A United States 2014 GREEN INFRASTRUCTURE TECHNICAL ASSISTANCE PROGRAM
Environmental Protection Albuquerque Metropolitan Arroyo Flood Control Authority
"Agency Albuquerque, NM
Imperial Building Site Design
On-site Treatment of Stormwater Runoff and Fugitive Flows
SEPTEMBER 2016
EPA 832-R-16-007
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About the Green Infrastructure Technical Assistance Program
Stormwater runoff is a major cause of water pollution in urban areas. When rain falls in undeveloped
areas, soil and plants absorb and filter the water. When rain falls on our roofs, streets, and parking lots,
however, the water cannot soak into the ground. In most urban areas, stormwater is drained through
engineered collection systems and discharged into nearby water bodies. The stormwater carries trash,
bacteria, heavy metals, and other pollutants from the urban landscape, polluting the receiving waters.
Higher flows also can cause erosion and flooding in urban streams, damaging habitat, property, and
infrastructure.
Green infrastructure uses vegetation, soils, and natural processes to manage water and create healthier
urban environments. At the scale of a city or county, green infrastructure refers to the patchwork of
natural areas that provides habitat, flood protection, cleaner air, and cleaner water. At the scale of a
neighborhood or site, green infrastructure refers to stormwater management systems that mimic nature
by soaking up and storing water. Green infrastructure can be a cost-effective approach for improving
water quality and helping communities stretch their infrastructure investments further by providing
multiple environmental, economic, and community benefits. This multibenefit approach creates
sustainable and resilient water infrastructure that supports and revitalizes urban communities.
The U.S. Environmental Protection Agency (EPA) encourages communities to use green infrastructure to
help manage stormwater runoff, reduce sewer overflows, and improve water quality. EPA recognizes
the value of working collaboratively with communities to support broader adoption of green
infrastructure approaches. Technical assistance is a key component to accelerating the implementation
of green infrastructure across the nation and aligns with EPA's commitment to provide community
focused outreach and support the President's Priority Agenda Enhancing the Climate Resilience of
America's Natural Resources. Creating more resilient systems will become increasingly important in the
face of climate change. As more intense weather events and dwindling water supplies stress the
performance of the nation's water infrastructure, green infrastructure offers an approach to increase
resiliency and adaptability.
For more information, visit http://www.eDa.aov/greeninfrastructure.
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Acknowledgements
Principal CPA Staff
Christopher Kloss, EPA
Jamie Piziali, EPA
Tamara Mittman, EPA
Eva Birk, EPA ORISE Participant
Suzanna Perea, EPA Region 6
Community Team
Jerry Lavato, Albuquerque Metropolitan Arroyo Flood Control Authority
David Silverman, Geltmore, LLC
Paul Silverman, Geltmore, LLC
Ron Witherspoon, Dekker Perich Sabatini
Ronald Bohannan, Tierra West, LLC
Dory Wegrzyn, YES Housing
Michelle Den Bleyker, YES Housing
David Kim, Anderson Kim Architecture + Urban Design
Robin Seydel, La Montanita Co-Op
Andrew Werth, ACE Leadership High School
Sandra Mack, Amy Biehl High School
Consultant Team
Jason Wright, Tetra Tech
Bobby Tucker, Tetra Tech
Vic D'Amato, Tetra Tech
Martina Frey, Tetra Tech
John Kosco, Tetra Tech
Robin Cunningham, Tetra Tech
This report was developed under EPA Contract No. EP-C-11-009 as part of the 2014 EPA Green
Infrastructure Technical Assistance Program.
Cover Photo: Urban Farm, Albuquerque, New Mexico
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Contents
Executive Summary 1
1. Introduction 2
1.1. Water Quality Issues/Goals 2
1.2. Project Overview and Goals 2
1.3. Project Benefits 5
1.4. Local Challenges 5
2. Design Approach 7
2.1. Cisterns and Rain Barrels 8
2.1.1. Hydrology 8
2.1.2. Water Quality 8
2.1.3. Applications 9
2.2. Bioretention Planter Boxes 12
2.2.1. Hydrology 12
2.2.2. Water Quality 13
2.2.3. Applications 15
3. Conceptual Design 16
3.1. Water Treatment Strategy 17
3.2. Treatment of Rooftop Runoff 18
3.2.1. Irrigation Demand 19
3.2.2. Water Balance Modeling 19
3.3. Fugitive Flow Treatment 20
3.3.1. Treatment Scenario 1 24
3.3.2. Treatment Scenario 2 26
3.3.3. Treatment Scenario 3 27
3.3.4. Summary 29
3.4. Planting Plan 29
3.5. Operation and Maintenance 30
4. Conclusion 33
5. References 34
Appendix A: Site Plan and Details A-l
Appendix B: Bioretention Soil Media Specifications B-l
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Figures
Figure 1-1. Location and existing condition of the Imperial Building site 3
Figure 1-2. Imperial Building: Perspective from 3rd Street 4
Figure 2-1. Rain barrels at San Pasqual Academy, Escondido, California 8
Figure 2-2. Typical plastic cisterns 9
Figure 2-3. Wood wrapped cisterns 10
Figure 2-4. Decorative cistern 10
Figure 2-5. Below-ground cistern 11
Figure 2-6. Residential rain barrel 11
Figure 2-7. Rain barrels adequately sized for contributing roof area 12
Figure 2-8. Bioretention planter box 12
Figure 2-9. Roadside flow-through planter 15
Figure 3-1. Existing urban farm at 2nd Street and Gold Avenue SW 16
Figure 3-2. Flow diagram for water reuse strategy at Imperial Building 18
Figure 3-3. Potential routing and treatment of fugitive flows 21
Figure 3-4. Typical bioretention planter box configuration 22
Figure 3-5. Tank to collect ramp runoff 23
Figure 3-6. Routing of ramp stormwater runoff 23
Figure 3-7. Treatment planter box 24
Figure 3-8. Planter boxes with a suspended pavement system 27
Figure 3-9. Self-cleaning inlet filters 30
Tables
Table 2-1. Pollutant removal characteristics of bioretention planter boxes 13
Table 3-1. Typical irrigation demands for vegetable production in Albuquerque 19
Table 3-2. Cistern performance results 20
Table 3-3. Cistern costs 20
Table 3-4. Ground-level runoff and nuisance flow treatment construction cost (Treatment Scenario 1) 24
Table 3-5. Ground-level runoff and nuisance flow treatment construction cost (Treatment Scenario 2) 26
Table 3-6. Ground-level runoff and nuisance flow treatment construction cost (Treatment Scenario 3) 28
Table 3-7. Treatment Scenario comparison 29
Table 3-8. Recommended vegetation 30
Table 3-9. Inspection and maintenance tasks for cisterns 31
Table 3-10. Inspection and maintenance tasks for bioretention planter box 32
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Acronyms
AMAFCA
Albuquerque Metropolitan Arroyo Flood Control Association
ASTM
American Society for Testing and Materials
cfs
cubic feet per second
EPA
U.S. Environmental Protection Agency
ET
evapotranspiration
ft
feet/foot
gpd
gallons per day
gpm
gallons per minute
HVAC
heating, ventilation, and air conditioning
in
inch/inches
MS4
municipal separate storm sewer
sq ft
square feet/foot
TMECC
Testing Methods for the Examination of Compost and Composting
USDA
U.S. Department of Agriculture
VFP
Veteran Farmer Project
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Executive Summary
The City of Albuquerque (City), working with private developer Geltmore, LLC and nonprofit housing
developer YES Housing, Inc., is engaged in a large multiuse redevelopment project on a 1-acre lot in its
downtown area. The Imperial Building will reclaim a former brownfield site and provide a wide range of
benefits to the community, including downtown Albuquerque's first grocery store, retail space, 74
residential units (which will provide both affordable and market rate housing), and operating space for a
local veterans group. As part of the project, the City wants to integrate green infrastructure into the site
design as an initial step towards incorporating those principles on a larger scale into the City's planning
and development process.
The primary goal of the project's green infrastructure elements is to capture stormwater and reuse it
on-site. Following a charrette held in June 2014, stakeholders decided to focus the design on the use of
a cistern. Specifically, rooftop runoff will be collected by the cistern and used to irrigate a rooftop
garden. Detailed designs were developed using climate data, an evaluation of irrigation demand, and
typical cistern operating conditions to calculate the appropriate cistern size.
Designs for ground-level bioretention planter boxes also were developed. Although initial plans for the
site included treatment of fugitive stormwater flows in the City's storm sewers and surface runoff to
irrigate landscaping around the base of the building, the final design did not include the fugitive flows
treatment because of cost concerns.
Groundbreaking for the project was held in January 2015, with an expected completion date of spring
2016.
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I. Introduction
The City of Albuquerque, New Mexico (City), lies within the northern edge of the Chihuahua Desert
ecoregion and is the most populous city in the state, with a population of 545,852 (AED 2016).
Several neighborhoods in downtown Albuquerque date back to the 1880s, when the transcontinental
railroad was established. Today, most of the neighborhoods are located in a flat river bottom and are
protected by levees, which create problems for storm drainage by blocking natural flow patterns.
Downtown Albuquerque has a significant homeless population, many of whom are veterans, as well as a
lack of fresh produce and grocery stores. This project (to redevelop a former brownfield site) aims to
mitigate the storm drainage problems by capturing stormwater and recycling it through an urban
garden, and providing locally produced food as well as therapeutic work for veterans. Through this
project, the City also hopes to integrate the concept of green infrastructure for future buildings and to
educate developers, engineers, and architects on the design principles. In addition, local students will be
able to learn through observation and documentation.
. • '' ¦ r Quality Issues/Goals
Albuquerque is located within the Middle Rio Grande watershed, which is listed as impaired for
Escherichia coli (E. coli). A total maximum daily load has been established to address that issue by
reducing E. coli loading by 66 percent. The climate of the watershed is arid with rainfall events that are
few and far between; the average annual rainfall for the area is approximately 9.5 inches (in) per year
(NOAA2013).
The U.S. Environmental Protection Agency (EPA) has assessed representative predevelopment hydrology
conditions for the Middle Rio Grande watershed (Tetra Tech 2014). On December 11, 2014, EPA issued a
general permit for municipal separate storm sewer system (MS4) dischargers in the Middle Rio Grande
watershed. The permit requires new development sites to manage on-site the 90th percentile storm
event, which approximates predevelopment hydrological conditions. Redevelopment sites must manage
on-site the 80th percentile storm event.
jject Overview and Goals
The Imperial Building project features a proposed 120,000-square-foot (-sq-ft) mixed-use (residential
and retail) building in downtown Albuquerque on Silver Avenue SW between 2nd Street SW and 3rd
Street SW (Figure 1-1). It is being undertaken by a public-private partnership between the City and UR
205 Silver, LLC, which is affiliated with Geltmore, LLC (the Developer). The Developer has designed a
5-story building that includes a 100-car below-ground parking garage, 23,000 sq ft of ground floor retail
space (including a grocery store), 74 apartments, and space for an urban vegetable garden on the roof
of the building (Figure 1-2).
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The Imperial Building Site
NAD_1927_Contiguous_USA_Albers
Map Produced 09-12-2014 - A Porteous
TETRA TECH
Meters
Source: Tetra Tech
Figure I-I, Location arid existing condition of the Imperial Building site.
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Source: Rendering by Dekker/Perich/Sabatini
Figure 1-2, Imperial Building: Perspective from 3rd Street.
The development site is a 0.97-acre tract of vacant land located on one-half of a city block that has been
designated by the federal government as a food desert—an area where affordable and nutritious food is
difficult to obtain, particularly for those without access to a car. One goal of this project is to change the
food desert into a sustainable development for the benefit of the entire community. By relocating an
existing urban farm and installing a stormwater capture system in the new development, the project will
support that goal.
The Veteran Farmer Project (VFP) is an existing urban agriculture program located across the street from
the project site. VFP is in need of a new location, as its lease on the current space expires soon. The
proposed development will include a new home for the VFP as a rooftop garden, creating another
connection to the healthy food movement. The Developer intends to use the stormwater runoff on-site
before releasing the flow into the storm drainage network, which can be a demonstration of green
infrastructure development in the Southwest.
The project includes an innovative water collection system that will recycle a portion of the annual
rainfall to water the garden on the roof of the structure. Originally, the project also included a design
element to capture some of the dry weather, or fugitive, flows in the storm drain system adjacent to the
property; however, Albuquerque Metropolitan Arroyo Flood Control Association (AMAFCA) ultimately
decided not to include that element in the project.1 To potentially serve other communities that might
1 AMAFCA is one of several entities involved in the design of the development and obtained green infrastructure technical
assistance for the project from the U.S. Environmental Protection Agency.
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be interested in including the fugitive flow capture element in their projects, this report contains the
conceptual designs for that element and presents them in section 3. The flows would have been treated
in a series of bioretention treatment planter boxes and then used to irrigate the street trees surrounding
the property and other ground-level site landscaping. The system also would have included a storage
tank with associated pumps, piping, drains, and controls.
