1133 Melville Street Office Building Development REZONING ... · Bute Street and Thurlow Street...

R A I N W A T E r M A N A G E M E N T R E P O R TMMM GROUP LIMITED

1 1 3 3 M e l v i l l e S t r e e t O f f i c e B u i l d i n g D e v e l o p m e n tR E Z O N I N G A P P L I C A T I O N S U B M I S S I O N

MAY 22, 2015

oxford properties group

kohn pedersen fox associates pc

kasian architecture interior design & planning ltd.

SHARP & DIAMOND LANDSCAPE ARCHITECTURE

CORNELIA OBERLANDER

1 1 3 3 - M e l v i l l e S t r e e t - O f f i c e B u i l d i n g D e v e l o p m e n t - 1 -

1.0 INTRODUC TION

1.2 S i te Locat ion1.3 Stormwater Management Plan Objec t ives1.4 Design Cr i ter ia

2.0 EXISTING CONDITIONS

2.1 General2 .2 R ainfa l l I nformation2.3 Pre -Development Runoff R ate and Volume 3.0 POST-DE VELOPMENT CONDITIONS

3.1 General3 .2 R ainwater Reuse Strategy3.3 Water Qual i t y Control

4.0 CONCLUSIONS

LIST OF APPENDICES

Appendix A Stormwater Management Calculat ionsAppendix B H ydrologic Model OutputAppendix C Oi l Gr i t Separator S iz ing

LIST OF FIGURES

Figure 1 S i te Locat ionFigure 2 Exist ing Condit ions (Or thophoto)Figure 3 Exist ing Condit ionsFigure 4 Proposed Condit ions

LIST OF TABLES

Table 1 R ainfa l l ParametersTable 2 Pre -Development Peak Flow R ate and VolumeTable 3 Proposed Land Use Area BreakdownTable 4 Post-Development Peak Flow R ates and Volume

Table of Contents


1.0 Introduc tion

MMM Group has been reta ined by K as ian Architec ture Ltd. to prepare a repor t in suppor t of the proposed rezoning of 1133 Melvi l le Street in the Cit y of Vancouver. This study presents a R ainwater Management (R WM) plan which meets the accreditat ion requirements for LEED 2009 Stormwater Design SS credits 6 .1 and 6 .2 , and sat is f ies the objec t ives of Vancouver ’s R e z o n i n g Po l i c y f o r S u s t a i n a b l e L a r g e D e v e l o p m e n t s for water quant i t y and water qual i t y control .

1.2 Site Lo cation

The subjec t s i te is located in one of the ‘ ta l l bui ld ings’ s i tes in the Cit y of Vancouver. The area is bound by Bute Street and Thur low Street a long the nor thern and southern s i te l imits , Melv i l le Street to the west , and high-r ise of f ice, commercia l , and res ident ia l development proper t y a long east por t ion. The locat ion of the proposed redevelopment rezoning is i l lustrated in Figure 1 .

1.3 Stormwater Management Plan Objec tives

The objec t ives of the stormwater management plan are as fo l lows:

• Determine s i te speci f ic stormwater management requirements to ensure that the development projec t i s compl iant with the Cit y of Vancouver ’s R e z o n i n g Po l i c y f o r S u s t a i n a b l e L a r g e D e v e l o p m e n t s and LEED NC 2009 stormwater management credits .

• Evaluate var ious stormwater management prac t ices that meet these requirements.

• Recommend a preferred strategy.• Prepare a rezoning repor t documenting the strategy

a long with the technical information necessar y for the s iz ing of the proposed stormwater management prac t ices.

1.4 Design Criteria

The Cit y of Vancouver has issued the R e z o n i n g Po l i c y f o r S u s t a i n a b l e L a r g e D e v e l o p m e n t s in 2010, which provides direc t ion on how to manage ra infa l l ins ide the Cit y ’s jur isdic t ion. A summar y of the ra inwater management cr i ter ia appl icable to this projec t fo l lows:

• Quant i t y : Control the s i te’s post- development runoff rates and volumes generated by the 2-year 24-hour durat ion storm to the pre - development levels .

