M E M O R A N D U M DATE: FEBRUARY 27, 2015 LILY XU (CITY OF OTTAWA) JOCELYN CHANDLER (RVCA) CONRAD STANG / MICHAEL PETEPIECE

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1 DATE: FEBRUARY 27, 25 M E M O R A N D U M TO: FROM: RE: CC: LILY XU (CITY OF OTTAWA) JOCELYN CHANDLER (RVCA) CONRAD STAN / MICHAEL PETEPIECE STITTSVILLE SOUTH (AREA 6) WATER BALANCE NOVATECH FILE: 34 DAVID KARDISH (REIONAL) MARK PURCHASE (CAVANAUH). INTRODUCTION The following water balance evaluation has been prepared in support of a Draft Plan of Subdivision application for a portion of the lands within the Stittsville South (Area 6) Urban Expansion Area. The site is located between residential developments West Wind Farms to the north and Woodside Acres to the south, and is bounded by Stittsville Main Street to the west and the Faulkner Drain to the east. The proposed development will consist of a combination of single family detached units, townhouse units, and terrace homes, as well as two park blocks. A stormwater management facility is proposed at the southeast corner of the site, and will provide water quality and quantity treatment for runoff from the subdivision before discharging to the Faulkner Drain. 2. WATER BALANCE A water balance is used to characterize the relationship between precipitation, evapotranspiration runoff, and infiltration, with the objective of protecting natural features and groundwater resources. This exercise has been completed in order to determine whether the proposed development will have any adverse impact on the hydrologic characteristics of the Faulkner Drain. 2. Study Area For the purposes of this evaluation, water balance calculations have been completed for the site (34.65 ha), as well as the overall Faulkner Drain watershed upstream of Flewellyn Road (4.85 ha). Refer to Figure for an overview of the area and Figure 2 for soil information. Test hole information from the eotechnical Report (Paterson roup, January 3, 23) are attached. 2.2 Methodology The water balance has been prepared using 3-years (97-2) of precipitation and evaporation data measured at the Environment Canada Ottawa CDA rain gauge station. Water balance calculations are based on the following methodologies: M:\23\34\DATA\CORRESPONDENCE\MEMOS\WATER BALANCE\ WATER BALANCE - MEMO.DOCX

2 Thornthwaite and Mather (957) o o Actual evapotranspiration is based on measured evaporation data (converted to potential evapotranspiration using a cover coefficient) and the available water in the soil moisture storage zone. Water surplus (i.e. infiltration / runoff) is based on the amount of water that exceeds the water holding capacity of the soil moisture storage zone. Values for the water holding capacity were taken from the MOE SWM Planning and Design Manual (23) and are dependent on landuse and soil type. MOE SWM Planning and Design Manual (23) o Water surplus is differentiated into Infiltration and runoff using an infiltration factor, which is dependent on landuse, topography and soil type. The methodology portrayed by Thornthwaite and Mather (957) includes a soil moisture storage zone as it is a good indicator of the moisture conditions for the location since it incorporates antecedent conditions, the moisture supply, and the moisture demand for the current period. The analysis was performed on a watershed scale as it is assumed that on this scale lateral groundwater flow between catchments can be ignored. Measured evaporation data was used as the Thornthwaite and Mather (957) approach to calculating potential evapotranspiration is highly empirical as it is based on daily mean temperatures. The measured evaporation data was converted to potential evapotranspiration using a cover coefficient that is dependent on the vegetation type during the dormant and growing season. The cover coefficient for the growing season typically ranges between.7 and.3. For this analysis, an average cover coefficient value of. was used, which is typical for continuous hydrologic models and is representative of forest cover and cropland during the growing season. 2.3 Results The results of the water balance analysis are summarized in Table (site) and Table 2 (Faulkner Drain watershed upstream of Flewellyn Road). Supporting calculations and figures are attached. Table : Annual Water Balance Summary (Site) Scenario Precip. ET Water Surplus Infiltration Runoff Pre-Development 94 mm 577 mm mm mm mm 7.7 Post-Development 94 mm 57 mm mm mm mm 36.5 Difference (Post- Pre) mm -7 mm mm mm -. 7 mm 8.7 Table 2: Annual Water Balance Summary (Faulkner Drain upstream of Flewellyn Road) Scenario Precip. ET Water Surplus Infiltration Runoff Pre-Development 94 mm 569 mm mm mm mm 2.2 Post-Development 94 mm 566 mm mm mm mm 22.5 Difference (Post- Pre) mm -3 mm mm.4-9 mm mm.3 M:\23\34\DATA\CORRESPONDENCE\MEMOS\WATER BALANCE\ WATER BALANCE - MEMO.DOCX

