 (is the case of all colors of paint including white). The water pooling at the

central vein before it reaches the height needed to drain into the lower level has an

emissivity of 0.91. 3

CalEPA used the WRF-ARW (Advanced Research Weather Research and

Forecasting) suite of models, with custom tweaks, to develop their UHII results.2 The

WRF-ARW is a numerical weather prediction and atmospheric simulation system that is

flexible enough to be used on supercomputers down to laptops and can focus in on

large eddy or up to global simulations. The ARW (Advanced Research) is a subset of

the WRF that includes a dynamic solver, physics options, initialization capabilities,

boundary conditions, and grid-nesting techniques, prepares the terrain, land-use, and

soil-properties input. It is the flexibility and the small-scaled analysis properties that 4

make this model appropriate for developing a UHII by census tracts. A diagram laying

out the data flow of the model is seen below.2

3 Urban Heat Island Lecture Notes 4 Skamarock et al. 2008

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The next figure is a map that shows the resultant data for my project site, located

in census tract 1712:

The UHII is in units of degree-hours per day on a Celsius scale, which reads at 40.5.

As an example, an increase of 1-degree over an 8 hour period would equal to 8

degree-hours. An increase of 2-degrees over a 4 hour period would also equal 8

degree-hours. 5

Once again, since CalEPA only released the results of their formula

computations and not the variables used for each census tract, it is not possible to plug

in different variables into the formula. Hours of various research trying to find a formula

that has an example that would allow for the input of the sites albedo and emissivity

have come up empty handed. Access to the modeling programs and the knowledge of

how to use these simulations are the only way to determine the UHII with custom

variables. The best that can be done is to calculate the project site’s current albedo and

5 Understanding the Urban Heat Island Index

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emissivity against the proposed, greener albedo and emissivity to determine the

percentage of change.

2.2 Calculations

The existing albedo for the project site is broken down by material. The entire

project site is 2.99 acres. 1.92 acres of the site is made up of long grass, which has an

albedo of 0.30. 0.38 acres of the site is made up of concrete with an albedo of 0.23.

The highly-reflective roof over the Metro Red Line entrance is at an albedo of 0.65. The

low albedos makes the temperature hotter as the materials absorb the sunlight heat and

release it in the evening.

1.21 acres of the proposed design is now landscaping which has an albedo of

0.25 (shorter than existing). 2.90 acres are now white-coated concrete that has an

albedo of 0.70. This greatly increases the amount of sunlight that is reflected back

outwards. Compared to the 1.92 acres of long grass at an albedo of 0.30, the albedo

has been increased to by 0.40 with an additional 0.98 acres.

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3. Discussion + Conclusion

There are severe limitations when trying to determine the UHII for any project

site. The models and technology needed to determine this are beyond the capabilities

of a singular person. It took an a multitude of people working at CalEPA to develop the

UHII for California’s census tracts. Even they had to use models and computations

taken for previous studies done by even more people combined. This is why it was only

possible to predict the cooling effect the proposed project design would have on the

microclimate by use of albedo calculations of materials used. By extending this

proposal to other unused green sites in the remaining Bunker Hill neighborhood, there

would be a significant increase of reflectivity of the incoming sunlight. As for the

surrounding non-green areas such as building roofs, parking lots, and streets, a white

paint added would increase the reflectivity as well. Introduction of green spaces to

these areas, while reducing albedo, will still cool down these areas by providing shade

over heat-absorbing materials, as well as introducing evening cooling effects the trees

provide. The biggest obstacle for deployment would be the skyscrapers of the

neighboring Financial District. Their tall extrusions are the reason for the urban heat

island effect in the first place, so it would be hard to propose to shorten the buildings or

reduce the reflectivity of the windows in order to prevent sunlight from bouncing around

in the skyscraper corridors.

The introduction of the proposed design on the surface is to be connected to the

underground cave and swamp cooler system that will even further bring down the

temperature of the microclimate. Introduction of these swamp coolers that bring in

graywater from the skyscrapers can greatly reduce the temperature. The fact that

Downtown Los Angeles does not have much landscaping means that there is no worry

about the humidity being too high for the swamp coolers to stop working (as seen in the

high desert areas with their introduction of more households with landscaping). An ideal

location for these swamp coolers would be in the ground-level corners of skyscrapers

where the graywater can drip down into them and the coolers are exposed to the

high-wind corridors between skyscrapers. This way, the wind corridors will push the

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cool air into the rest of the right-of-way sidewalks where most homeless people sleep

overnight (those who are at the highest risk of overheating during high evening

temperatures).

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4. Studio Project Visual Communication Materials

Top View shows

the extent of the

tiered platforms

with landscaping

re-integrated back

into the site. The

central vein where

stormwater drains

to the lower-level

cave can be seen.

Mega Drawing with

cutouts to show

platform depth and

location of art

gallery cave below

ground level. Also

shows relation to

California Plaza

above and to the

north.

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View from

across Hill

Street looking

west

showcases the

three tiered

platforms with

cutouts to

allow for trees

to surpass and

create the

top-most

canopy layer. Also shows how platforms are raised to allow for air circulation below.

View from

inside the

plaza

overlooking

the central

vein and

corten steel

panel that

allows for the

water to collect

at the low point

before draining

through vein. The view looks out towards the south.

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View from

inside the

lower-level

cave at a point

where the

cave breaches

up through the

ground level to

allow for sun

infiltration to

support

vegetation. Looks out to the south.

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5. Bibliography

CalEPA, Haider Taha, and William Dean. "Creating and Mapping an Urban Heat Island Index

for California." April 24, 2015.

"Emissivity Coefficients Materials." Engineering ToolBox. 2003.

https://www.engineeringtoolbox.com/emissivity-coefficients-d_447.html.

"Heat." Urban Green-Blue Grids for Sustainable and Resilient Cities.

https://www.urbangreenbluegrids.com/heat/#heading-2.

Skamarock, William C., Joseph B. Klemp, Jimy Dudhia, David O. Gill, Dale M. Barker, Michael

G. Duda, Xiang-Yu Huang, Wei Wang, and Jordan G. Powers. "A Description of the

Advanced Research WRF Version 3." June 2008. doi:10.5065/D68S4MVH.

"Understanding the Urban Heat Island Index." CalEPA.

https://calepa.ca.gov/climate/urban-heat-island-index-for-california/understanding-the-ur

ban-heat-island-index/.

"Urban Albedos." 2012.

https://scied.ucar.edu/sites/default/files/images/activity/urban_albedos2_0.pdf.