: .... . , i:_
The proposed development will benefit a number of segments of the City's population and provide
benefits in many ways. Combining this development with best practices in stormwater management
furthers the interests of four public agencies tasked with working in public-private partnerships,
supports a project that will provide healthy foods to a low-income area, and stimulates economic
development. Some of the valuable outcomes the City hopes to foster include providing a positive
impact for veterans outside of the economic mainstream and teaching lower income children about
careers in green infrastructure and urban farming.2 Further, the City envisions this development as an
opportunity to make the area a community asset by using the roof of the building to improve the
walkability of the area (i.e., space currently dedicated to the VFP can be used for other purposes) and
using green building principles such as installing photovoltaic panels to power site lighting.
There is a tremendous amount of public support for this project in the community. The opening of a
grocery store in downtown Albuquerque was identified as a catalytic project in the Downtown 2010
Sector Development Plan, the planning document for the downtown area. The Mayor has made it a
priority of his administration, and the City has passed a resolution to authorize workforce housing funds
for the affordable housing component of the project. The County has passed an inducement resolution
to provide industrial revenue bonds to help finance the project, and the New Mexico Environment
Department is providing financing to help offset the cost of mitigating the loose soil and gas vapors on
the site that have made this property a brownfield. Making this development a demonstration project
for stormwater capture only furthers the efforts of all of these agencies who are working to make this
development a reality.
Students from ACE Leadership High School, a charter school that specializes in the fields of architecture,
construction, and engineering, will be included in the process, providing them with an opportunity to
learn about green infrastructure techniques and helping train the future work force to pursue careers in
this field. The City also will prepare a video handbook that captures the green infrastructure design
process at the early planning stage (and perhaps during the installation / implementation phase).
cal Challenges
A lack of knowledge about green infrastructure practices has been a concern of the development
community as the City implements the new MS4 permit. Through the very popular Imperial Building
project, AMAFCA hopes to provide leadership in implementing green infrastructure solutions and to use
the development as a demonstration project on incorporating the modern practices into new
development in the Southwest going forward.
2 The VFP has obtained a grant from the Veterans Administration.
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The City believes that techniques learned from this project will be copied by others in the community. It
is in discussions with the Developer about using the proposed growing bed technology developed for
this project on land owned by AMAFCA in other parts of the City that currently is sitting idle. Along with
additional fugitive water in the stormwater system, new parks and community gardens could be
developed and operated by the VFP to increase the amount of produce grown locally.
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2, Design Approach
On June 23-24, 2014, AMAFCA hosted a design charrette to bring together all of the professionals
involved in developing the Imperial Building project.
The intent of the design charrette was to discuss incorporating four main concepts into the site plan and
building design: rooftop urban agriculture, irrigation of the rooftop urban agriculture with rainwater
harvested from the rooftop, treating additional stormwater runoff on-site using green infrastructure
practices, and treating fugitive flows in an adjacent storm drain through a series of bioretention planter
boxes with irrigation of associated street trees. The charrette provided an opportunity for people with a
wide range of backgrounds (including architects, engineers, landscape architects, and flood control
experts) to team up and cooperate on the site plan.
The first day of the charrette began with an overview of green infrastructure concepts, including a brief
discussion of the impacts of development on the quantity and quality of stormwater runoff, site design
principles, and green infrastructure practices. The presentation included a brief discussion of how green
infrastructure concepts could be applied to the Imperial Building site, emphasizing the potential
configuration for bioretention areas, green roofs, and water harvesting systems. Students from ACE
Leadership High School also attended the presentation and participated in the discussion. The
remainder of the day was spent discussing the site configuration and constraints as well as general
concepts that could be applied at the site to meet treatment goals.
The second day focused on refining the site plan and developing as many details as possible for the
green infrastructure concepts to be implemented at the Imperial Building. Potential sources of runoff
were categorized as rooftop rainwater, fugitive or nuisance flows, ground-level runoff (e.g., from the
parking deck ramp), fire-test flow water, and condensate from the condenser units. It was determined
that the flows from testing the fire suppression system, condensate, and runoff from the rooftop would
be the cleanest sources of water from the site and would be harvested in a cistern. Nuisance flows and
runoff from the parking deck ramp could pick up pollutants and require substantial treatment before it
could be used within the building. That treatment could be cost-prohibitive and, therefore, those flows
will be treated and used to irrigate perennial landscape plantings (e.g., sidewalk trees), with the
remainder routed to the City's storm drainage network.
The information gathered at the charrette and the green infrastructure practice concepts were
integrated into the conceptual design for the Imperial Building site. It was determined in the charrette
that two design strategies would be incorporated into the site: water harvesting via cisterns and rain
barrels and bioretention planter boxes (which later were not adopted). Those two strategies are
described further below, with detailed design specifications provided in Appendices A and B.
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2.1. Cisterns and Rain Barrels
A cistern is an above-ground storage vessel with
either a manually operated valve or a
permanently open outlet (Figure 2-1 shows a rain
barrel, a small cistern). If the cistern has an
operable valve, the valve can be closed to store
stormwater for irrigation or infiltration between
storms. This system requires continual
monitoring by the resident or grounds crew, but
provides flexibility in water storage and metering.
If a cistern is provided with an operable valve and
water is stored inside for long periods, the cistern
must be covered to prevent mosquitoes from
breeding. A cistern system with a permanently
open outlet also can provide for metering
stormwater runoff. If the cistern outlet is
significantly smaller than the size of the downspout inlet (e.g., %- to Yi-in diameter), runoff will build up
inside the cistern during storms and will empty slowly after peak intensities subside. The cistern must be
designed and maintained to minimize clogging by leaves and other debris.
2.1.1. Hydrology
Cisterns are typically placed near roof downspouts so that flows from the downspouts can be easily
diverted into the cistern. Runoff enters the cistern near the top and is filtered to remove large sediment
and debris. Collected water exits the cistern from the bottom or can be pumped to areas more
conducive to infiltration. Cisterns can be used as a reservoir for temporary storage or as a flow-through
system for peak flow control. Each cistern is fitted with a valve that can hold the stormwater for reuse or
release the stormwater at a rate below the design storm rate. Regardless of the intent of the storage, an
overflow must be provided for times when the capacity of the cistern is exceeded. The overflow system
should convey the runoff away from structures, either routing the flow to a green infrastructure practice
for treatment or safely passing it into the stormwater drainage system. The volume of the cistern should
be allowed to slowly release, preferably into a green infrastructure practice for treatment or into a
landscaped area where infiltration has been enhanced.
Cisterns have been used for millennia to capture and store water. Droughts in recent years have
prompted a resurgence of rainwater harvesting technology as a means of offsetting potable water use.
Studies have shown that adequately designed and used systems reduce the demand for potable water
and can provide important hydrologic benefits (Vialle et ai. 2012; DeBusk et ai. 2012). Hydrologic
performance of rainwater harvesting practices varies with design and use; systems must be drained
between rain events to reduce the frequency of overflow (Jones and Hunt 2010). When a passive
drawdown system is included (e.g., an orifice that slowly bleeds water from the tank into an adjacent
vegetation bed or infiltrating practice), significant runoff reduction can be achieved (DeBusk et al. 2012).
2.1.2. Water Quality
Because most rainwater harvesting systems collect rooftop runoff, the water quality of runoff harvested
in cisterns is largely determined by surrounding environmental conditions (e.g., overhanging vegetation,
bird and wildlife activity, atmospheric deposition), roof material, and cistern material (Despins et al.
2009; Lee et al. 2012; Thomas and Greene 1993). Rooftop runoff tends to have relatively low levels of
Figure 2-1. Rain barrels at San Pasqual Academy,
Escondido, California.
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physical and chemical pollutants, but elevated microbial counts are typical (Gikas and Tsihrintzis 2012;
Lee et al. 2012; Lye 2009; Thomas and Greene 1993). Physicochemical contaminants can be further
reduced by implementing a first-flush diverter; however, such diverters generally have little impact on
reducing microbial counts (Lee et al. 2012; Gikas and Tsihrintzis 2012).
The pollutant reduction mechanisms of cisterns and rain barrels are not yet well understood, but
sedimentation and chemical transformations are thought to help improve water quality. Despite limited
data describing reduction in stormwater contaminant concentrations in cisterns, rainwater harvesting
can greatly reduce pollutant loads to waterways if stored rainwater is infiltrated into surrounding soils
using a low-flow drawdown configuration or when it is used for alternative purposes such as toilet
flushing or vehicle washing. Rainwater harvesting systems also can be equipped with filters to further
improve water quality
2.1.3. Applications
Cisterns come in a variety of sizes and configurations and can hold several hundred to several thousand
gallons (gal) of rainwater. Figure 2-2 shows a typical aboveground plastic cistern, and Figure 2-3 shows
the same cistern with a wooden wrap. Cisterns also can be decorative, such as the one shown in Figure
2-4 at the Children's Museum in Santa Fe, or can be placed below ground, as shown in Figure 2-5.
Smaller cisterns (fewer than 100 gal), or rain barrels, can be used on a residential scale (Figure 2-6).
Collected water can be used to supplement municipal water for nonpotable uses, primarily irrigation.
Although useful for meeting basic irrigation needs, rain barrels do not typically provide substantial
hydrologic benefits because they tend to be undersized relative to the size of the contributing drainage
area. Figure 2-7 shows rain barrels adequately sized for the contributing roof area.
Figure 2-2, Typical plastic cisterns.
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Figure 2-3. Wood wrapped cisterns.
Source: Santa Fe, New Mexico. Children's Museum
Figure 2-4. Decorative cistern.
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Figure 2-5. Below-grourid cistern.
Figure 2-6. Residential rain barrel
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Figure 2-7. Rain barrels adequately sized for contributing roof area.
2.2. Bioretention Planter Boxes
A bioretention planter box is typically a concrete
box containing soil media and vegetation that
functions like a small bioretention area but is
lined on the sides and might require an
underdrain (Figure 2-8). Bioretention treatment
planters are most often implemented along
paved streets, or around parking lots and
buildings to provide initial stormwater detention
and treatment of runoff. Such applications offer
an ideal opportunity to minimize directly
connected impervious expanses in highly
urbanized areas. In addition to stormwater
management benefits, flow-through planters
provide green space and improve natural aesthetics in tightly confined urban environments. Refer to
section 3 for vegetation specifications and to Appendix B for soil media details.
2.2.1. Hydrology
A planter box is a vegetated, landscaped (i.e., mulched or grassed) shallow depression that captures,
temporarily stores, and filters stormwater runoff before directing it toward a stormwater conveyance
system or other green infrastructure practice via underdrain pipes. The captured runoff infiltrates
through the bottom of the depression and an approximately 2-4-foot- (-ft-) deep soil media layer that
has an infiltration rate capable of draining the planter box (to the bottom of the soil media) within a
Figure 2-8. Bioretention planter box.
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specified design drawdown time (usually 48 hours). The soil media provide treatment through filtration,
adsorption, and biological uptake. Some volume reduction (15-20 percent) also is possible through
evapotranspiration (ET) and storage in the soil media (Hunt et al. 2006). Flow-through planters are
typically planted with grasses, shrubs, and trees that can withstand short periods of saturation (10-24
hours) followed by longer periods of drought. Flow-through planters are ideal for treating cistern
discharge if infiltration is restricted.
2.2.2. Water Quality
Planter boxes are typically volume-based green infrastructure practices intended primarily for water
quality treatment that also can provide some peak-flow and volume reduction. Planter boxes should be
used only in place of bioretention areas where geotechnical conditions do not allow for infiltration into
the subsoils. Although planter boxes do not allow for infiltration, they still provide functions considered
fundamental for green infrastructure practices and water quality treatment. They remove pollutants
through physical, chemical, and biological mechanisms. Similar to bioretention areas, they specifically
use sorption, microbial activity, plant uptake, sedimentation, and filtration. Planter boxes are capable of
consistent and high pollutant removal for sediment, metals, and organic pollutants (e.g., hydrocarbons).
Current research shows that pollutant removal is possible with underdrains through the function
provided at the surface and by the soil media. Table 2-1 reports the water quality performance of
bioretention planter boxes.
Table 2-1. Pollutant removal characteristics of bioretention planter boxes
Median Effluent
Minimum
Typical
Concentration
Recommended
Literature
(mg/L unless
Media Depth
Removal
otherwise
for T reatment
Pollutant
Efficiency
noted)
Removal Processes (ft)
References
Sediment
High
8.3
Settling in
pretreatment and
mulch layer, filtration
and sedimentation in
top 2-8 inches of
media.
1.5
Geosyntec and Wright
Water Engineers 2012;
Hatt et al. 2008; Hunt et
al. 2012; Li and Davis
2008; Stander and
Borst 2010
Metals
High
TCd: 0.94 pg/L
TCu: 7.67 pg/L
TPb: 2.53 pg/L
TZn: 18.3 pg/L
Removal with
sediment and sorption
to organic matter and
clay in media.
