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© 2014 HDR Architecture, Inc., all rights reserved.© 2014 HDR Architecture, Inc., all rights reserved.© 2014 HDR Architecture, Inc., all rights reserved.© 2014 HDR, Inc., all rights reserved.© 2014 HDR, Inc., all rights reserved.© 2014 HDR, Inc., all rights reserved.© 2016 HDR, Inc., all rights reserved.

© 2016 HDR, Inc., all rights reserved.

More Than a Hole in the Ground: Makingthe Most out of Stormwater Management

2017 APWA Stormwater ManagementConference

01 Background and Process

02 Design and Integration

03 The Vision

01 Background andProcess

§ Calgary Factso Same size as NYC but just 10% the populationo 2,300 hours of sunshine a yearo Weird fact – Given a gun and horse when

leave jail

§ Project Playerso Owner & Client – Truman Developmento Planner – CivicWorkso Engineer – HDR & UrbanSystemso Municipality – City of Calgary

West District Project

§ 1st Idea – Total Infiltrationo City concerned with groundwater

contamination§ 2nd Idea – Pond with Open

Spaceo Developer instructed planner to

develop comingled open spacewith pond• All developments are required 10%

of open spaceo Planner found 4th Ward park,

reached out to HDR

Conceptual Stage

historic fourth ward park | atlanta

High-level collaboration between City and Developer prior to design phaseCalgary Development Process

Development Progression

§ Ongoing discussion about park ownershipand maintenance

§ Ensures early investment by developerdoes not go to waste.

§ Formalized submittalso Master Drainage Plan (MDP)o Staged Master Drainage Plan (SMDP)o Pond Report

§ “Final Design” during conceptual stage

Conceptual Design

02 Design and Integration

§ 500 Year Rainfall Event, 24 Hour Durationo 111.3 millimeterso 4.38 inches

§ Chicago Distribution§ Design for 100-year storm, potentially 500-

year storm

Rainfall

§ Dry Ponds, Wet Ponds & Wetlands§ Planned for prior to developmento Preliminarily Sized by City

§ Focus of algae prevention§ Water Quality improvements inherent to

design, provide 85% TSS removal

Stormwater Control

§ Wet Pondo 2.5 L/s/ha allowable unit area release rate (UARR)o Store volume discharging no higher than the UARRo 2-3 meter deep permanent poolo 1 meter minimum active storage deptho 0.3 meter freeboard (~1 foot)

§ Design Stormo 100-year design storm with emergency overflow, 500-

year with no overflowo Continuous modeling, statistical evaluation to

determine 100-year storage from 55-years of datao Most conservative volume of runoff is to be design

volume.

Wet Pond Design Criteria

§ Single Event Analysis – EPASWMMo Green-Ampt Method requestedo Design storms from City of Calgary Stormwater

Manual§ Continuous Modeling – PCSWMMo Green-Ampt Method requestedo 55-years of rainfall datao Daily Temperature Data

§ Statistical Evaluation - HYFRAN

Modeling Approach

Site Specific Hydrologic Results

§ 32.8 hectares – 81.0 acres§ 82 L/s release rate – 2.89 cfs§ 100-year Design Storm – 21,233 Cubic Meters – 17.2 ac-ft§ 100-year Statistical Evaluation – 22,400 Cubic Meters – 18.2 ac-ft§ Continuous Modeling Maximum Volume – 24,670 Cubic Meters – 20.0 ac-ft§ 500-year Design Storm Volume – 27,890 Cubic Meters – Total Volume of Pond Storage 22.6 ac-ft

Wet Pond Design

Uncontrolled Peak Flow Maximum Allowable Outflow148 cfs 2.89 cfs

§ Amphitheatre§ Splash Pad§ Lower Plaza Fountain/Skating Rink§ Restaurant§ Playgrounds§ Orchard§ Community Garden§ Lawn Space§ Preserve Native Aspen Stands

Public Outreach

03 The Vision

Wet Pond and Stormwater Park§ Approach for protecting park functionality

1. Utilized continuous modeling to determinehistorical frequencies of park inundation

2. Designed elevation of features to the 24-hourdesign storm for safety

§ Developer and City created unique goals forthe park functionality.o Perimeter Walkway – 2 Yearo Amphitheatre – 10-yearo Lower Plaza – 50-yearo 500-year does not impact adjacent building

foundations

Park, Meet Pond

west district central park | calgary

§ Utilizing subsurface infiltration toapproximately double pond discharge, inorder to meet level of service requirementsfor the park.

§ Gravelly soils, providing 2.77 m3/day/m2

infiltration rate§ 0.176 cm/s infiltration outflow (6.25 cfs)

Infiltration

§ End-of-pipe treatment - Primary§ Littoral Shelf - Secondary§ Boardwalk Wetlands - Secondary

Water Quality

§ City reviewing design§ Infiltration gallery design§ Water quality analysis§ Maintenance plan§ Final model

Status and Next Steps

Questions?Contact Information:Damian.gaiskiweitz@hdrinc.comPatrick.blandford@hdrinc.com