2005 Auburn Research Park Master Plan

To that end, several placemaking goals, noted in the business plan, and in conver-stations with the Task Force guided the development of the plan: · To reinforce the intellectual connect

AUBURN RESEARCH PARK MASTER PLAN

table of contents

the planning context 3

1.1 MISSION 4

1.2 VISION 4

1.3 VALUE PROPOSITION 5

1.4 PARK FEATURES AND REAL ESTATE DYNAMICS 5

1.5 CLUSTERS OF INTEREST 6

1.6 GOALS AND OBJECTIVES 7

the physical planning background 9

2.1 THE SITE CONTEXT 9

2.2 THE DEVELOPMENT PROGRAM 10

the master plan .13

3.1 DEVELOPMENT STRATEGY 13

3.2 LAND USE ORGANIZATION 13

3.3 LANDSCAPE STRUCTURE 16

3.4 MASTER PLAN CAPACITY 19

hydrology 21

4.1 STORMWATER ANALYSIS 21

4.2 EXISTING HYDROLOGICAL CONDITIONS 22

4.3 STORMWATER STRATEGY 22

integrated transportation 29

5.1 PEDESTRIAN CIRCULATION 30

5.2 BICYCLE CIRCULATION 32

5.3 TRANSIT 32

5.4 VEHICULAR CIRCULATION 33

5.5 PARKING 35

design brief .37

6.1 SITE DESIGN GUIDANCE 37

6.3 LANDSCAPE GUIDANCE 42

6.3 ARCHITECTURAL GUIDANCE 48

sustainable design features 51

The Auburn Research Park (ARP or the Research Park) is envisioned as a vibrant,

new district on the Auburn campus It will be a center for interaction and

collabo-ration focusing on the research and academic strengths of the University It will

become the locus for Auburn’s private/public partners and affiliates who have a

direct interest in the research activities of the University It will be a hub for the

social networks that emerge as a result of collaboration on research activities and

will serve as a major center in the East Alabama region for the formal exchange

of technical information It will support an entrepreneurial culture based on the

research and academic strengths of the University

The Research Park will be a source of knowledge generation in the region It will

play a role in educating the regional work force and providing the scientists,

engi-neers and technicians necessary to support regional economic objectives It will

provide support to businesses and industries that may emerge as a result of the

research activities in the park

The Auburn Research Park master plan sets out a physical design framework for

guiding the incremental implementation toward this vision The master plan is

supplemented by and coordinated with the master plan for Auburn University

campus It should be reviewed in the context of the master plan, which

estab-lishes campus-wide goals and objectives

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Illustrative Plan

the planning context 1

The planning process for the Research Park has evolved under the direction of the

Auburn Research Park Task Force and has included several stages Initial studies

focused on the selection of the current site and a strategic market analysis The

site selection process was carried out in 2003 and involved an assessment of

sev-eral properties in the Auburn area owned by the University The proposed South

Campus location was selected for its proximity to the main core of the campus,

visibility and accessibility to the regional road network The process included the

development of an accommodation strategy for the potential facility sizes

identi-fied in the market analysis completed by Hammer Siler George

Subsequent studies include a business plan, which articulates the mission, vision

and values for the Research Park, and offers guidance on the desired character

for the physical environment The business plan sets out a strategy and timeline

for the development of the Research Park over the next twenty years

In developing the physical plan for the Research Park, the business plan was

reviewed with “place” in mind Specifically, it was reviewed to determine how

the mission, vision and values could influence the type of place that the Research

Park becomes and to determine how this sense of place could support the

mis-sion, vision and values This section summarizes some of the key points of the

business plan that influenced the development of the physical master plan

envi-· stimulates the development of a knowledge-based economy;

· enhances University technology transfer and sponsored research,

· fosters economic growth; and,

· supports the mission of Auburn in research, instruction and outreach through collaboration and entrepreneurial relationships between the University and the business community

This mission implies that the Research Park should become a center for interaction among the many players in the regional economy that have a particular interest in the research activities of the University As a center, it will need to facilitate inter-action among University and public / private partners This suggests a mixed-use environment where University and public/private uses share research, office and support facilities It further suggests an environment that facilitates formal and informal interaction among the tenants of the Research Park

1.2 VISION

The business plan states that the Research Park should become a destination—an environment that is stimulating and interesting not only to the research partici-pants, but also to the local community, to the University community and to the State

The vision is fourfold:

1 Support the mission of Auburn University and confi rm Auburn as the leading research force of the East Alabama region;

2 Create new revenue sources for the University;

3 Broaden and strengthen the research industry in East Alabama; and,

4 Produce an economic development engine for Alabama and the region

The vision further demonstrates the need for an environment that will foster laboration among the tenants of the Research Park and an environment that serves

col-as an “information” locus for business and industry in the region

1.3 VALUE PROPOSITION

The business plan sets out the value proposition for the Research Park stating that

it will sponsor cutting edge interdisciplinary research combined with academic

consolidation

• ARP will provide, over the long-term, “centers of excellence” for engineering

and biological sciences (including agriculture, veterinary medicine and

biotechnology)

• ARP will distinguish itself by combining cutting edge research, creative

problem solving, academic and research collaboration, technology transfer

resources, and economic development initiatives, in a comfortable

and collaborative research village retreat environment near the main

concentration of the University

Building on the small-town University community image of Auburn, the value

proposition begins to suggest a village-like environment that reflects the

commu-nity values of the University and Auburn itself

1.4 PARK FEATURES AND REAL ESTATE DYNAMICS

The business plan articulates several specific placemaking features envisioned for

the Research Park:

• ARP will create a sense of community that fosters transfer of information and

collaborative uses of resources

• ARP will include destination centers that will invite the community to

experience the Park

• Covenants will allow building designs to fi t into an agreed architectural format

while encouraging individuality

• Facilities will encourage gathering of faculty, business leaders and graduate

students

• ARP will be tied to the fabric of the University and the Auburn Community

The real estate dynamic and placemaking recommendations are stated as follows:

• ARP will be a unique, mixed-use, research and academic community that

provides a full range of facilities and support to its occupants and visitors

• A highly interactive assemblage of University, corporate and government

facilities….involved in research and development, teaching and learning, or

public service in a multidisciplinary theme

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• The parking will incorporate natural topographic features such as wetlands, streams, woods, etc and maintain open areas and green space in keeping with the University’s origins as a land grant institution

• ARP will evolve using Clusters of Interest to organize the Park and provide a sense of community

• The cluster concept will allow similar disciplines to congregate but also to be part of a larger community

Similar to the mission and vision statements, the real estate dynamics articulated

in the plan suggest a compact, pedestrian oriented environment integrated with the features of the land

1.5 CLUSTERS OF INTEREST

The research strengths of Auburn University are in engineering and biological ences (including agriculture, veterinary medicine and biotechnology) The busi-ness plan suggests a long-term goal of organizing the park in clusters Each cluster would include University, private sector and public sector agencies focusing on the specific “interest” or an aspect of that interest

sci-The long-term goal of providing Clusters of Interest is summarized in the business plan as follows:

• Clustering buildings with a human scale dimension

• Focus around common, landscaped open spaces with varying character

• A mixed-use development, including housing, industry and government

research activities

• Visible outdoor activities

• A physical and visual connection with other adjacent neighborhoods

• Food services and other gathering spaces

1.6 GOALS AND OBJECTIVES

In developing the master plan for the Research Park, the importance of place in

supporting the vision and research goals is given high priority The creation of a

destination and center for the social network of individuals and organizations with

an interest in the research and academic activities of the University is seen to be

critical to the long-term success As a place, it will need to integrate and

facili-tate the intellectual and research connections between the Research Park and the

Auburn campuses

ARP intends to create a campus environment that facilitates collaboration,

inno-vation and cooperation between the significant intellectual and academic

resourc-es of the University and potential partners whether they be institutresourc-es,

govern-ment entities or the private sector

To that end, several placemaking goals, noted in the business plan, and in

conver-stations with the Task Force guided the development of the plan:

· To reinforce the intellectual connections between the Research Park, the main

campus and other academic / research centers of the University

· To create an attractive, strong physical identity for the Research Park

· To create an environment that fosters a culture of creativity, innovation and

entrepreneurship for established businesses as well as start-ups (incubators)

· To create a plan that demonstrates sensitivity to the natural environment,

existing surrounding land use patterns and opportunities in the surrounding

area

· To plan for fl exibility, growth and private investment over the long termTo

create a vibrant environment for collaboration

· To focus on sustainable planning and design by providing

–A Pedestrian oriented environment

–An Integrated approach to transportation

–A park-wide stormwater and water quality management strategy

–Buildings designed to LEED Guidelines

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Context Map

The master plan is informed by a review and analysis of the surrounding site text and the twenty year development program set out in the business plan This section summarizes the major site and program considerations.