2
Geosyntec and Wright
Water Engineers 2012;
Hsieh and Davis 2005;
Hunt et al. 2012
Hydro-
carbons
High
N/A
Removal and
degradation in mulch
layer.
N/A
Hong et al. 2006; Hunt
et al. 2012
Total
Phosphorus
Medium
(-240-99%)
0.09
Settling with sediment,
sorption to organic
matter and clay in
media, and plant
uptake. Poor removal
efficiency can result
from media containing
high organic matter or
with high background
concentrations of
phosphorus.
2
Clark and Pitt 2009;
Davis 2007; Geosyntec
and Wright Water
Engineers 2012; Hsieh
and Davis 2005; Hunt
et al. 2006; Hunt and
Lord 2006; Li et al.
2010
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Pollutant
Typical
Literature
Removal
Efficiency
Median Effluent
Concentration
(mg/L unless
otherwise
noted)
Removal Processes
Minimum
Recommended
Media Depth
for T reatment
(ft)
References
Total
Nitrogen
Medium
(TKN: -5-
64%,
Nitrate:
180%)
TN: 0.90,
TKN: 0.60,
N02,3-N: 0.22
Sorption and settling
(TKN), denitrification
in internal water
storage (nitrate), and
plant uptake. Poor
removal efficiency can
result from media
containing high
organic matter.
3
Barrett et al. 2013;
Clark and Pitt 2009;
Geosyntec and Wright
Water Engineers 2012;
Hunt et al. 2006; Hunt
etal. 2012; Kimetal.
2003; Li etal. 2010;
Passeport et al. 2009
Bacteria
High
Enterococcus'.
234 MPN/100
mL, E.coli: 44
MPN/100 mL
Sedimentation,
filtration, sorption,
desiccation, predation,
and photolysis in
mulch layer and
media.
2
Geosyntec and Wright
Water Engineers 2012;
Hathaway et al. 2009;
Hathaway et al. 2011;
Hunt and Lord 2006;
Hunt etal. 2008; Hunt
et al. 2012; Jones and
Hunt 2010
Thermal
Load
High
68-75 °F
Heat transfer at depth
and thermal load
reduction by volume
reduction (ET and
infiltration). Internal
water storage
enhances thermal
load reduction.
4
Hunt et al. 2012; Jones
and Hunt 2009; Jones
et al. 2012; Wardynski
et al. 2013; Winston et
al. 2011
Notes', ft = feet; mg/L = milligram per liter; |jg/L = microgram per liter; mL = milliliter; MPN = most probable number; N023-N = Nitrate
and Nitrite Nitrogen; TCd = total cadmium; TCu = total copper; TKN = total Kjehldahl nitrogen; TN = total nitrogen; TPb = total lead;
TZn = total zinc
14
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2.2.3. Applications
Planter boxes can be implemented in situations in which infiltrating bioretention is not feasible,
including areas near buildings or in rights-of-way when utility conflicts restrict infiltration (Figure
Figure 2-9. Roadside flow-through planter.
15
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3. Conceptual Design
The Developer has designed a 5-story building that includes a parking basement, retail space, residential
units, and a rooftop urban garden. The site will be excavated approximately 12 feet below the existing
surface to provide structural support and to ensure that the parking garage is appropriately sealed. The
excavation will extend into the right-of-way to the back of the existing curb along 3rd Street SW, Silver
Avenue SW, and 2nd Street SW.
Approximately 4,000 sq ft of the rooftop is intended as a patio for use by the residents and an urban
farm that will be managed by the La Montanita Co-Op. An existing urban farm is currently located on a
site immediately adjacent to the Imperial Building site, as shown in Figure 3-1. Much of the remaining
rooftop space will be used for condenser units for climate control of the building. The grocery store roof
cannot be used at this time but could potentially be incorporated for residential use or urban farming
depending on the agreements made with the future tenant.
A 60-in diameter reinforced concrete pipe storm drain flows under 3rd Street SW on the west side of the
Imperial Building site. According to AMAFCA, a consistent flow of approximately 0.02 cubic feet per
second (cfs), or 8 gallons per minute (gpm), has recently been measured in through pipe. These flows
are considered fugitive, or nuisance, flows thought to be generated by activities of the residents and City
staff that include car washing, overirrigation, sidewalk scrubbing, street sweeping, and heating,
ventilation, and air conditioning (HVAC) condensate discharge. Some of the fugitive flows also could
consist of groundwater entering the storm drainage network through leaks in the pipes. The quality of
the fugitive flows is thought be relatively good; however, concerns about potential contaminants
currently precludes its use in the interior of the building or for spray irrigation.
Figure 3-1. Existing urban farm at 2nd Street and Gold Avenue SW.
16
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This project aims to mitigate the impacts of on-site stormwater runoff by capturing the water from the
rooftop areas and recycling it through an urban garden, to provide locally produced food and
therapeutic work for veterans, and to set an example for developers of similar buildings to be built in
the future. Stormwater runoff from the street level, including the parking ramp and the sidewalks along
the building frontage, would have been treated in a series of planter boxes along 2nd Street SW, Silver
Avenue SW, and 3rd Street SW. Through this project, the City hopes to educate (1) other developers on
the use of green infrastructure, (2) engineers and architects on the design concepts, (3) students
through observation and documentation, and (4) veterans through implementing the urban garden for
therapy, sustenance, and survival.
Additionally, AMAFCA has an interest in using redevelopment sites located throughout the City as areas
for treating nuisance water flows and providing incentives to developers (e.g., credits) who incorporate
on-site treatment of nuisance flows into their projects.
r ' ' .rtment Strategy
The schematic in Figure 3-2 summarizes the potential sources of water, potential reuse opportunities,
and the proposed integrated water reuse and treatment concept for the Imperial Building. Several
sources of water were targeted for treatment and reuse at the Imperial Building site. Since each source
has different water quality characteristics, a fit-for-purpose strategy was used to match each source
with an appropriate treatment method and end use.
• Rainfall runoff from 30,000 sq ft of rooftop
• Dry-weather nuisance flows from adjacent storm sewer (approximately 0.02 cfs, or 8 gpm,
continuous flow in pipe)
• Ground-level on-site runoff from the parking area, courtyard, pedestrian access paths, and
building frontage
• Fire-test flows (approx. 1,000 gal per year)
• HVAC condensate
17
-------
Rooftop Runoff
(~145,600 gal/yr.)
24,000 gal
Cistern
HVAC
Condensate
Fire-Test
Flows
Bioretention Planter Treated
Boxes
12.000 pat
Ground-level Runoff
Overflow
Dry Weather
"Nuisance Flows
Diversion
Pump
Storm Sewer
Perennial
Landscaping
Pretreatment
Settling Tank
Rooftop
Vegetable/Herb
Garden
Figure 3-2. Flow diagram for water reuse strategy at Imperial Building.
Runoff from the building's roof and the fugitive flows in the storm sewer are the focus of the green
infrastructure design. The design for the runoff also will account for HVAC and fire-test flows, while the
design for the fugitive flows also would have incorporated flow volumes from ground-level runoff.
3.2. Treatment of Rooftop Runoff
The source of the cleanest urban stormwater runoff is typically rooftops. Access to open space for
storing stormwater runoff in the soil or a reservoir, however, can be limited in higher density landscapes
like downtown Albuquerque. As a result, aboveground or belowground cisterns become viable options
for preserving the quality of rooftop runoff and storing it for subsequent irrigation of higher value food
crops. Annual vegetables, commercial mushroom operations, and aquaponic or hydroponic systems—all
of which require a relatively clean and constant water supply—are ideal uses for cistern water. From a
stormwater management perspective, these proposed revenue-generating, beneficial end uses establish
a reliable incentive for implementing stormwater volume and pollutant load reductions.
The runoff from the rooftop, as well as intermittent discharges from HVAC condensate and fire-testing,
will be harvested by being conveyed directly to a 24,000-gal cistern after coarse filtration and first-flush
diversion treatment of the rooftop runoff. A back-up municipal water supply should be connected to the
cistern to ensure irrigation water during extreme dry periods. The cistern also will include an overflow
pipe that discharges into the adjacent storm sewer. Cisterns are most effective for stormwater
treatment when adequate storage volume is available. A full water balance was performed to determine
the irrigation demand and to ensure that the cistern will be empty at the start of a rain event.
18
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3.2.1. Irrigation Demand
Initially, potential irrigation demands for the rooftop garden were calculated using local ET rates, typical
crop demands, irrigation system efficiencies, soil texture, plant available water, and other factors
associated with the proposed planter box system for the rooftop. These irrigation rates, however,
appeared much lower than those reported by existing urban farm sites and other local produce growers,
all of whom use similar drip irrigation products and timing schedules for their production. As a result, a
conservative approach was ultimately used that assumes set monthly irrigation durations (based on the
schedules currently used by local growers) and a 12-month production season. The calculated monthly
irrigation demands in Table 3-1 are based on a drip system with 8-in emitter spacing, 0.5-gal per hour
emitter rates, and three drip lines per 3-4-ft bed.
Table 3-1. Typical irrigation demands for vegetable production in Albuquerque
Month
Irrigated Minutes/Day
Gal/Day-100 sq ft
January
20
40
February
20
40
March
20
40
April
20
40
May
30
60
June
40
80
July
40
80
August
40
80
September
30
60
October
20
40
November
20
40
December
20
40
As currently proposed, the rooftop garden will include a minimum 810 sq ft of planter boxes. Based on
the assumed irrigation schedule described in Table 3-1, the annual irrigation demand for the garden is
approximately 72,500 gal.
3.2.2. Water Balance Modeling
The Rainwater Harvester (RH) model (Jones and Hunt 2010) simulates the performance of rainwater
harvesting systems using historical precipitation data to evaluate a daily or hourly water balance. The
model includes options for daily and hourly rainfall input files, customized water demand inputs,
automatic irrigation demand calculations, payback period costs, annual nitrogen reductions, and various
hydrologic performance output metrics.
Several input scenarios were modeled for this project to evaluate the performance of the Imperial
Building rainwater harvesting system in offsetting the rooftop garden irrigation demand; the results are
shown in Table 3-2. Two cistern sizes—24,000 gal and 36,000 gal—were selected based on the 100-year,
6-hour peak flood detention requirement. The 24,000-gal cistern assumes that the 12,000-gal water
quality volume for the site will be mitigated through capture and treatment of the ground-level runoff
using the roadside planter boxes. The 36,000-gal cistern scenario was modeled to evaluate the
hydrologic benefits of maximizing the cistern capacity on the site.
19
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Table 3-2. Cistern performance results
Cistern Size
(gai)
Rainfall Record
Annual Usage
(gai)
Irrigation Offset
(%)
Overflow
Frequency
(%)
Dry Frequency
(%)
24,000
5/2003-4/2013
59,247
95
38
4
24,000
6/2009-4/2013
59,001
94
24
4
36,000
5/2003-4/2013
60,185
98
37
2
36,000
6/2009-4/2013
60,614
98
21
1
The cistern will be located in the lower-level parking garage as shown in the site plan in Appendix A.
Planning level costs for treating the rooftop runoff are shown in Table 3-3.
Table 3-3. Cistern costs
Item No.
Description
Quantity
Unit
Unit Cost
Total
1
Excavation
133.3
CY
$8.50
$1,133
2
6-in gravel bedding layer
8.2
CY
$30.34
$248
3
24,000-gal storage tank
1.0
EA
$37,906.25
$37,906
4
Pump system
1.0
EA
$8,971.43
$8,971
5
Filter package
1.0
EA
$1,847.29
$1,847
6
Filter assembly
1.0
LS
$2,744.43
$2,744
Total Cistern Cost
$52,851
Notes'. CY = cubic yards; EA = each; LS = Lump sum.
3.3. Fugitive Flow Treatment
If AMAFCA had decided to include the fugitive flow treatment system in the Imperial Building project,
runoff from the parking deck ramp and the fugitive flows from AMAFCA's adjacent storm sewer would
have been routed through a pretreatment system installed at 3rd Street SW and the alley between
Silver Avenue SW and Gold Avenue SW. The flows would have passed through a primary treatment and
effluent distribution system installed under the sidewalks along 2nd Street SW, Silver Avenue SW, and
3rd Street SW, providing treatment as well as a consistent irrigation source for the required street trees.
Figure 3-3 shows the potential routing and treatment of the flows.
20
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Potential Routing and
Treatment of Fugitive Flows
NAD_1927_Contiguous_USA_Albers
Map Produced 09-12-2014 - A. Porteous
TETRA TECH
Meters
Figure 3-3. Potential routing and treatment of fugitive flows.