• Qual i t y : Treat 90% of the average runoff volume to an 85% TSS removal on an average annual bas is .

LEED program design cr i ter ia that address stormwater quant i t y and qual i t y control i ssues include:

• Water Quant i t y Control (S i tes with Exist ing I mper viousness Greater than 50%) – I mplement a stormwater management design that results in a 25% decrease in the rate and volume of runoff based on an analys is of the 2-year 24-hour design storm.

• Water Qual i t y Control – Capture and treat stormwater runoff f rom 90% of the average annual ra infa l l to provide a long-term removal of 80% of the average annual post- development total suspended sol ids ( TSS) .

(Bottom Top) Figure 1. Site Location(Bottom) Figure 2. Site Flow Path

FLOW PATH

STORM MANHOLE


2.0 Exist ing Conditions

2.1 G eneral

The 0 .29 ha s i te is occupied by a 10-storey of f ice bui ld ing bui l t in 1976 with 4 levels of covered car park ing; S ee Figure 2 . Access to the s i te is provided f rom Melvi l le Street . The s i te’s grading s lopes southeast towards Thur low Street . Under exist ing condit ions the s i te is fu l ly imper vious, corresponding to a unit hydrograph method CN value of 98 (equivalent to a runoff coeff ic ient of 0 .90) with drainage ser vice provided by munic ipal storm sewers insta l led in the adjacent streets. P lease refer to Figure 3 for the legal sur vey detai l ing land use detai ls , and exist ing grading and drainage patterns.

2.2 R ainfal l Information

The ra infa l l intensit y for the s i te was calculated us ing the fol lowing equat ion:

I = AT B

Where: I = ra infa l l intensit y in mm/hr T = t ime of concentrat ion in hours A , B = constant parameters (see below)

The parameters (A and B) are taken f rom Meteorological Ser v ice of Canada ( formerly Atmospher ic Environment S er vices) for the Vancouver I nternat ional Airpor t , and are summarized below in Table 1 . An in i t ia l t ime of concentrat ion, TC, of 10 minutes is recommended for catchment 2 .0 ha or less.

Table 1 : R ainfa l l Parameters Return Per iod (years) 2 A 10 .2 B -0 .504

2.3 Pre -Development Runoff R ate and Volume

The LEED pre - development condit ion peak f low rate for the s i te under exist ing condit ions was est imated us ing the 2-year 24-hour design storm for the c i t y of Vancouver and is summarised in Table 2 . To sat is fy LEED SS 6 .1cr i ter ia , which requires a 25% reduc t ion of the exist ing 2-year runoff rate and volume of stormwater runoff f rom the 2-year 24-hour design storm, the target re lease rate f rom the s i te is 11 .3 L/s and the

target volume discharge must not exceed 92.0 m 3 in one 24-hour per iod. Meet ing the LEED Cr i ter ia for th is appl icat ion a lso addresses the Cit y of Vancouver ’s R e z o n i n g Po l i c y f o r S u s t a i n a b l e L a r g e D e v e l o p m e n t s.

Table 2 : Pre -Development Peak Flow R ate & Volume

Land Use Area (m2)

2-Yr 24hr Peak Flow Rate, Q

(L/s)

Target Release Rate (L/s)

(25% Reduction)

2-Yr 24hr Peak Volume

Discharge (m3)

Target Volume Discharge (m3) (25% Reduction)

Existing Site 2,834 15.1 11.3 122.7 92.0

Detailed calculations are provided in Appendix A and hydrologic model output is included in Appendix B.