con-2.1 THE SITE CONTEXT

The site selected for the Research Park offers many features that reflect the gin of the University as a land grant institution It includes a riparian and wetland zone to the south and the Campus Forest to the north

ori-The site is located approximately two (2) miles south of the main University Campus The 156-acre area approved for development is part of a larger context that will provide a unique landscape setting for the park The proposed develop-ment area is located along the top and partially down the southern slope that runs along Camp Auburn Road The topography of the site rises from elevation

610 along South College Street to elevation 675 at the highest point The ridge forms a minor watershed boundary dividing the stormwater runoff of the site into a north and south slope Runoff from the northern slope discharges overland directly to Parkerson Mill Creek, a major stream that flows from the main campus further to the north

Existing land uses include the Poultry Unit, which is due to be relocated to make way for the proposed Research Facilities Adjacent land uses include low-density suburban development to the east, primarily garden apartment units, and strip commercial centers

Existing circulation is limited to an east/west route through the site known as Camp Auburn Road

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Early Development Program

2.2 THE DEVELOPMENT PROGRAM

The development program for the Research Park includes 990,000 gsf of space

to be developed over a twenty-year period The development program is based

on that provided in business plan and is summarized in the following table In addition to GSF of building area, the estimated land for required for develop-ment and parking is provided It should be noted that the development program assumes that each building will be developed on a single site including all of the requisite parking

BUILDING GSF ACREAGE

LEASED

PARKING AREA

Note: The Early Development Program is based on the

Business Proforma completed in the Spring of 2005

The Research Park site is

surrounded by a landscape

that is rural in character

Ponds & Wetlands dominate

the landscape south of the

Research Park site

The Campus Forest is

located north of the

Research Park Site

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Illustrative Plan

The master plan for the Research Park accommodates the proposed long-range

development program and provides a vision for implementation that addresses the

vision, mission and values set out in the business plan This section describes the

key elements of the master plan

3.1 DEVELOPMENT STRATEGY

The Research Park master plan will guide the development of a new campus

dis-trict that facilitates collaborative research and interaction among researchers,

faculty, staff and students and private/public sector partners

The master plan supports the mission, vision and values set out in the business

plan with an overarching goal to provide an environment based on sustainable

design principles and to create a unique place in tune with the climate, landscape

and history of the Auburn University campus

The master plan sets out a vision for a compact, pedestrian oriented environment

with a unique sense of place The sense of place emerges from the natural beauty

of the site—its hilltop location with a foreground of ponds and backdrop of forest

The intent is to create a hill-top “village-like” environment providing views across

the ponds that defines the south campus area

3.2 LAND USE ORGANIZATION

The master plan organizes the Research Park into several distinct areas linked by

the landscape framework, and the pedestrian and vehicular circulation systems

The vehicular circulation structure consists of two main roads: a

reconfigura-tion of the Camp Auburn Road alignment, extended to connect to Shug Jordan

Parkway; and a loop road, which will link S College Avenue to Donahue

5

The pedestrian circulation system consists of a primary east/west pedestrian spine

or Hilltop Spine through the Research Park which connects three clusters of

devel-opment North /south pedestrian routes link the Hilltop Spine with buildings

pro-posed north of Camp Auburn Road and with the existing and propro-posed nature trails

within the Campus Forest

The long-term goal of providing clusters of interest is intended to result in distinct

groupings of facilities that can be organized by research focus or other functional

/ organizational concepts that may emerge as the Research Park develops This

directly responds to the Clusters of Interest noted in the business plan Spatially,

the clusters have been designed to define distinct zones within the research park

structure, in particular along the hilltop

Conceptually, the major research spaces of the Research Park are arranged along

the central hilltop of the site This hill-top “village” is organized by the east / west pedestrian spine, auto arrival courtyards, and north/south landscape corridors It

includes the following clusters:

East cluster- the East Cluster will be the site of the first phase of development and

includes two buildings totaling 130,000 GSF Given the prominence of the cluster

along the main entry road, it will form a major landmark The cluster potentially

will feature a tower element and public terrace in the southeast corner at the

terminus of the hilltop pedestrian spine The approved development in the East

Cluster will establish the architectural character for the entire Research Park

The East Cluster will be defined on the east and south by proposed buildings and

on the west by one of the proposed landscape corridors, which function as a link

between the Campus Forest to the north and the riparian areas to the south The

corridor also serves as a detention area as part of the stormwater management

strategy

In addition to grouping users with a specific interest, each cluster of buildings is

intended to provide spatial definition to the parking lots The parking lots provide a base line of core parking needs for the surrounding buildings in a garden-like envi-

ronment

Central Cluster – the central cluster is the largest of the three clusters and is

located on the site of the existing Poultry Unit It is defined by buildings on the

south, east and west which serve to define the parking court

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The central cluster includes a site for a future public building which could house convenience retail, food service, conferencing or other activities of importance to the users across the Research Park The central location of this facility will pro-vide users of the park with the type of collaboration and meeting space essential

to the interdisciplinary research mission articulated in the business plan

West Cluster - The west cluster includes three facilities which define a courtyard

around which public amenities and uses could be organized It will serve as the gateway feature for visitors entering from Shug Jordan Parkway to the west

North Zone – The major parking areas for the Research Park are located north of

Camp Auburn Road This area also includes sites for future buildings such as a new Faculty Club or public / common facility and other research / office buildings The site identified for the Faculty Club has been positioned at the end of a north/south landscape corridor, where it is envisioned as a landmark feature As with the public facility proposed in the central cluster, it will be one of the social and col-laboration facilities proposed for the Research Park

potential uses and research partners, the master plan includes an area for tor and small-scale uses that may require stand-alone facilities Permitted uses in this area are those which complement the research strengths of the University or serve major government or private sector partners that require space that cannot

incuba-be feasibly located in multi-use research / office buildings such as those proposed along the hilltop pedestrian spine

3.3 LANDSCAPE STRUCTURE

The landscape framework for the Research Park responds to the unique aspects of the south campus, in particular, the riparian environment of the ponds and associ-ated wetlands, and the Campus Forest in the higher areas of the site The frame-work demonstrates sensitivity to the context by preserving these areas as visual and passive recreational amenities for the Research Park tenants, the Auburn Campus as well as the broader community

The south campus environment of ponds, wetlands and wooded areas distinguishes Auburn University from the surrounding suburban commercial development It serves as a reminder of the land grant heritage of Auburn and is important to the sustainable principles including habitat protection, water quality, stormwater management and air quality

Conceptually, the riparian areas provide a foreground landscape to the hilltop development The entire foreground is considered to be a gateway to Auburn

0 200 400 600

north

Landscape Structure

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University and the Research Park When viewed in conjunction with the hilltop lage” arrangement of buildings, the intent is to provide a unique and memorable impression of the University

“vil-The riparian and forest landscapes are deliberately kept in their natural states with

an overlay of man-made elements such as the regulating lines established by the existing dams and a system of walking and jogging trails Intervention in the exist-ing landscape is minimized to ensure that the existing natural character can be maintained in perpetuity and to focus investment in the landscape in those areas that park users will utilize daily including the pedestrian routes and arrival courts.The Campus Forest north of Camp Auburn Road is largely maintained in the master plan The intent is to provide a green backdrop for the Research Park The Forest

is considered to be of value as a natural resource, for the educational and passive recreational opportunities it provides, and for its value in terms of habitat, water quality, carbon absorption and microclimatic benefits Preservation of the Campus Forest is a key objective of the campus master plan

The landscape structure includes several areas distinguished by design and scape concepts:

Street Right of Ways: the proposed street right-of-ways are designed to provide a memorable and unified corridors through the Research Park The ROW along Camp

Auburn Road is defined by a double row of street trees on the north and south

side of the roadway A sidewalk and utility corridor is provided along the south

side of the street and a bicycle path is provided on the north

Hilltop Pedestrian Spine – the pedestrian spine will feature planting for shade

and protection in addition to that provided by the adjacent buildings The spine

is envisioned as the major activity corridor on the site It will provide a link

between the clusters and to the proposed central common facility

Arrival Courts – the arrival courts will feature shade trees to create a pleasant

arrival point and convenient front-door access to surrounding buildings

Parking Areas – the parking lots include vegetated swales planted with water

tol-erant trees and plants, the intent of which is to provide an area for stormwater

recharge, provide shade in the parking areas and reduce the “heat sink” effect

of such large paved areas

3.4 MASTER PLAN CAPACITY

The master plan illustrates how 1 million square feet of development can be

accommodated over time The objective is to accommodate this development in

a compact land use pattern organized along a pedestrian spine and major

pedes-trian routes

PARCEL SIZE (ACRES) APPROXIMATE

BUILDING AREA (GSF)