21
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Nuisance flows in the storm drain along 3rd Street SW would have been pumped directly into the
pretreatment system. Runoff from the parking deck would have been treated and stored in an oil/grit
separator and then transferred into the effluent dispersal/irrigation system. Primary treatment would
have been in a baffled tank, similar to a septic tank, with an effluent screen. There are a variety of
commercially available systems that could be used under the sidewalk to provide additional storage,
including a tree filter system with suspended pavement. The typical planter box configuration
recommended for implementation along 3rd Street SW, Silver Avenue SW, and 2nd Street SW is shown
in Figure 3-4.
3" TEMPORARY PONDING
UNDISTURBED
SOIL
12" WASHED NO.8 DRAINAGE
STONE W/UNDERDRAIN
12"-WIDE PEDESTRIAN
LANDING STRIP
NEW OR EXISTING
CURB
NEW SIDEWALK
DISTURBED
SOIL
13" LANDSCAPE GRAVEL OR COBBLE
6" WASHED #57 STONE
W/ SLEEVED PVC
DISTRIBUTION PIPES
24" BIORETENTION
SOIL MEDIA
2" WASHED ASTMC-33
CONCRETE SAND
30 MIL PLASTIC LINER ALONG BOTTOM
Figure 3-4. Typical bioretention planter box configuration.
Three treatment scenarios were developed to demonstrate increasing levels of treatment in the
bioretention areas along 2nd Street SW, Silver Avenue SW, and 3rd Street SW. The first treatment
scenario is the minimum bioretention area required to treat the runoff produced by the 0.44-in event at
the site, along with a corresponding amount of fugitive flow treatment during dry weather. The second
and third treatment scenarios each covers an increasingly larger treatment area intended to provide
additional treatment capacity for fugitive flows. Each treatment scenario includes capturing the runoff
from the parking ramp in a tank at the base of the ramp (shown in Figure 3-5) and then pumping the
flows to an irrigation dosing tank below the sidewalk on 3rd Street SW, as shown in Figure 3-6. The full
site plan is provided in Appendix A.
22
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MANHOLE RING WITH COVER
MANHOLE RING WITH GRATE
GRADE AT BOTTOM OF PARKING
RAMP, SLOPED TO GRATE
TOP OF MANHOLE
ELEV, 90'-0"
TOP OF TANK
ELEV. 89'-0"
1 r
1" PVC OUTLET PIPE TO
DISTRIBUTION PUMP BASIN
TRANSFER PUMP ON
ELEV. 83'-6" «
DIVERSION OFF
ELEV, 83'-0"
U sz
FLOAT OFF
ELEV. 82'-6"
I
TANK BOTTOM.
ELEV. 81'-0"
(1) 3/10 HP LOW-FLOW TRANSFER PUMP
FLOW: 2 GPM
TDH: 15.5'
SECTION VIEW
Figure 3-5. Tank to collect ramp runoff.
OVERFLOW PIPE TO
SHALLOW DRY WELL W/ EXISTING STORM SEWER
DIVERSION HUMP
(SUPPLIED BY AMAFCA)
(SIZE TBD)
INTAKE PIPE FROM EXISTING
60" RCP STORM SEWER
(13.2' DBG)
(2) 1500 GAL PRIMARY
SETTLING TANKS IN SERIES,
4' DIA. X 16' L
PRIMARY DOSING TANK W/
SIMPLEX PUMP SYSTEM
6' DIA. X 8'H
(SEE DETAIL 3.1, SHEET C3)
-3500 GAL SAND/OIL INTERCEPTOR
W/ SUMP TRANSFER PUMP
(SEE DETAIL 2.2, SHEET C3)
4" PVC OVERFLOW
PIPE TO EXISTING
STORM SEWER-
=H" SCH 40 PVC
s TRANSFER PIPE
(2) 3'-WIDE TREATMENT PLANTER BOXES
W/ UNDERDRAIN, VARIABLE LENGTH,
2' MEDIA DEPTH-
Figure 3-6. Routing of ramp stormwater runoff.
As noted above, AMAFCA ultimately decided not to include the fugitive flow treatment as part of the
final design plan for the Imperial Building site. The conceptual design is a viable design option, however,
and might be relevant to efforts in other communities and was, therefore, included in the proposed
conceptual design.
23
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3.3.1. Treatment Scenario I
A treatment planter box system with a minimum surface area of 775 sq ft is required to treat the 0.44-in
water quality event from the parking deck ramp and the sidewalk in front of the Imperial Building. The
planter box system will be dosed with runoff from the parking ramp at a rate of 1,550 gallons per day
(gpd). Fugitive flows can be applied to the system at the same rate when it is not raining, A cross section
of the planter box system is shown in Figure 3-7. Full plan details are included in Appendix A.
Specifications for the bioretention soil media are included in Appendix B.
MIN 3"
PONDING
VERTICAL SIDE WALLS FLUSH
WITH SIDEWALK EDGE.
VERTICAL REINFORCING @ 18"
MAX. FOR HORIZONTAL
REINFORCING, SEE DETAIL.
6" DIA PERFORATED PVC
(PERFORATIONS POINTED DOWN)
BOTTOM SLOPE 0.5%.
INSTALL 30 MIL PLASTIC LINER
1-WIDE PEDESTRIAN LANDING
STRIP ALONG PARKING LANE
3" LANDSCAPING STONE
SIDEWALK
2" WASHED ASTM C-33
CONCRETE SAND OVER 2"
NO. 8 STONE
WASHED NO. 57 DRAINAGE STONE
COMPACTED TO BE FIRM AND
UNYIELDING
(2) li" LOW PRESSURE SCH 40
DISTRIBUTION PIPES, SLEEVED WITHIN
4" SCH 40 PERFORATED PVC PIPE
WASHED NO. 57 DRAINAGE STONE
BIORETENTION SOIL MEDIA
(80% REL. COMPACTION)
DETAIL 1.1 - PLANTER BOX SECTION
Figure 3-7. Treatment planter box.
Planning level cost estimates for Treatment Scenario 1 are provided in Table 3-4.
Table 3-4. Ground-level runoff and nuisance flow treatment construction cost (Treatment Scenario I)
Item No.
Description
Quantity
Unit
Unit Cost
Total
Nuisance Flow Treatment
1
8,000-gal fiberglass settling tank
(6-ffc dia, 40-ft length)
1.0
EA
$22,000.00
$22,000
2
Bedding and backfill
1.0
LS
$0
3
Distribution pump system (pump,
control, floats)
10
LS
$1,000.00
$1,000
4
Pump basin
1.0
LS
$1,200.00
$1,200
5
4-in Schedule 40 PVC pipe
258.5
LF
$9.15
$2,365
6
3-in Schedule 40 PVC pipe
90.0
LF
$6.60
$594
7
2~in Schedule 40 PVC pipe
106.5
LF
$3.33
$355
24
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Item No.
Description
Quantity
Unit
Unit Cost
Total
8
1.5-in Schedule 40 PVC pipe
45.0
LF
$2.73
$123
9
1.25-in distribution line
513.3
LF
$3.30
$1,694
Total Nuisance Flow Treatment
$29,331
Parking Ramp Treatment
10
3,500-gal sand/oil interceptor
1.0
LS
$7,000.00
$7,000
11
Ring and cover
1.0
EA
$330.00
$330
12
Ring and grate
1.0
EA
$350.00
$350
13
Excavation
30.3
CY
$7.00
$212
14
Transfer pump system (pump,
screens, controls)
1.0
LS
$600.00
$600
Total Parking Ramp Treatment
$8,492
Planter Boxes
15
Hydraulic restriction layer
(6-in concrete)
2,650.0
sq ft
$16.00
$42,400
16
Bioretention media
72.6
CY
$40.00
$2,904
17
No. 8 stone
4.8
CY
$26.00
$124
18
Washed ASTM C-33 concrete sand
9.5
CY
$30.00
$285
19
Drainage stone (washed no. 57 stone)
40.9
CY
$45.00
$1,841
20
6-in Schedule 40 perforated PVC pipe
256.7
LF
$30.00
$7,700
21
6-in Schedule 40 PVC pipe
294.3
LF
$35.00
$10,302
22
6-in Schedule 40 perforated PVC pipe
cleanout
11.0
EA
$100.00
$1,100
23
Hydraulic restriction layer (30-mil liner)
3,420.0
sq ft
$0.50
$1,710
Total Planter Boxes
$68,365
Earthwork
24
Fill
38.0
CY
$8.50
$323
25
Pipe backfill and bedding
20.8
CY
$46.95
$976
26
Finish grading
7.8
SY
$0.17
$1
Total Earthwork
$1,300
Landscaping
27
Bioretention planting
770.0
sq ft
$1.00
$770
28
Landscaping rock
7.1
CY
$60.00
$428
Total Landscaping
$1,198
Electrical Control Integration
29
Electrical control integration
1
EA
$3,000
$3,000
Total Electrical Control Integration
$3,000
Construction Subtotal
$112,030
Mobilization and Stakeout 5%
$5,601
Bonds and Insurance 5%
$5,601
Construction Contingency 20%
$22,406
Total Construction Cost
$145,638
Notes'. CY = cubic yards; EA = each; LF = linear feet; LS = lump sum; PVC = polyvinyl chloride; SY = square yards.
25
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3.3.2. Treatment Scenario 2
The maximum area available for planter boxes is 1,320 sq ft along 2nd Street SW, Silver Avenue SW, and
3rd Street SW using the cross section shown in Figure 3-7 and increasing the length. Increasing the area
by 545 sq ft above the Treatment Scenario 1 treatment area allows for 2,640 gpd to be applied to the
planter boxes, an increase of 1,090 gpd. Adding the additional treatment capacity increases the
projected costs by approximately $46,000 compared to Treatment Scenario 1, as shown in Table 3-5.
Table 3-5. Ground-level runoff and nuisance flow treatment construction cost (Treatment Scenario 2)
Item No.
Description
Quantity
Unit
Unit Cost
Total
Nuisance Flow Treatment
1
8,000-gal fiberglass settling tank
(6-ft dia, 40-ft length)
1.0
EA
$22,000.00
$22,000
2
Bedding and backfill
1.0
LS
$0
3
Distribution pump system (pump,
control, floats)
1.0
LS
$1,000.00
$1,000
4
Pump basin
1.0
LS
$1,200.00
$1,200
5
4-in Schedule 40 PVC pipe
258.5
LF
$9.15
$2,365
6
3-in Schedule 40 PVC pipe
90.0
LF
$6.60
$594
7
2-in Schedule 40 PVC pipe
106.5
LF
$3.33
$355
8
1.5-in Schedule 40 PVC pipe
45.0
LF
$2.73
$123
9
1.25-in distribution line
880.0
LF
$3.30
$2,904
Total Nuisance Flow Treatment
$30,541
Parking Ramp Treatment
10
3,500-gal sand/oil interceptor
1.0
LS
$7,000.00
$7,000
11
Ring and cover
1.0
EA
$330.00
$330
12
Ring and grate
1.0
EA
$350.00
$350
13
Excavation
30.3
CY
$7.00
$212
14
Transfer pump system (pump,
screens, controls)
1.0
LS
$600.00
$600
Total Parking Ramp Treatment
$8,492
Planter Boxes
15
Hydraulic restriction layer
(6-in concrete)
4,500.0
sq ft
$16.00
$72,000
16
Bioretention media
124.4
CY
$40.00
$4,978
17
No. 8 stone
8.1
CY
$26.00
$212
18
Washed ASTM C-33 concrete sand
16.3
CY
$30.00
$489
19
Drainage stone (washed no. 57
stone)
70.1
CY
$45.00
$3,156
20
6-in Schedule 40 perforated PVC
pipe
440.0
LF
$30.00
$13,200
21
6-in Schedule 40 PVC pipe
111.0
LF
$35.00
$3,885
22
6-in Schedule 40 perforated PVC
pipe cleanout
11.0
EA
$100.00
$1,100
23
Hydraulic restriction layer (30-mil
liner)
5,820.0
sq ft
$0.50
$2,910
Total Planter Boxes
$101,930
26
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item No.
Description
Quantity
Unit
Unit Cost
Total
Earthwork
24
Fill
38.0
CY
$8.50
$323
25
Pipe backfill and bedding
20.8
CY
$46.95
$976
Finish grading
13.3
SY
$0.17
$2
Total Earthwork
$1,301
Landscaping
26
Bioretention planting
1,320.0
sq ft
$1.00
$1,320
27
Landscaping rock
12.2
CY
$60.00
$733
Total Landscaping
$2,053
Electrical Control Integration
28
Electrical control integration
1
EA
$3,000
$3,000
Total Electrical/Controls
$3,000
Construction Subtotal
$147,906
Mobilization and Stakeout 5%
$7,395
Bonds and Insurance 5%
$7,395
Construction Contingency 20%
$29,581
Total Construction Cost
$192,278
Notes'. CY = cubic yards; EA = each; LF = linear feet; LS = lump sum; PVC = polyvinyl chloride; SY = square yards.
3.3.3. Treatment Scenario 3
To maximize the treatment potential at the site, a suspended pavement system could be implemented
under the sidewalk adjacent to the planter boxes, as shown in Figure 3-8.