3 Infiltration / roundwater Recharge The results of the water balance indicate that annual infiltration within the limits of the proposed development is anticipated to decrease by approximately under post-development conditions, based on the change in land use. However, the overall reduction in infiltration within the Faulkner Drain watershed upstream Flewellyn Road will be less than. Based on the surficial soil characteristics of the site, there are no significant groundwater recharge or discharge areas within the limits of the proposed development. As such, the proposed development is not anticipated to have any adverse impact on groundwater resources within the watershed. Baseflow The proposed development is not anticipated to have any significant impact on baseflow in the Faulkner Drain. The anticipated reduction in infiltration and evapotranspiration following development will increase the volume of annual runoff from the site. The proposed SWM facility can be designed to store a portion of the additional runoff to provide baseflow augmentation in the Faulkner Drain (if required). 3. CONCLUSIONS & RECOMMENDATIONS The water balance does not explicitly account for the proposed best management practices to promote infiltration, such as vegetated grass ditches, perforated rearyard catchbasin leads, directing roof leaders to grass surfaces, etc. The proposed SWM facility will serve as the primary means of providing water quality and quantity control. Where feasible, the use of lot level and conveyance BMPs will be considered as part of the detailed design of the subdivision to help offset the reduction in infiltration and increase in runoff from pre-development to post-development conditions. The primary considerations for BMPs will include long-term viability, maintenance considerations, and effectiveness. For example, infiltration type BMPs may be ineffective due to the type of soil and depth to bedrock. Yours truly, NOVATECH Conrad Stang, M.A.Sc., P.Eng Water Resources Engineer Michael Petepiece, P.Eng Project Manager M:\23\34\DATA\CORRESPONDENCE\MEMOS\WATER BALANCE\ WATER BALANCE - MEMO.DOCX

4 SHEA RD FAULKNER DRAIN WATERSHED UPSTREAM FLEWELLYN ROAD (4.85 ha) STITTSVILLE MAIN ST. PROPOSED DEVELOPMENT (34.65 ha) FERNBANK RD EXISTIN FAULKNER DRAIN FLEWELLYN RD LEEND CATCHMENT BOUNDARY OVERLAND FLOW DIRECTION Suite 2, 24 Michael Cowpland Drive Ottawa, Ontario, Canada K2M P6 STITTSVILLE SOUTH AREA 6 WATER BALANCE AREA OVERVIEW Telephone (63) Facsimile (63) Website :2, MAR FIURE

5 SHEA RD FAULKNER DRAIN WATERSHED UPSTREAM FLEWELLYN ROAD (4.85 ha) PROPOSED DEVELOPMENT (34.65 ha) EXISTIN FAULKNER DRAIN FLEWELLYN RD NOTE SOIL MAPPIN DISPLAYED FROM ONTARIO SOIL SURVEY ON7. F = NON-DEFERENTIATED FARMINTON SOIL Fg = FARMINTON SHINLY LOAM Fl = FARMINTON LOAM Fsl = FARMINTON SANDY LOAM Kg = KARS SANDY LOAM Ll = LYONS LOAM M = MUCK Ol = OSOODE LOAM Rs = RUBICON SAND Suite 2, 24 Michael Cowpland Drive Ottawa, Ontario, Canada K2M P6 Telephone (63) Facsimile (63) Website STITTSVILLE SOUTH AREA 6 WATER BALANCE SOIL OVERVIEW :2, MAR FIURE 2