70.436

40.2

35

70.426

40.2

30

GP

LAN

157

32

STR

ATA

PLA

N B

CS

2321

10 S

TO

RE

Y B

UIL

DIN

G4 B

AS

EM

EN

T L

EV

ELS

STR

ATA

PLA

N V

R 1

286

MA

IN E

NT

RA

NC

E

44°

4

6'

05"

134° 47' 00"

224°

4

6'

55"

314° 46' 45"

PROPERTY BOUNDARY

LEGEND

Figure 3. Existing Conditions

MELVILLE STREET

LANE


3.0 Post-Development Conditions

3.1 G eneral

The rezoning of the s i te proposes the demol i t ion of the exist ing 10-storey bui lding and the construc t ion of a new 33-storey of f ice tower. The new bui lding would provide 6 levels of underground park ing and several low-impac t development features including green roof areas, a l iv ing wal l a long the main pavi l ion, and ra inwater har vest ing for reuse.

The new s i te plan reduces the amount of imper viousness on s i te, down to 94%, which corresponds to a unit hydrograph method CN value of approximately 97. An area breakdown for the s i te layout is provided below in Table 3 . P lease refer to Figure 4 for post- development land use detai ls .

3.2 R ainwater Reuse Strategy

According to LEED cr i ter ia – speci f ica l ly LEED SS Credit 6 .1 – the stormwater management design must result in a 25% decrease in the rate and volume of runoff based on an analys is of the 2-year 24-hour design storm.

The green roof area and the sof t landscaping located at the ground f loor pavi l ion wi l l not generate runoff dur ing smal l ra infa l l events (<5 mm). These systems wi l l be drained by underdrains to the on-s i te c istern. R ainwater f rom the roof wi l l be col lec ted and stored in a ra inwater tank to be c lar i f ied and reused on s i te, reducing the volume of potable water consumed, and meet the long-term goal of a 20% reduc t ion of per capita water consumption.

A 131 m 2 area of green roof i s proposed across the new bui lding on var y ing levels . This water would be returned to the atmosphere through evapotranspirat ion by the green roof vegetat ion. Stormwater runoff f rom the var ious roof sur faces of the bui lding wi l l be col lec ted by roof dra ins and conveyed to a minimum 31.5 m 3 c istern located ins ide the bui lding footpr int . The c istern is f i t ted with a control or i f ice which reduces the discharge leaving the c istern, and achieves the target re lease rate of 11 .3 L/s . A sump volume of 24 m 3 stored ins ide the c istern a l lows col lec ted ra inwater to be c lar i f ied and reused for i r r igat ion of the

onsite plant ings and l iv ing wal l , and/or piped to feed the water feature. Reuse water can a lso be used for cool ing tower make up water ( to replace volume lost to evaporat ive cool ing) and for f lushing of commercia l water c losets.

The ‘H ydroCAD ’ sof t ware pack age has been used to model the behaviour of the proposed SWM system, and determine i ts response under the 2-year 24-hour storm event . This sof t ware ut i l izes a Unit H ydrograph method to est imate peak f low rates and runoff volumes to evaluate the per formance of proposed controls dur ing the design storm event . A summar y of the model led peak of fs i te discharge rates are provided below in Table 4 , and demonstrate that the control led runoff rates re leased f rom the s i te sat is fy the LEED quant i t y control cr i ter ia .

3.3 Water Quality Control

As noted in sec t ion 1 .4 , s tormwater runoff f rom the proposed redevelopment wi l l require water qual i t y t reatment to an 85% TSS removal standard, as per LEED 2009 SS credit 6 .2 . Roof and at- grade runoff wi l l be direc ted to an Oi l /Gr i t Separator (OGS) unit that wi l l t reat the f rac t ion of non- green roof area and atgraderunoff pr ior to discharging i t to the munic ipal out let .

The proposed OGS unit (CDS 2015_4) i s s ized to t reat runoff f rom al l imper vious roof areas and at- grade imper vious sur faces and wi l l provide 85% TSS removal for these t reated areas. Landscaping procedures for the s i te shal l incorporate low-phosphorous fer t i l izers or implement a phosphorous management plan as per LEED 2009 credit 6 .2 . P lease see Appendix C for OGS s iz ing detai ls and per formance repor t .