ROOT BARRIER
HYDRAULIC RESTRICTION LAYER
(30 MIL PVC LINER)
SUSPENDED PAVEMENT SYSTEM,
UNIT DIMENSION: 48"LX 24"WX 16" H,
2 UNITS STACKED
EXISTING
ROADWAY
75 UM (NO. 200) 0 TO 2%,
VALUE MUST BE OBTAINED BY WASHING
WASHED NO. 57 DRAINAGE STONE
WASHED NO. 57 DRAINAGE STONE
COMPACTED TO BE FIRM AND
UNYIELDING
VERTICAL SIDE WALLS. VERTICAL
REINFORCING @ 18" MAX. FOR
HORIZONTAL REINFORCING, SEE
TABLE 1.
6" DIA PERFORATED PVC
(PERFORATIONS POINTED DOWN)
BIORETENTION SOIL MEDIA
(80% REL. COMPACTION)
2" WASHED ASTM C-33
CONCRETE SAND OVER
DRAINAGE LAYER
BOTTOM SLOPE 0.5%.
INSTALL 30 MIL PLASTIC
LINER
APPROX. EDGE OF BUILDING
(2) 1 J" LOW PRESSURE SCH 40
DISTRIBUTION PIPES, SLEEVED WITHIN
4" SCH 40 PERFORATED PVC PIPE
Figure 3-8. Planter boxes with a suspended pavement system.
27
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Adding the suspended pavement system increases the surface area of the treatment system, allowing
treatment of 4,400 gpd, an increase of 1,760 gpd above Treatment Scenario 2 and 2,850 gpd above
Treatment Scenario 1. Adding the additional treatment capacity increases the projected costs by
approximately $30,000 compared to Treatment Scenario 2 and approximately $77,000 compared to
Treatment Scenario 3, as shown in Table 3-6.
Table 3-6. Ground-level runoff and nuisance flow treatment construction cost (Treatment Scenario 3)
Item No.
Description
Quantity
Unit
Unit Cost
Total
Nuisance Flow Treatment
1
8,000-gal fiberglass settling tank
(6-ft dia, 40-ft length)
1.0
EA
$22,000.00
$22,000
2
Bedding and backfill
1.0
LS
$0
3
Distribution pump system (pump,
control, floats)
1.0
LS
$1,000.00
$1,000
4
Pump basin
1.0
LS
$1,200.00
$1,200
5
4-in Schedule 40 PVC pipe
258.5
LF
$9.15
$2,365
6
3-in Schedule 40 PVC pipe
90.0
LF
$6.60
$594
7
2-in Schedule 40 PVC pipe
106.5
LF
$3.33
$355
8
1.5-in Schedule 40 PVC pipe
45.0
LF
$2.73
$123
9
1.25-in distribution line
1,320.0
LF
$3.30
$4,356
Total Nuisance Flow Treatment
$31,993
Parking Ramp Treatment
10
3,200-gal sand/oil interceptor
1.0
LS
$6,038.00
$6,038
11
Ring and cover
1.0
EA
$330.00
$330
12
Ring and grate
1.0
EA
$350.00
$350
13
Excavation
30.3
CY
$7.00
$212
14
Transfer pump system (pump, screens,
controls)
1.0
LS
$600.00
$600
Total Parking Ramp Treatment
$7,530
Planter Boxes
15
Hydraulic restriction layer
(6-in concrete)
2,940.0
sq ft
$16.00
$47,040
16
Bioretention media
124.4
CY
$40.00
$4,978
17
No. 8 stone
8.1
CY
$26.00
$212
18
Washed ASTM C-33 concrete sand
16.3
CY
$30.00
$489
19
Drainage stone (washed no. 57 stone)
70.1
CY
$45.00
$3,156
20
6-in Schedule 40 perforated PVC pipe
440.0
LF
$30.00
$13,200
21
6-in Schedule 40 PVC pipe
111.0
LF
$35.00
$3,885
22
6-in Schedule 40 perforated PVC pipe
cleanout
11.0
EA
$100.00
$1,100
23
Hydraulic restriction layer (30-mil liner)
5,820.0
sq ft
$0.50
$2,910
24
Suspended pavement system
880.0
sq ft
$53.00
$46,640
Total Planter Boxes
$123,610
Earthwork
25
Fill
38.0
CY
$8.50
$323
26
Off-site hauling
173.0
CY
$12.00
$2,076
28
-------
Item No.
Description
Quantity
Unit
Unit Cost
Total
27
Pipe backfill and bedding
20.8
CY
$46.95
$976
28
Finish grading
13.3
SY
$0.17
$2
Total Earthwork
$3,377
Landscaping
29
Bioretention planting
1,320.0
sq ft
$1.00
$1,320
30
Landscaping rock
12.2
CY
$60.00
$733
Total Landscaping
$2,053
Electrical Control Integration
31
Electrical control integration
1
EA
$3,000
$3,000
Total Electrical/Controls
$3,000
Construction Subtotal
$171,105
Mobilization and Stakeout 5%
$8,555
Bonds and Insurance 5%
$8,555
Construction Contingency 20%
$34,221
Total Construction Cost
$222,437
Notes: CY =
cubic yards; EA = each; LF = linear feet; LS
= lump sum; PVC = polyvinyl chloride; SY
= square yards.
3.3.4. Summary
A comparison of the costs and treatment capacities for the three treatment scenarios is shown in
Table 3-7.
Table 3-7. Treatment Scenario comparison.
Element
Scenario 1
Scenario 2
Scenario 3
Treatment Area (sq ft)
775
1,320
2,200
Treatment Capacity (gpd)
1,550
2,640
4,400
Cost
$145,638
$192,278
$222,437
Site plans and details for each treatment scenario are included in Appendix A.
3.4. Planting Plan
For a green infrastructure practice to function properly as stormwater treatment and blend into the
landscape, vegetation selection is crucial. Appropriate vegetation will have the following characteristics:
• Tolerant of drought, ponding fluctuations, and saturated soil conditions for 10-48 hours.
• A combination of a minimum of three tree, three shrubs, and/or three herbaceous groundcover
species incorporated, where possible, to protect against facility failure from disease and insect
infestations of a single species.
• Native plant species or hardy cultivars that are not invasive and do not require chemical inputs
used to the maximum extent practicable.
The vegetation shown in Table 3-8 was recommended by the design team to fit the specific site
constraints.
29
-------
Table 3-8. Recommended vegetation
55 *
D U)
Plant Species Common Name IS'0
Acernegundo
Box Elder
30 ft x 20 ft
L
SU
D
Celtis occidentalis
Common Hackberry
60 ft x 60 ft
M
PS
D
Amelanchier arborea
Downy Serviceberry
20 ft x 20 ft
M
SU
D
Amelanchier canadensis
Shadblow Serviceberry
25 ft x 20 ft
M
SU
D
Sambucus
Elderberry
10 ft x 10 ft
M
SU
D
Aronia
Chokeberry
6 ft x 6 ft
M
SU
D
2 >.
i c
(D O
nts
e -SH
» "5 =
^ TO
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CO
0 32
-PS
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TO C
£ «
a) s q:
£ 5
£ en
1
0
-Q
Q
3 ¦
0
TO
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"O
JO
.2 1 _i
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w
TO 0)
0)"D .1
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3.5. Operation and Maintenance
General maintenance activities for cisterns and rain barrels are similar to the routine periodic
maintenance for on-site drinking water wells. The primary maintenance requirement is to inspect the
tank and distribution system and test any backflow-prevention devices. Rain barrels require minimal
maintenance several times a year and after major storms to prevent any clogging. Cisterns require
inspection for clogging and structural soundness twice a year, including inspection of all debris and
vector control screens. If a first-flush diverter is used, it should be dewatered and cleaned after each
significant storm event. Self-cleaning filters and screens, such as the ones shown in Figure 3-9, can help
prevent debris from entering the cistern and reduce maintenance. Accumulated sediment in the tank
must be removed at least once a year.
Figure 3-9. Self-cleaning inlet filters.
30
-------
Table 3-9 provides a detailed list of maintenance activities.
Table 3-9. Inspection and maintenance tasks for cisterns
Task
Frequency
Indicator That
Maintenance Is
Needed
Maintenance Notes
Inspect the gutter and
rooftop.
Biannually and
before heavy rains
Inlet is clogged with
debris
Clean gutters and roof of debris that
has accumulated; check for leaks.
Remove accumulated
debris.
Monthly
Inlet is clogged with
debris
Clean debris screen to allow
unobstructed stormwater flow into the
cistern.
Inspect the foundation.
Biannually
Cistern is leaning or
soils are slumping /
eroding
Check cistern for stability; anchor
system if necessary.
Inspect the structure.
Annually
Cistern leaks and is
slow draining
Check pipe, valve connections, and
backflow preventers for leaks; verify
that flows empty the structure within
24-48 hours.
Add ballast.
Before any major
wind-related storms
Tank is less than half
full
Add water to half full.
Perform miscellaneous
upkeep.
Annually
Make sure cistern manhole is
accessible, operational, and secure.
Maintenance activities for vegetated green infrastructure practices should be focused on the major
system components, especially landscaped areas. Landscaped components should blend over time
through plant and root growth and organic decomposition, and they should develop a natural soil
horizon. These biological and physical processes will lengthen the facility's life span and reduce the need
for extensive maintenance.
Irrigation might be needed, especially during plant establishment or periods of extended drought.
Irrigation frequency will depend on the season and type of vegetation. Native plants require less
irrigation than nonnative plants.
Table 3-10 outlines the required maintenance tasks, their associated frequency, and notes to expand on
the requirements of each task based on recommendations from researchers in the green infrastructure
field.
31
-------
Table 3-10. Inspection and maintenance tasks for bioretention planter box
Task
Frequency
Maintenance Notes
Monitor infiltration and
drainage.
Annually
Inspect drainage time (12-24 hours); might have to
determine the infiltration rate (every 2-3 years); turning
over or replacing media (top 2-3 in) might be necessary
to improve infiltration (at least 0.5 in per hour).
Prune the vegetation.
Annually
Nutrients in runoff often cause bioretention vegetation to
flourish.
Mulch the vegetation.
Annually
Recommend maintaining 1-3-in uniform mulch layer.
Remove mulch.
Every 3-4 years
Biodegraded mulch accumulation reduces available
water storage volume; removal of mulch also increases
surface infiltration rate of fill soil.
Water the vegetation.
1 time/2-3 days for first 1-2
months; sporadically after
establishment
If drought conditions exist, watering after the initial year
might be required.
Fertilize the vegetation.
1 time initially
One-time spot fertilization for first-year vegetation.
Remove and replace
dead plants.
Annually
It is common for 10% of plants to die during first year;
survival rates tend to increase with time.
Inspect the inlet.
Once after first rain of the
season, then monthly during
the rainy season
Check for sediment accumulation to ensure that flow
into the retention area is as designed; remove any
accumulated sediment.
Inspect the outlet.
Once after first rain of the
season, then monthly during
the rainy season
Check for erosion at the outlet and remove any
accumulated mulch or sediment.
Perform miscellaneous
upkeep.
Biannually
Includes trash collection, plant health, spot weeding,
and removing mulch from the overflow device.
32
-------
4. Conclusion
With the arid Southwest facing water supply challenges, innovative solutions are necessary to reduce
potable water demand. Methods to maximize the use of the limited rainfall that occurs in the region are
needed.
This project designed a water harvesting system to capture rooftop runoff and reuse it for irrigation on
the rooftop garden. The garden serves multiple purposes, including reducing rooftop temperatures and
stormwater runoff, and as an urban food source. The system can serve as a model for developments in
other Southwest communities.
A second component of the project, not included in the final design, was development of a system to
capture and treat fugitive flows from an adjacent storm sewer. Even during dry weather, storm sewers
can produce significant volumes of stormwater from excess irrigation runoff and other sources. A
system to capture and reuse these fugitive flows for irrigation would reduce potable water use.
Although challenging, systems to capture and use fugitive flows should be considered in future
developments where practical.
33
-------
5. References
AED (Albuquerque Economic Development). 2016. Demographics page.
h ttp://www. aba. ora/Demoaraohics. asox
Barrett, M.E., M. Limouzin, and D.F. Lawler. 2013. Effects of media and plant selection on biofiltration
performance. Journal of Environmental Engineering 139(4):462-470.
Clark, S.E., and R. Pitt. 2009. Storm-water filter media pollutant retention under aerobic versus
anaerobic conditions. Journal of Environmental Engineering 135(5):367-371.
Davis, A.P. 2007. Field performance of bioretention: Water quality. Environmental Engineering Science
24(8):1048-1063.
DeBusk, K.M., W.F. Hunt, M. Quigley, J. Jeray, and A. Bedig. 2012. Rainwater Harvesting: Integrating
Water Conservation and Stormwater Management through Innovative Technologies. In
Proceedings of the 2012 World Environmental & Water Resources Congress: Crossing
Boundaries, Environmental & Water Resources Institute and American Society of Civil Engineers,
Albuquerque, New Mexico, May 20-24, 2012, pp. 3703-3710.