Food Services

Development Capacity Table

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Illustrative Plan

A goal of the master plan is to minimize the amount of stormwater channeled

off-site and instead rely on on-off-site recharge

Low Impact Development (LID) stormwater management techniques are

recom-mended in lieu of traditional development methods which channel runoff through

manmade structures into a municipal system LID is defined as methods of

devel-opment dedicated to protecting the environment and water resources through site

design techniques that replicate pre-existing hydrologic site conditions

A development that includes LID design practices resulting in less impact to area

streams, wetlands, and wildlife habitat by maintaining undisturbed rainwater

flow paths and providing a high standard of water quality Maintaining natural

areas results in higher levels of infiltration which recharges groundwater supplies,

streams, and wetlands

Research indicates that LID, if designed and constructed properly, can greatly

improve the quality of stormwater runoff; reduce development impacts such as

erosion and flooding; reduce project costs; and improve the natural aesthetic of

the development LID uses the natural features of the site and a variety of best

management practices (BMP’s) to deal with stormwater

4.1 STORMWATER ANALYSIS

The master plan includes a stormwater management concept plan for the entire

Research Park site It also provides recommendations for the surrounding forest

and riparian areas of the South Campus

The following assumptions apply to this analysis:

· Soil information is based on mapping by the National Resources Conservation

Service (NRCS)

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· Preliminary runoff calculations are based upon the NRCS Technical Releases 20 and 55 The existing surface conditions are assumed to be a combination of grassland and woodlands

· Detention volumes are based on the City of Auburn Stormwater Management Manual, which indicates a requirement for post development runoff rates for

a 25-year storm to match or be reduced from existing conditions The storm distribution is aType III 24-hour storm

· Stormwater detention within the existing water bodies is not explored, as this potential should be discussed with the regulating authorities

4.2 EXISTING HYDROLOGICAL CONDITIONS

The topography of the Research Park site rises from elevation 610 along South College Street to elevation 675 at the highest point The ridge along Camp Auburn Road acts as a minor watershed boundary dividing the stormwater runoff of the site into a north and south slope Runoff from the northern slope discharges over-land directly to Parkerson Mill Creek The southern slope runoff discharges over-land to a system of the tributaries, which ultimately discharge to the Parkerson Mill Creek According to the National Resource Conservation Service (NRCS), the Research Park site consists of well drained soils of Hydrologic Group ‘B’ The ground cover is composed of dense woodlands in good condition along the north-ern slope and grassland on the southern slope

4.3 STORMWATER STRATEGY

The primary concerns of the stormwater analysis for the Research Park are water quality control, groundwater infiltration and peak rate runoff for compliance with the City of Auburn Stormwater Management Manual and Alabama Stormwater Regulations per the National Pollution Discharge Elimination System (NPDES) This analysis suggests that the above can be accomplished through the incorporation of several BMP’s

Stormwater impacts associated with the proposed master plan configuration can

be minimized and, in many cases represent improvement over existing conditions

by the integrating numerous BMP’s Stormwater runoff within the Research Park should be directed through most, if not all, of the below noted practices with the exception of the roadways

0 200 400 600

north

Stormwater Concept Plan

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It should be noted that the roadways are designed using a traditional closed drainage system Given this condition, a decentralized discharge of roadway runoff into a system of shallow detention/infiltration basins with flow diffusing discharge methods is recommended Use of all recommended BMPs, as well as the potential use of existing site features for the purpose of stormwater management, should be discussed with the appropriate state and city regulators prior to pro-ceeding with design

The stormwater concept plan illustrates a schematic layout of potential surface storage areas, pervious pavement locations and a system of conveyance and dis-charge practices Assuming that each suggested detention area is 3 to 4-feet deep and that pervious pavement is provided at all parking stalls and pervious pavers are used within pedestrian areas, the plan represents the scale of required storm-water detention

Parking Area Stormwater Concept

The proposed impervious parking, building and roadway areas account for

approximately 20 percent of the total 156 acre site or approximately 34 acres

Based on the soils, surface conditions and the City of Auburn Stormwater

Management Manual which requires onsite detention for the 25-year storm

(7.2-inches), the masterplan design requires an estimated 520,000 cubic feet of

detention volume within the site

To achieve these detention targets, the master plan includes all of the following