Land-use Area (m2) % Coverage

Impervious Roof 2,194 77%

Green Roof 131 5%

Soft Landscaping - Planting 53 2%

At-Grade Impervious 456 16%

Total Site Area 2,834 100%

Land Use Area (m2)

Target Release Rate

(L/s)

Post-Development Release Rate

(L/s)

Storage Utilized

(m3)

Target Volume Discharge

(m3)

Post-Development

Discharge Volume (m3)

Post-Development 2,834 11.3 9.7 28.0 92.0 91.3

Table 4: Post-Development Peak Flow Rate and Volume

Table 3: Proposed Land-Use Area Breakdown


Figure 4. Proposed Conditions

Melville Street

Lane South of Pender Street

To Bute Street To Thurlow Street


4.0 Conclusions

A ra inwater management plan has been prepared to suppor t the proposed rezoning of 1133 Melvi l le Street in the Cit y of Vancouver, and in suppor t of the LEED 2009 Stormwater Design credits .

• Water Qual i t y - Al l runoff f rom imper vious sur faces wi l l be suff ic ient ly t reated to meet the standards imposed by the Cit y of Vancouver ’s R e z o n i n g Po l i c y f o r S u s t a i n a b l e L a r g e D e v e l o p m e n t s and LEED 2009 SS credit 6 .2 .

• A 25% reduc t ion of the 2-year 24-hour peak f low rate as per the LEED 2009 Stormwater Design SS credit 6 .1 was achieved through the use of a stormwater tank , sof t landscaping, and green roof area which a l low for water to be natural ly reta ined on s i te through evapotranspirat ion or inf i l t rat ion.


Appendix A - Stormwater Management Calculations


Summary for Subcatchment 1EX: Existing Building Drainage Diagram for 1133 Melville LEED

Subcatchment 1EX: Existing Building

Appendix B - Hydrologic Model Output

Legend


Area Listing (Selected Nodes) Summary for Subcatchment 1R: Green Roof

Subcatchment 1R: Green Roof


Summary for Subcatchment 3R: Impervious Roof Summary for Subcatchment 5G: At-Grade

Subcatchment 3R: Impervious Roof Subcatchment 5G: At-Grade


Summary for Pond 2R: Green Roof

Pond 2R: Green Roof


Summary for Link 6: (New Link)Summary for Pond 4: Re-use Tank

Pond 4: Re-use Tank

Link 6: (New Link)


Area: 0.29 ha 191Runoff C: 0.9

Tc: 10 minutes OK110 micronsCDS Model: 2015-4 19.8 l/s

1500 l/s l/s

Rainfall Intensity1

(mm/hr)

Percent Rainfall Volume1

Cumulative Rainfall Volume

% Rainfall Volume Treated

Total Flowrate

(l/s)

Removal Efficiency2

(%)

Incremental Removal

(%)0.5 13.6% 13.6% 13.6% 0.4 89.9 12.21.0 15.9% 29.5% 15.9% 0.7 89.4 14.21.5 16.0% 45.5% 16.0% 1.1 89.0 14.22.0 13.3% 58.8% 13.3% 1.5 88.5 11.82.5 10.9% 69.6% 10.9% 1.8 88.1 9.63.0 8.5% 78.1% 8.5% 2.2 87.6 7.43.6 5.1% 83.3% 5.1% 2.6 87.1 4.54.1 4.6% 87.8% 4.6% 2.9 86.7 4.04.6 3.4% 91.2% 3.4% 3.3 86.2 2.95.1 2.3% 93.5% 2.3% 3.7 85.8 2.06.4 3.0% 96.6% 3.0% 4.6 84.6 2.67.6 1.3% 97.9% 1.3% 5.5 83.5 1.18.9 0.8% 98.7% 0.8% 6.5 82.3 0.7

10.2 0.3% 99.0% 0.3% 7.4 81.2 0.311.4 0.2% 99.2% 0.2% 8.3 80.0 0.212.7 0.6% 99.8% 0.6% 9.2 78.9 0.419.1 0.0% 99.8% 0.0% 13.8 73.2 0.025.4 0.1% 99.9% 0.1% 18.4 67.4 0.138.1 0.0% 99.9% 0.0% 27.6 47.1 0.050.8 0.1% 100.0% 0.0% 36.9 35.3 0.0