Despins, C., K. Farahbakhsh, and C. Leidl. 2009. Assessment of rainwater quality from rainwater
harvesting systems in Ontario, Canada. Journal of Water Supply: Research and Technology—
AQUA 58(2):117-134.
Geosyntec and Wright Water Engineers (Geosyntec Consultants, Inc., and Wright Water Engineers, Inc.).
2012. International Stormwater Best Management Practices (BMP) Database Pollutant Category
Summary Statistical Addendum: TSS, Bacteria, Nutrients, and Metals. Prepared for American
Society of Civil Engineers/Environmental and Water Resources Institute, Federal Aviation
Administration, and Water Environment Research Foundation by Geosyntec Consultants, Inc.,
and Wright Water Engineers, Inc.
Gikas, G.D., and V. A. Tsihrintzis. 2012. Assessment of water quality of first-flush roof runoff and
harvested rainwater. Journal of Hydrology 466/467:115-126.
Hathaway, J.M., W.F. Hunt, and S.J. Jadlocki. 2009. Indicator bacteria removal in stormwater best
management practices in Charlotte, North Carolina. Journal of Environmental Engineering
135 (12): 1275-1285.
Hathaway, J.M., W.F. Hunt, A.K. Graves, and J.D. Wright. 2011. Field evaluation of bioretention indicator
bacteria sequestration in Wilmington, NC. Journal of Environmental Engineering 137(12):1103-
1113.
Hatt, B.E., T.D. Fletcher, and A. Deletic. 2008. Hydraulic and pollutant removal performance of fine
media stormwater filtration systems. Environmental Science & Technology 42(7):2535-2541.
Hong, E., M. Seagren, and A.P. Davis. 2006. Sustainable oil and grease removal from synthetic
stormwater runoff using bench-scale bioretention studies. Water Environment Research
78(2):141-155.
Hsieh, C.H., and A.P. Davis. 2005. Evaluation and optimization of bioretention media for treatment of
urban stormwater runoff. Journal of Environmental Engineering 131(11):1521-1531.
34
-------
Hunt, W.F., and W.G. Lord. 2006. Bioretention Performance, Design, Construction, and Maintenance.
North Carolina Cooperative Extension, Raleigh, NC.
Hunt, W.F., A.R. Jarrett, J.T. Smith, and L.J. Sharkey. 2006. Evaluating bioretention hydrology and
nutrient removal at three field sites in North Carolina. Journal of Irrigation and Drainage
Engineering 132(6):600-608.
Hunt, W.F., J.T. Smith, S.J. Jadlocki, J.M. Hathaway, and P.R. Eubanks. 2008. Pollutant removal and peak
flow mitigation by a bioretention cell in urban Charlotte, NC. Journal of Environmental
Engineering 134(5):403-408.
Hunt, W.F., A.P. Davis, and R.G. Traver. 2012. Meeting hydrologic and water quality goals through
targeted bioretention design. Journal of Environmental Engineering 138(6):698-707.
Jones, M.P., and W.F. Hunt. 2009. Bioretention impact on runoff temperature in trout sensitive waters.
Journal of Environmental Engineering 135(8):577-585.
Jones, M.P., and W.F. Hunt. 2010. Effect of stormwater wetlands and wet ponds on runoff temperature
in trout sensitive waters. Journal of Irrigation and Drainage Engineering 136(9):656-661.
Jones, M. P. and W. F. Hunt. 2010. Performance of rainwater harvesting systems in the
southeastern United States. Resour. Conserv. Recy. 54: 623-629.
Jones, M.P., W.F. Hunt, and R.J. Winston. 2012. Effect of urban catchment composition on runoff
temperature. Journal of Environmental Engineering 138(12):1231-1236.
Kim, H., E.A. Seagren, and A.P. Davis. 2003. Engineered bioretention for removal of nitrate from
stormwater runoff. Water Environment Research 75(4):355-367.
Lee, J.Y., G. Bak, and M. Han. 2012. Quality of roof-harvested rainwater—Comparison of different
roofing materials. Journal of Environmental Pollution 162(2012):422-429.
Li, H., and A.P. Davis. 2008. Urban particle capture in bioretention media. I: Laboratory and field studies.
Journal of Environmental Engineering 143(6):409-418.
Li, M.H., C.Y. Sung, M.H. Kim, and K.H. Chu. 2010. Bioretention for Stormwater Quality Improvements in
Texas: Pilot Experiments. Texas A&M University in cooperation with Texas Department of
Transportation and the Federal Highway Administration.
Lye, D.J. 2009. Rooftop runoff as a source of contamination: A review. Science of the Total Environment
407:5429-5434.
NOAA (National Oceanic and Atmospheric Administration). 2013. 2012 Weather Highlights-
Temperature and Precipitation: Albuquerque.
http://www.srh.noaa.aov/aba/?n=climonhiah2012annual~temaoreciDaba.
Passeport, E., W.F. Hunt, D.E. Line, R.A. Smith, and R.A. Brown. 2009. Field study of the ability of two
grassed bioretention cells to reduce stormwater runoff pollution. Journal of Irrigation and
Drainage Engineering 135(4):505-510.
Stander, E.K., and M. Borst. 2010. Hydraulic test of a bioretention media carbon amendment. Journal of
Hydrologic Engineering 15(6):531-536.
35
-------
Kosco, J., K. Alvi, and M. Faizullabhoy. 2014. Estimating Predevelopment Hydrology in the Middle Rio
Grande Watershed, New Mexico. EPA Publication Number 832-R-14-007. Prepared for U.S.
Environmental Protection Agency, Office of Wastewater Management, byTetraTech, Inc.,
Fairfax, VA.
Thomas, P.R., and G.R. Greene. 1993. Rainwater quality from different roof catchments. Water Science
28 (3-5): 291-299.
Vialle, C., C. Sablayrolles, M. Lovera, M.C. Huau, S. Jacob, and M. Montrejaud-Vignoles. 2012. Water
quality monitoring and hydraulic evaluation of a household roof runoff harvesting system in
France. Water Resource Management 26:2233-2241.
Wardynski, B.J., R.J. Winston, and W.F. Hunt. 2013. Internal water storage enhances exfiltration and
thermal load reduction from permeable pavement in the North Carolina mountains. Journal of
Environmental Engineering 139(2):187-195.
Winston, R.J., W.F. Hunt, and W.G. Lord. 2011. Thermal mitigation of urban stormwater by level
spreader—Vegetative filter strips. Journal of Environmental Engineering 137(8):707-716.
36
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Appendix A: Site Plan arid Details
A-l
-------
SHALLOW DRY WELL W/
DIVERSION PUMP
(SUPPLIED BY AMAFACA
INTAKE PIPE FROM EXISTING
60" RCP STORM SEWER
(13.2" DBG)
(2) 1500 GAL PRIMARY
SETTLING TANKS IN SERIES,
4' DIA. X 16" L
PRIMARY DOSING TANK W/
SIMPLEX PUMP SYSTEM
6' DIA. X 8'H
(SEE DETAIL 3.1, SHEET C3)
4" PVC OVERFLOW
PIPE TO EXISTING
STORM SEWER-
(2) 3-WIDE TREATMENT PLANTER BOXES
W/ UNDERDRAIN, VARIABLE LENGTH,
2' MEDIA DEPTI
OVERFLOW PIPE TO
EXISTING STORM SEWER
(SIZE TBD)
TO EXISTING 60" RCP
STORM SEWER
~~~
W/ SUMP TRANSFER PUMP
(SEE DETAIL 2.2, SHEET C3)
24000 GAL CISTERN
12 FT DIA X 30 FT L
EXACT LOCATION TBD
SCH 40 PVC
TRANSFER PIPE
ORCE MAIN/MANIFOLD,
SCH 40 PVC,
VARIABLE PIPE SIZES
(SEE TABLE 3, SHEET C3)
4 -WIDE PLANTER BOXES W/ UNDERDRAIN
VARIABLE WIDTH, 3' MEDIA DEPTH
DIA. PVC UNDERDRAIN
PERFORATIONS WITHIN
PLANTER BOX EXTENTS ONLY
LX SJ L/\J
--B-E
B-e
NOT TO SCALE
;4) 3'-WlDE PLANTER BOXES W/ UNDERDRAIN,
VARIABLE LENGTH, 2' MEDIA DEPTH
(SEE DETAIL 1.1, SHEET C2)
EE DETAIL 1.3, SHEET C2
X
u
111
I-
2
i,
NOT TO SCALE
~~ ~~ ~
~~ ~~ ~
~~ ~~ ~
PROPOSED PLANTER
BOX ALONG 3RD ST.,
2' MEDIA DEPTH
~ ~~~~~~~~~~~
~ ~~~~~~~~~~~
~ ~~~~~~~~~~~
—irj'-TTi?-®
IRRIGATION PUMP SYSTEM
CENTRIFUGAL PUMP
PRESSURE TANK
EFFLUENT FILTER
|2) 1500 GAL PRIMARY SETTLING
TANKS IN SERIES.
BOTTOM ELEV: 93-6" (LOWESTTANK)
(SEE DETAIL 2.1, SHEET C3)
24000 GAL CISTERN,
12' DIA, 4' SOIL COVER
BOTTOM ELEV. 73'-0"
SECTION VIEW
1200 GAL SAND/OIL
SEPARATOR WITH SUMP
PUMP SYSTEM
BOTTOM ELEV: 8r-0"
(SEE DETAIL 2.2, SHEET C3)
0
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LU
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PROJECT-NO
Designed By:
Drawn By:
Checked By:
C1
A-2
-------
BIORETENTION MEDIA SPECIFICATION
BSM
Composition
Sand
Sandy Loam
Compost
Sand I Silt I Clay
Volume
65%
20%
15%
Weight
75-80% | 10% max | 3% max.
9% max.'
NOT TO SCALE
compost by weight results in approximately 5% organic matter by weight.
VERTICAL SIDE WALLS FLUSH
WITH SIDEWALK EDGE.
VERTICAL REINFORCING @ 18"
MAX. FOR HORIZONTAL
REINFORCING, SEE DETAIL.
SIDEWALK
FORCE MAIN/MAINFOLD
(SEE TABLE 3, SHEET C3
FOR PIPE SIZE)
2" WASHED ASTM C-33
CONCRETE SAND OVER 2"
NO. 8 STONE
WASHED NO. 57 DRAINAGE STONE
COMPACTED TO BE FIRM AND
UNYIELDING
MIN 3
PONDING
KXXaXXXa
r-WIDE PEDESTRIAN LANDING
STRIP ALONG PARKING LANE
3" LANDSCAPING STONE
6" DIA PERFORATED PVC
(PERFORATIONS POINTED DOWN)
(2) li" LOW PRESSURE SCH 40
DISTRIBUTION PIPES, SLEEVED WITHIN
4" SLOTTED PERFORATED PLASTIC PIPE
6" LAYER WASHED NO. 57 DRAINAGE
STONE
BIORETENTION SOIL MEDIA
(80% REL. COMPACTION)
BOTTOM SLOPE 0.5%.
INSTALL 30 MIL PLASTIC LINER
DETAIL 1.1- (SECTION A-A) PLANTER BOX SECTION
NOT TO SCALE
(1)4" SLOTTED PERFORATED PLASTIC
PIPE, END FED BY J" SCH 80 PVC TAPS,
THREADED INTO 2" SUPPLY MANIFOLD.
FORCE MAIN/MAINFOLD
(SEE TABLE 3, SHEET C3
FOR PIPE SIZE)
HYDRAULIC RESTRICTION LAYER
(30 MIL PVC LINER)
SUSPENDED PAVEMENT SYSTEM,
UNIT DIMENSION: 48"L X 24"W X 16" H,
2 UNITS STACKED
ASTM C-33 SAND WITH ADDED PROVISION:
75 UM (NO. 200) 0 TO 2%,
VALUE MUST BE OBTAINED BY WASHING
(2) 1f LOW PRESSURE SCH 40
DISTRIBUTION PIPES, SLEEVED WITHIN
4" SLOTTED PERFORATED PLASTIC PIPE
ROOT BARRIER
EXISTING
ROADWAY
WASHED NO. 57 DRAINAGE STONE
jrir '"¦*!
VERTICAL SIDE WALLS. VERTICAL
REINFORCING @ 18" MAX. FOR
.v : HORIZONTAL REINFORCING, SEE
\ TABLE!
BIORETENTION SOIL MEDIA
(80% REL. COMPACTION)
BOTTOM SLOPE 0.5%.
INSTALL 30 MIL PLASTIC
LINER
DETAIL 1.2 - SCENARIO 3 PLANTER BOX SECTION
W/ SUSPENDED PAVING TREATMENT
IMPERIAL BUILDING
CONCRETE SIDEWALK
(SLOPED TO PLANTER BOX)
ORCE MAIN/MAM FOLD
FLOW
FLOW
FLOW
FLOW
2" SCH 40 PVC
SUPPLY MANIFOLD
7AV/*®:
2" GLOBE OR GATE
VALVE FOR PRESSURE
ADJUSTMENT
—— ^
— ¦ —
222k
3~=T-Z3
m®: ..; :-%m.