BMP’s

Vegetated Filter Strips - vegetated surfaces, usually grass or natural ground

cover that treat sheet flow from adjacent surfaces and remove pollutants

through filtration and infiltration The numerous proposed and existing

undis-turbed vegetated buffers throughout the site act as filter strips It is

recom-mended that filter strips be located adjacent to most paved surfaces and at

the overflow aprons of each level spreader (pipe discharge areas) Filter strips

should be composed of grass or natural groundcover

Bio-retention - a soil and plant based stormwater management technique

employed to filter runoff from impervious areas Bioretention consists of a

porous soil covered with a thin layer of mulch Typically soil media consists of

50-60 percent sand with an infiltration rates greater than 1.5 inches per hour

A stand of various water tolerant grasses / shrubs and small trees is planted to

promote evapotranspiration, maintain soil porosity, encourage biological activity

and promote uptake of pollutants

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The process consists of an inflow of untreated stormwater runoff, which is

retained within the vegetated area up to six (6) inches in depth This accumulated runoff is then infiltrated through the permeable soil media which acts to filter out the contaminants and pass the treated stormwater either into the groundwater table or to a sub drainage system Contaminants captured in the soil media are then absorbed by the plant root systems and processed naturally Runoff which accumulates to a depth greater than six (6) inches will discharge to overflow inlets within the bioretention area These systems are located in the medians between parking rows and at the edges of parking areas

Vegetated Water quality swales - dry vegetated channels explicitly designed and constructed to capture and treat stormwater Vegetated swales are typically shal-low 0.5 to 1-foot deep and sloped no more than two (2) percent to provide low velocity flows and facilitate infiltration and contaminant removal These replace the need for standard closed drainage systems and are located adjacent to drive-ways, parking areas, pedestrian areas and are used for the conveyance of concen-trated flows

Porous Pavement - a permeable pavement surface with an underlying stone voir designed to temporarily store surface runoff before it infiltrates into the sub-soil Porous pavement materials can be either cement concrete or bituminous con-crete and may take the form of poured in place materials or paving units Porosity

reser-is based on larger aggregate sizes, less fine materials and add-mixtures necessary

to maintain structural integrity

Porous pavement is proposed in the master plan along the pedestrian routes and in parking stalls to reduce the amount of runoff from paved areas and allow captured rainfall to infiltrate back into the groundwater

Reinforced turf - an integration of turf or lawn cover with a structural member such as a geotextile mesh, polyethylene mat, concrete pavers, etc This integra-tion allows for the storm water filtration and infiltration benefits of a lawn cover

as well as the structural integrity to accommodate vehicular loading and/or a reduction in erosion caused by high velocity stormwater runoff These should be located in all vegetated areas with potential for erosion such as the down gradient

of pond outlet flow diffusers, and vegetated swales with slopes greater than five (5) percent

Perforated high density polyethylene drain pipes - allow for infiltration to the

groundwater table and, thus, reduce discharge flows from the collection system In

addition, HDPE pipes are preferable to PVC in that fewer toxic additives are used

during the manufacturing process resulting in reduced leaching potential in landfills

and reduced potential for dioxin formation during burning They are also more

read-ily recycled

Perforated HDPE pipes are proposed in the stormwater concept plan wherever closed

drainage is necessary and installed at minimum slopes to allow for infiltration

Deep sump hooded catch basins - storm drain inlets that typically include a grate or

curb inlet and a sump to capture trash, debris and a hooded outlet to capture oil and

grease Stormwater enters through and the inlet grate at the top of the structure

and exits through an outlet pipe equipped with a hood for the purpose of trapping

the oils and floatable materials within the basin Heavier debris will then settle out

into the sump provided below the outlet pipe These are proposed wherever curb,

gutter and standard catch basins are necessary

Surface/Sub-Surface Detention/Infiltration Systems - excavated trenches or basins

used to detain stormwater and allow infiltration into the surrounding soils from the

bottom and sides of a basin or trench The basins or trenches are either left open

and landscaped or supported with arch shaped HDPE structures and backfilled

The master plan stormwater concept calls for a decentralized system of detention

areas with the intention storing and infiltrating stormwater where it falls Arched

HDPE structures are proposed beneath the bioretention swales proposed for the

parking areas to capture and infiltrate the average annual rainfall runoff The

emer-gency overflow from the larger more infrequent rainfall events is directed to shallow

surface basins for temporary detention and infiltration prior to being discharged by

through flow diffusers

Flow Diffusers - structures located at the discharge point of a stormwater pipe and

designed to uniformly diffuse concentrated flows into shallow low velocity sheet flow

for the purpose of reducing the erosive effects and allow for more effective water

filtration Flow diffusers are proposed at all discharge points from closed drainage

systems and detention areas