88.199.9%88.1%

1 - Based on 46 years of hourly rainfall data from Canadian Station 1108447, Vancouver BC2- Removal Efficiency based on constant sediment influent concentration at all flow rates

Predicted % Annual Rainfall Treated =

BASED ON THE RATIONAL RAINFALL METHOD

CDS Hydraulic Capacity:

Rainfall Station* # (*closest rainfall station to site)

Predicted Net Annual Load Removal Efficiency =

BASED ON A PARTICLE SIZE OF 50 MICRONS AND LARGER

CDS ESTIMATED NET ANNUAL SOLIDS LOAD REDUCTION

1133 MELVILLE STREET - VANCOUVER, BC

Appendix C - Oi l Grit S eparator Sizing (from R ainwater Management)

S I Z I N G E S T I M AT E PAC K AG E

Engineering Information

• Control led Flow : None • Removal Target : 85 % removal of the 50 micron and

larger par t ic les (NJDEP PSD) .

Engineering Information

• The CDS Technologies Stormwater unit for this projec t has been designed to remove 85 % TSS annual ly. This i s based on the Par t ic le S ize Distr ibut ion def inedby the NJDEP. P lease see graph below.

Drainage Area

Runoff Coefficient

CDS Model Net Annual

Removal

0.29 ha 0.9 CDS2015-4 88.1 %

0102030405060708090

100

10 100 1000

% F

iner

Particle Size (micron)

• The sediment inf luent concentrat ion is assumed to be constant over the ful l range of f lows result ing in more accurate predic ted removal ef f ic iencies.

• The peak f lows wi l l be conveyed through the unit without re -suspending the previously t rapped pol lutants. The sediment storage sump is separate f rom the high f low area.

CDS Technologies Summar y

The CDS Technologies Stormwater Treatment System is a t rue hydrodynamic (swir l concentrator) o i l /gr i t separator that combines screening and enhanced gravit y sett l ing to remove f loat ing, neutra l ly buoyant and non-buoyant sol ids f rom stormwater runoff. The non-block ing screen captures 100 % of the pol lutants equal to the screen aper ture s ize (2400 microns and larger) and is propr ietar y to CDS Technologies. A l l non-buoyant sol ids are direc ted to a sump that separates the captured pol lutants f rom the treatment f low path to prevent the larger storm events f rom re -suspending previously t rapped mater ia l . The f loatable debr is and oi l /grease are t rapped upstream of the baff le for easy removal .

The CDS Technologies Stormwater Treatment System can be insta l led as a bend struc ture, can accommodate mult iple in lets , and does not require an e levat ion di f ference bet ween the in let and out let p ipes.

The CDS has been tested in accordance with a number of industr y-accepted test protocols inc luding the NJDEP laborator y protocol , the I ndianapol is laborator y standard, the Washington Depar tment of Ecology laborator y standard and the TARP Tier I I f ie ld test ing protocol . A number of addit ional laborator y tests have been executed on the CDS us ing industr y-accepted test ing prac t ices and sample analys is procedures. Al l of the test ing conduc ted on the CDS in order to document per formance and ref ine s iz ing methodologies has been executed on ful l -scale CDS units . The vast major i t y of CDS test ing has been executed by or fu l ly overseen by independent 3rd par t ies. I t i s s tandard prac t ice to s ize the CDS to meet local cr i ter ia us ing the results of fu l l

scale laborator y test ing across a fu l l range of expec ted treatment rates.

Maintenance is a key to any oi l /gr i t separator system for proper long-term ef fec t iveness. CDS a l lows for unobstruc ted access without conf ined space requirements. R ainwater Management is avai lable to t ra in a maintenance crew or to provide regular inspec t ion/maintenance ser v ices.

Fol lowing is a s iz ing table and general drawing.



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