/^A/yK'x/yxx/.
DIA PERFORATED
PVC UNDERDRAIN
-1' WIDE CONCRETE PEDESTRIAN
LANDING STRIP ALONG PARKING
LANE
-(2) CLEANOUTS AND PRESSURE CHECK PORTS
WITH TURN-UPS AND SCREW CAP ENDS
~(2) 1|" LOW PRESSURE
DISTRIBUTION PIPE,
40' LENGTH W/^" HOLES
DRILLED 5' OC, STAGGERED
BETWEEN LINES.
ALL HOLES POINTING UP
EXCEPT ONE HOLE FOR
DRAINAGE
DIA SOLID PVC
UNDERDRAIN
BETWEEN PLANTERS
SLOTTED OR
PERFORATED PLASTIC PIPE ~|
(HOLES FACING DOWN)
NOT TO SCALE
DETAIL 1.3 - SILVER AVE. PLANTER BOX PLAN
1|" SCH 40
PVC P PE
.''-/LANDSCAPING STONE ,
2" SCH 40
SUPPLY
w
MANIFOL
SOIL MEDIA
HORIZONTAL REINFORCING NOTES:
1. CONCRETE SHALL BE 560-C-3250 UNLESS OTHERWISE NOTED.
2. REINFORCING STEEL SHALL COMPLY WITH THIS DRAWING UNLESS
OTHERWISE SPECIFIED.
3. REINFORCING STEEL SHALL BE INTERMEDIATE GRADE DEFORMED
BARS CONFORMING TO LATEST ASTM SPECIFICATIONS.
4. BENDS SHALL BE IN ACCORDANCE WITH LATEST ACI CODE.
5. MINIMUM SPLICE LENGTH FOR REINFORCING SHALL BE 30 DIAMETERS.
6. FLOOR SHALL HAVE A WOOD TROWEL FINISH AND, EXCEPT WHERE
USED AS JUNCTION BOXES, SHALL HAVE A MINIMUM SLOPE OF 1:12
TOWARD THE OUTLET.
7. DEPTH V IS MEASURED FROM THE TOP OF THE STRUCTURE TO THE
FLOWLINE OF THE BOX
8. WALL THICKNESS AND REINFORCING STEEL REQUIRED MAY BE
DECREASED IN ACCORDANCE WITH TABLE 1.
9. WALL THICKNESS SHALL BE STEPPED ON THE OUTSIDE OF THE BOX.
10. WHEN THE STRUCTURE DEPTH V EXCEEDS 4'. STEPS SHALL BE CAST
INTO THE WALL AT 15" INTERVALS FROM 15" ABOVE FLOOR TO
WITHIN12" OF TOP OF STRUCTURE. PLACE STEPS IN WALL WITHOUT
PIPE OPENING, OTHERWISE OVER OPENING OF SMALLEST DIAMETER.
ALTERNATE STEP MAY BE AN APPROVED STEEL REINFORCED
POLYPROPYLENE STEP.
12. UPON APPROVAL OF THE ENGINEER, AS DEFINED BY SECTION 6703 OF
THE BUSINESS AND PROFESSIONS CODE, THE USE OF PRECAST
STORM STRUCTURES IS ACCEPTABLE AS AN ALTERNATE TO
CAST-IN-PLACE. PRECAST UNITS SHALL CONFORM TO ASTM
STANDARDS AND BE MANUFACTURED IN A PERMANENT FACILITY
DESIGNED FOR THAT PURPOSED.
11
TABLE 1. BOX SECTION REINFORCEMENT
MAXIMUM SPAN
DEPTH
THICKNESS
HOR.
St FLR.
X OR Y
V
T
REINF.
3'-0" TO 4'-0"
6"
#4
18"
4'-l" TO 7'-0"
4'-0"
6"
#4
12"
7'-l" TO 8'-0"
6"
#4
8"
3'-0" TO 4'-0"
6"
#4
18"
4'-l" TO 5'-0"
4'-l" TO 8'-0"
6"
#4
12"
5'-l" TO 6'-0"
6"
#4 8"
6'-l" TO 8'-0"
6"
#4
6"
I
u
111
H
_
-------
NOT TO SCALE
NOTES:
1. ELEVATIONS ARE RELATIVE, BASED ON BUILDING ELEVATIONS
PROVIDED BY DEKKER/PERICH/SABATINI.
2. DESIGN DOES NOT INCLUDE STORM SEWER INFRASTRUCTURE
REQUIRED TO CONNECT TO EXISTING 60" RCP.
4" OVERFLOW OUTLET
TO EXISTING 60" RCP
STORM SEWER
INTAKE PIPE FROM WEIR
DIVERSION IN EXISTING
60" RCP
LOW-FLOW TRANSFER
PUMP
FLOW: 8 GPM
TDH: 12'
SHALLOW PUMP VAULT
TOP FLUSH TO SIDEWALK
(2) 1500 GAL FIBERGLASS
SETTLING TANK
2" PVC OUTLET
(2) 24" RIBBED PVC RISER
W/ FRP LID
TOP OF SIDEWALK
ELEV, 100,0'
WMmm
2 VN
0 MIM
1" INLET PIPE FROM
PARKING RAMP TANK
SCH 80 PVC
H
ANTI-SIPHON HOLE
INLET PIPE
EFFLUENT
FULL BAFFLE WALL W/
CROSSOVER HOLE
16-0
GATE/BALL VALVE AND
DISCONNECT UNION
TIMER OVERRIDE/ALARM FLOAT
(NO HIGHER THAN TOP OF SETTLING TANK)
INLET/OVERFLOW INVERT
ELEV. 96'-6"
TIMER ENABLE FLOAT
ELEV. 94'-3"
PUMP OFF FLOAT
ELEV 92'-8"
6' DIA PUMP BASIN
8' DEPTH
ACTIVE STORAGE VOL. = 820 GAL
ZOELLER MODEL 141 PUMP
(OR EQUIVALENT)
FLOW: 72 GPM
TDH: 13.2'
DETAIL 2.1 - NUISANCE FLOW PRE-TREATMENT
AND PUMP TANKS
DIVERSION OFF
ELEV. 83'-0"
TANK BOTTOM
ELEV. 81 "-O"
(1) 3/10 HP LOW-FLOW TRANSFER PUMP
FLOW: 2 GPM
TDH: 15-5'
TRANSFER PUMP ON
ELEV. 83'-6" a
FLOAT OFF
ELEV. 82'-6"
TOP OF MANHOLE «-
ELEV. 90'-0'
TOP OF TANK
ELEV. 89'-0"
1" PVC OUTLET PIPE TO
DISTRIBUTION PUMP BASIN
¦ MANHOLE RING WITH GRATE
GRADE AT BOTTOM OF PARKING
RAMP, SLOPED TO GRATE
TABLE 3. FORCE MAIN PIPE SIZES (SCENARIO 2)
NOTES:
1.
REQUIRED STORAGE VOLUME BETWEEN FLOAT OFF
ELEVATION AND OVERFLOW OUTLET IS 3,500 GALLONS.
ACTUAL TANK SIZE WILL BE LARGER TO PROVIDE FOR
OVERFLOW OUTLET. FREEBOARD, AND NECESSARY PUMP
SUBMERGENCE.
TANK DESIGN DOES NOT INCLUDE OVERFLOW OUTLET AND
CULVERT TO EXISTING 60" RCP
TANK DIMENSIONS MAY VARY DEPENDING MANUFACTURER.
TABLE 2. DESIGN PARAMETERS BY SCENARIO
(6) 4-" DIA I 0_IS
stem vi-w
Parameter SCN1
SCN 2
SCN 3
Filter Area (sf)
775
1320
2200
Design Load (gpd)
1550
2640
4400
Distribution Pump
# Doses/day
4
8
12
Vol/Dose (gal)
388
330
367
Dose Time (min)
3.6
5.3
3.9
Parking Ramp Pump
Pump Rate (gpm)
1.1
1.8
3.1
Planter #
Section L
Total L
Nominal D
Inside D
from Pump Basin
ft
ft
in
in
1
2
2
2.5
2.47
2
45
47
2.5
2.47
3
20
67
2.5
2.47
4
39
106
2.5
2.47
5
46
152
2.5
2.47
6
46
198
2.0
2.07
7
42
240
2.0
2.07
8
41
281
2.0
2.07
9
20
301
2.0
2.07
10
46
347
1.5
1.61
11
70
417
1.5
1.61
12
45
462
1.5
1.61
13
45
507
1.0
1.05
14
29
536
0.5
0,60
SYSTEM OPERATION:
DRY-WEATHER PERIODS:
1. STORMWATER IS CONTINUOUSLY PUMPED FROM EXISTING 60" RCP INTO THE SETTLING TANK AT 8 GPM
PUMP RATE CAN BE INCREASED DEPENDING ON ACTUAL DRY WEATHER FLOWS.
2. EFFLUENT FROM THE SETTLING TANK FLOWS TO THE PUMP BASIN, WHERE IT IS DISTRIBUTED TO THE
PLANTER BOXES ON A TIMER-BASED PUMPING SCHEDULE (SEE TABLE 2).
3. MAXIMUM AVAILABLE DOSING VOLUME IN THE PUMP TANK IS 820 GAL, WHICH PROVIDES FLEXIBILITY
FOR DIFFERENT PUMPING SCHEDULES.
WET-WEATHER PERIODS:
4 RUNOFF FROM THE SIDEWALKS IS DIRECTLY TREATED BY THE PLANTER BOXES.
5. RUNOFF FROM THE PARKING RAMP AND ADJACENT SIDEWALK AREAS DRAINS TO THE 3500 GAL
COLLECTION TANK LOCATED UNDER THE PARKING GARAGE.
6. FIRST FLOAT IN COLLECTION TANK TURNS OFF DIVERSION PUMP FROM EXISTING 60" RCP (AND
STOPPING FLOW TO PUMP BASIN) AND OVERRIDES THE TIMER TO DELIVER A FULL DOSE TO THE
PLANTER BOXES.
7. SECOND FLOAT ACTIVATES THE TRANSFER PUMP THAT PUMPS WATER TO THE PUMP BASIN AT A RATE
THAT DOESN'T EXCEED THE DOSING SCHEDULE (SEE TRANSFER RATE, TABLE 2).
8. FLOW VOLUMES IN EXCESS OF THE 3500 GAL CAPTURE VOLUME OVERFLOWTO THE EXISTING 60" RCP.
NOT TO SCALE
TOP VIEW
(G0VH5 k RSF^S REMOVED)
DETAIL 2.2 - 3500 GAL PARKING RAMP
COLLECTION TANK
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Project No.:
Designed By:
Drawn By:
Copyright: Tetra Tech
A-4
-------
Appendix B: Bioretention Soil Media Specifications
B.I General Requirements
Bioretention soil media (BSM) should achieve a long-term, in-place infiltration rate of a minimum of 5 in
per hour.
BSM also should support plant growth while providing pollutant treatment. To achieve those two goals,
the BSM should be a mixture of sand, fines, and compost. The composition shown in Table B-l includes
the measurements for determining the BSM by volume and weight.
Table B-l. Composition of bioretention soil media
BSM
Composition
Sand3
Sandy Loam
Compost
Sand
Silt
Clay
Volume
65%
20%
15%
Weight
75-80%
10% max.
3% max.
9% max.b
Notes', max. = maximum.
a Sand shall be washed with a 75-|jm (No. 200) fraction of no more than 2% (this requirement is stricter than ASTM C-33, but is
extremely important).
b 9% compost by weight results in approximately 5% organic matter by weight.
B.2 Submittals
Product Data: Submit manufacturer's product data and installation instructions. Include required
substrate preparation, list of materials, application rate/testing, and permeability rates.
Verifications: Manufacturer shall submit a letter of verification that the products meet or exceed all
physical property, endurance, performance, and packaging requirements.
Tests should be conducted no more than 120 days prior to the delivery date of the BSM to the project
site. Batch-specific test results and certification will be required for projects installing more than 100
cubic yards of BSM.
The applicant should submit the following materials and information to the municipality for approval if
requested:
• A sample of mixed BSM.
• Results of the grain size analysis of the sand component performed in accordance with
American Society for Testing and Materials (ASTM) D422, Standard Test Method for Particle Size
Analysis of Soils.
• Results of the grain size analysis of the sandy loam soil component performed in accordance
with ASTM D422.
• Results of the grain size analysis of the compost component performed in accordance with
ASTM D422.
• Results of the organic matter content test of the compost performed in accordance with ASTM F
1647, Standard Test Methods for Organic Matter Content of Athletic Field Rootzone Mixes or
Testing Methods for the Examination of Compost and Composting (TMECC) 05.07A, Loss-On-
Ignition Organic Matter Method.
B-l
-------
• A description of the equipment and methods used to mix the sand, sandy loam, and compost to
produce the BSM.
• Results of constant head permeability testing of the mixed BSM. In accordance with ASTM
D2434, Standard Test Method for Permeability of Granular Soils (Constant Head), constant head
permeability testing should be conducted on a minimum of two samples with a 6-in mold and
vacuum saturation.
• The following information about the testing laboratory or laboratories, including:
• Name(s) of laboratory or laboratories
• Contact person(s)
• Address(es)
• Phone contact(s)
• Email address(es)
• Qualifications of laboratory or laboratories, including use of ASTM and U.S. Department of
Agriculture (USDA) method of standards
B.3 Sand Specifications for BSM
B.3.1 Sand Quality
Sand should be thoroughly washed prior to delivery and free of wood, waste, and coatings such as clay,
stone dust, carbonate, or any other deleterious material. All aggregate passing the No. 200 sieve size
should be nonplastic.
B.3.2 Sand Texture
Sand for BSM should be analyzed by a qualified lab using nos. 200, 100, 40, 30, 16, 8, and 4, and 3/8-in
sieves (ASTM D422 or as approved by municipality) and meet the gradation detailed in Table B-2.
Table B-2. Texture of sand
Sieve Size
Percent Passing (by weight)
Min.
Max.
3/8 in
100
100
No. 4
90
100
No. 8
70
100
No. 16
40
95
No. 30
15
70
No. 40
5
55
No. 100
0
15
No. 200
0
2
Notes', max. = maximum; min. = minimum.
All sands complying with ASTM C33, Standard Specification for Concrete
Aggregates, for fine aggregate comply with these gradation requirements.
Sand shall be washed with a 75-^m (No. 200) fraction of no more than 2 percent (this requirement is
stricter than ASTM C-33, but is extremely important).
B-2
-------
B.4 Sandy Loam Soil Specifications for BSM
B.4.1 Sandy Loam Soil Quality
Sandy loam soil for the BSM shall be free of wood, waste, coating (e.g., stone dust, carbonate, and so
forth), and any other deleterious material. All aggregate passing the No. 200 sieve size shall be
nonplastic.
B.4.2 Sandy Loam Soil Texture
Sandy loam soil should comply with the following specifications by weight based on ASTM D422 (or as
approved by municipality):
• 50-74 percent sand
• 0-48 percent silt
• 2-15 percent clay
Note: These ranges were selected from the USDA soil textural classification for a sandy loam, such that
clay content does not exceed 15 percent of sandy loam.
B.5 Compost Soil Specifications for BSM
B.5.1 Compost Texture
A qualified laboratory should analyze compost using No. 200 and 1/2-in sieves (ASTM D422 or as
approved by municipality), and meet the gradation detailed in Table B-3.
Table B-3. Texture of compost
Sieve Size
Percent Passing (by weight)
Min.
Max.
1/2 in
97
100
No. 200
0
5
Notes', max. = maximum; min. = minimum.
B.5.2 Compost Quality Testing
Compost should be a well-decomposed, stable, weed-free organic matter source derived from waste
materials, including yard debris, wood wastes, or other organic materials, and not including manure or
biosolids. Compost shall have a dark brown color and a soil-like odor. Compost that is exhibiting a sour
or putrid smell, contains recognizable grass or leaves, or is hot (120 degrees Fahrenheit) upon delivery
or rewetting is not acceptable.
Compost should be produced at a facility that is regulated by the New Mexico Environment
Department's Solid Waste Bureau. Recent tests of compost quality should be reviewed to verify that the
compost is of acceptable quality.
Compost should comply with the requirements detailed in Table B-4.
B-3
-------
Table B-4. Composition of compost
Parameter
Method
Requirement
Units
Bulk Density
N/A
400-600
dry Ibs/CY
Moisture Content
Gravimetric
30%-60%
dry solids
Organic Matter
ASTM F 1647 or TMECC 05.07A
35%-75%
dry weight
PH
Saturation Paste
6.0-8.0
Carbon:Nitrogen Ratio
N/A
15:1-25:1
Maturity/Stability
Solvita®
> 5
index value
Metals
Arsenic
< 20
Cadmium
< 10
Chromium
< 600
Copper
< 750
Lead
N/A
< 150
mg/kg dry weight
Mercury
< 8
Nickel
< 210
Selenium
< 18
Zinc
< 1400
Pathogens
Salmonella
N/A
< 3
MPN per 4 g
Fecal Coliform
< 1000
MPN per 1 g
Inert Material/Physical Contaminants
Plastic, Metal, and Glass
N/A
< 1%
by weight
Sharps (% > 4mm)
0%
by weight
Notes: CY = cubic yards; lbs = pounds; mg/kg = milligram per kilogram; mm = millimeter; MPN = most probably number
B.5.3 Alternative Organic Amendments
Alternative organic amendments (in lieu of previously defined compost) will be reviewed on a case-by-
case basis. Organic amendments should make up no more than 5 percent of the BSM bulk volume,
unless organic alternatives comply with the specifications of section B.5.2.
B.6 BSM Specifications
BSM shall be free of roots, clods, stones larger than 1 in in the greatest dimension, pockets of coarse
sand, noxious weeds, sticks, lumber, brush, and other litter. It shall not be infested with nematodes or
undesirable disease-causing organisms such as insects and plant pathogens. BSM shall be friable and
have sufficient structure to give good aeration to the soil. The following specifications should govern the
bulk BSM.
B-4
-------
B.6.1 BSM Texture
Gradation Limit: The definition of the soil should be the following USDA classification scheme by weight:
• Sand: 85-90 percent
• Silt: 10 percent maximum
• Clay: 5 percent maximum
Compost should compose no more than 9 percent of the bulk BSM weight and should primarily fall into
the sand component above (per section B.5.1 compost gradation limits).
B.6.2 BSM Quality Testing
In addition to the compost quality testing requirements outlined in section B.5.2, the final BSM should
meet the following standards. Testing results from the specifications detailed in Table B-5 shall be
submitted for approval prior to BSM acceptance.
Table B-5. Composition of media
Parameter
Method
Requirement
Units
Organic Matter
Loss on Ignition
2-5%
dry weight
PH
Saturation Paste
6.0-8.0
-
Carbon:Nitrogen Ratio
-
10:1-20:1
-
Cation Exchange Capacity (CEC)
-
> 5
meq/100 g of dry soil
Salinity (Electrical Conductivity)
Saturation Extract
0.5-3
dS/m
Boron
Saturation Extract
< 2.5
ppm
Chloride
Saturation Extract
< 150
ppm
Sodium Adsorption Rate (SAR)
-
<3
-
Extractable Nutrients
Phosphorus
< 15
Potassium
100-200
Iron
24-35
Manganese
0.6-6.0
Zinc
Ammonium
1.0-8.0
Copper
Bicarbonate/DPTA
0.3-5.0
mg/kg dry weight
Magnesium
extraction method
50-150
Sodium
0-100
Sulfur
25-500
Molybdenum
0.1-2.0
Aluminum
<3.0
Notes'. DPTA = diethylenetriaminepentaacetic acid; dS/m = deci Siemens per meter; meq/100 g = milliequivalents per 100 grams;
ppm = parts per million;
B-5
-------
3,7 Alternative B' . '-_.-ecifications
BSM not meeting the above criteria can be evaluated on a case-by-case basis.
eral lte€|yirerrients
Alternative BSM should meet the following specifications:
• Should be sufficiently permeable to infiltrate runoff at a minimum rate of 5 in per hour during
the life of the facility
• Should provide sufficient retention of moisture and nutrients to support adequate vegetation
while providing pollutant removal
• Should meet the requirements of the compost chemical analysis outlined in section B.5.2 and
the BSM quality testing in section B.6.2
The following guidance is offered to assist municipalities with verifying that alternative soil mixes meet
the specifications.
?krib.r::r::st
The applicant should submit the following material and information to the municipality for approval:
• A sample of the alternative BSM.
• Certification from the soil supplier that the BSM meets the requirements of these guidelines.
• Results of constant head permeability testing of the alternative BSM. In accordance with ASTM
D2434, constant head permeability testing should be conducted on a minimum of two samples
with a 6-in mold and vacuum saturation.
• Results of organic matter content testing of the BSM in accordance with ASTM F1647 or TMECC
05.07A.
• Results of the grain size analysis of alternative BSM performed in accordance with ASTM D422.
• A description of the equipment and methods used to mix the sand and compost to produce the
alternative bioretention soil.
• The following information about the testing laboratory or laboratories:
• Name(s) of laboratory or laboratories
• Contact person(s)
• Address(es)
• Phone contact(s)
• Email address(es)
• Qualifications of laboratory or laboratories, including use of ASTM and USDA method of
standards
• Alternative BSM texture
Alternative BSM should be analyzed by an accredited laboratory using No. 200 and 1/2-inch sieves
(ASTM D422 or as approved by municipality) and should meet the gradation detailed in Table B-6.
B-6
-------
Table B-6. Texture of media
Sieve Size
Percent Passing (by weight)
Min.
Max.
1/2 in
97
100
No. 200
2
5
Notes', max. = maximum; min. = minimum.
B.8 Installation of BSM
This section provides considerations for proper BSM installation.
B.8.1 Considerations Prior to BSM Installation
The following questions and guidelines should be discussed with the contractor prior to installing the
BSM at the project site to prevent any confusion and errors.
• Ensure that the contractor is familiar with constructing bioretention systems.
• Plan how inspections will be handled as part of the construction process.
• Verify that the BSM meets specification prior to delivery and placement in the facility.
• Prevent overcompaction of native soils in areas of the basin where infiltration will occur.
Delineate the facility area, and keep construction traffic off. Protect soils with fencing, plywood,
and so forth.
• Provide erosion control in the contributing drainage areas of the facility. Stabilize upslope areas.
• Ensure that drainage is directed away from bioretention facilities until upslope areas are
stabilized. The concentration of fines could prevent postconstruction infiltration and cause
design failure.
• If drainage is to be allowed through the facility during construction, leave or backfill at least 6 in
above the final grade. Temporarily cover the underdrain with plastic or fabric. Line or mulch the
facility.
• Bioretention facilities should remain outside the limit of disturbance to prevent soil compaction
by heavy equipment. Protect bioretention areas with silt fence or construction fencing.
• Verify that installation of the underdrain is correct prior to placing soil.
B.8.2 BSM Mixing and Placement
Follow these guidelines to ensure proper BSM mixing and placement:
• Implement these erosion and sediment control practices during construction to protect the
long-term functionality of the bioretention:
• Provide erosion control in the contributing drainage areas to the facility and stabilize
upslope areas.
• Do not use facilities as sediment control facilities, unless installation of all bioretention-
related materials are withheld towards the end of construction, allowing the temporary use
of the location as a sediment control facility, and appropriate excavation of sediment is
provided prior to installation of bioretention materials.
• Do not excavate, place soils, or amend soils during wet or saturated conditions.
B-7
-------
• Operate equipment adjacent to the facility. Equipment operation within the facility should be
avoided to prevent soil compaction. If machinery must operate in the facility, use lightweight,
low ground-contact pressure equipment.
• If constructing an infiltrating facility, rip or scarify the subgrade to a minimum depth of 9 in on 3-
ft centers to promote greater infiltration.
• Consider the time of year and site working area when determining whether to mix BSM on-site
or to import premixed soil. It is recommended that the BSM be mixed prior to being delivered to
the site; also, mixing is not allowed on-site during rainy season. If BSM mixing occurs on-site
during the dry season, use an adjacent impervious area or mix BSM on plastic sheeting. (Mixing
should not occur within the bioretention basin.)
• Place soil in 6-12-in lifts with machinery adjacent to the facility (to ensure that equipment is not
driven across soil). If working within the facility, place first lifts at far end from entrance and
place backwards towards entrance to avoid overcompacting.
• Allow BSM lifts to settle naturally, and lightly water to provide settlement and natural
compaction between lifts. After lightly watering, allow soil to dry between lifts. Soil cannot be
worked when saturated, so this method should be used with caution to ensure dry conditions.
After all lifts are placed, wait a few days to check for settlement and add additional media as
needed. No mechanical compaction is allowed.
• The long-term hydraulic conductivity rate should not be less than 5 in per hour when tested with
a double ring infiltrometer (in accordance with ASTM D3385, Standard Test Method for
Infiltration Rate of Soils in Field Using Double Ring Infiltrometer), a single ring infiltrometer, a
Modified Philip-Dunne Infiltrometer, or other approved method.
• Vehicular traffic and construction equipment shall not drive on, move onto, or disturb the BSM
once placed and water-compacted.
• Rake bioretention soil as needed to level out. Verify BSM elevations before applying mulch or
installing plants.
Other Considerations:
• Protect adjacent infiltration systems including swales, soils, and porous pavement from
sediment.
• Protect adjacent trees.
B-8
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