6 Water Balance Calculations: Stittsville South (Area 6) - Site Pre-Development Drainage Area ha Landuse Water Holding Capacity of Watershed (HS"C") Land Cover Mature Forest mm Pasture/Meadow mm. Urban Lawns mm. Imp. Areas.9 mm. Average 272 mm.2 Infiltration Factor Classification Soils (Silty Sand / Silty Clay). Topography (Rolling Land). Infiltration Factor.52 Runoff Factor Evapotran spiration Infiltration Runoff Ottawa CDA (65976) 97-2 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual Total Precipitation (mm) P Potential Evapotranspiration (mm) PE Total Precip. - Potential ET (mm) P-PE Soil Moisture Storage (mm) ST Change in Soil Moisture Storage (mm) ΔST Deficit (mm) D Actual Evapotranspiration (mm) AE Water Surplus (mm) S Annual Infiltration (mm) I 75 Annual Runoff (mm) R 62 Post-Development Drainage Area ha Infiltration Factor Classification Water Holding Capacity Soils Topography Landuse of Watershed Land Cover Infiltration Factor (HS"C") (Silty Sand / Silty Clay) (Rolling Land) Mature Forest. 4 mm.8 Pasture/Meadow. 25 mm. Urban Lawns mm. Runoff Factor Imp. Areas 64. mm Average 45 mm Evapotran spiration Infiltration Runoff Ottawa CDA (65976) 97-2 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual Total Precipitation (mm) P Potential Evapotranspiration (mm) PE Total Precip. - Potential Evap. (mm) P-PE Soil Moisture Storage (mm) ST Change in Soil Moisture Storage (mm) ΔST Deficit (mm) D Actual Evapotranspiration (mm) AE Water Surplus (mm) S Annual Infiltration (mm) I 73 Annual Runoff (mm) R 333 Notes: ) Uses measured average monthly total precipitation and potential evaporation data (converted to evapotranspiration based on a cover coefficient of.). 2) Actual evapotranspiration and water surplus calculated using the Thornthwaite & Mather (957) methodology. 3) Runoff and infiltration calculated as per the MOE SWM Planning and Design Manual (23) methodology. 4) Impervious areas consist of rooftops, roads, and driveways. Annual Summary Scenario Precipitation Evapotranspiration Water Surplus Infiltration Runoff Pre-Development 94 mm 577 mm mm mm mm 7.7 Post-Development 94 mm 57 mm mm mm mm 36.5 Difference (Post- Pre) mm -7 mm mm mm -. 7 mm 8.7 Thornthwaite, C.W., and Mather, J.R Instructions and tables for computing potential evapotranspiration and the water balance. Centerton, N.J., Laboratory of Climatology, Publications in Climatology, v., no.3, p.85-3 Prepared by Novatech Date: 2/2/25 M:\23\34\DATA\Correspondence\Memos\Water Balance\ Water Balance - site.xlsx

7 Water Balance Calculations: Stittsville South (Area 6) - Faulkner Drain Upstream Flewellyn Road Pre-Development Drainage Area 4.85 ha Landuse Water Holding Capacity of Watershed (HS"C") Land Cover Mature Forest 2. 4 mm Pasture/Meadow mm. Urban Lawns mm. Imp. Areas 6.6 mm. Average 29 mm. Infiltration Factor Classification Soils (Varied)..7 Topography (Rolling Land)..7 Infiltration Factor.44 Runoff Factor Evapotran spiration Infiltration Runoff Ottawa CDA (65976) 97-2 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual Total Precipitation (mm) P Potential Evapotranspiration (mm) PE Total Precip. - Potential ET (mm) P-PE Soil Moisture Storage (mm) ST Change in Soil Moisture Storage (mm) ΔST Deficit (mm) D Actual Evapotranspiration (mm) AE Water Surplus (mm) S Annual Infiltration (mm) I 5 Annual Runoff (mm) R 94 Post-Development Drainage Area 4.85 ha Infiltration Factor Classification Water Holding Capacity Soils Topography Landuse of Watershed Land Cover Infiltration Factor (HS"C") (Varied) (Rolling Land) Mature Forest mm.4 Pasture/Meadow mm. Urban Lawns mm. Runoff Factor Imp. Areas 22. mm Average 89 mm Evapotran spiration Infiltration Runoff Ottawa CDA (65976) 97-2 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual Total Precipitation (mm) P Potential Evapotranspiration (mm) PE Total Precip. - Potential Evap. (mm) P-PE Soil Moisture Storage (mm) ST Change in Soil Moisture Storage (mm) ΔST Deficit (mm) D Actual Evapotranspiration (mm) AE Water Surplus (mm) S Annual Infiltration (mm) I 42 Annual Runoff (mm) R 26 Notes: ) Uses measured average monthly total precipitation and potential evaporation data (converted to evapotranspiration based on a cover coefficient of.). 2) Actual evapotranspiration and water surplus calculated using the Thornthwaite & Mather (957) methodology. 3) Runoff and infiltration calculated as per the MOE SWM Planning and Design Manual (23) methodology. 4) Impervious areas consist of rooftops, roads, and driveways. Annual Summary Scenario Precipitation Evapotranspiration Water Surplus Infiltration Runoff Pre-Development 94 mm 569 mm mm mm mm 2.2 Post-Development 94 mm 566 mm mm mm mm 22.5 Difference (Post- Pre) mm -3 mm mm.4-9 mm mm.3 Thornthwaite, C.W., and Mather, J.R Instructions and tables for computing potential evapotranspiration and the water balance. Centerton, N.J., Laboratory of Climatology, Publications in Climatology, v., no.3, p.85-3 Prepared by Novatech Date: 2/2/25 M:\23\34\DATA\Correspondence\Memos\Water Balance\ Water Balance - Faulkner Drain.xlsx

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10 54 Colonnade Road South, Ottawa, Ontario K2E 7J5 eotechnical Investigation DATUM round surface elevations provided by Thomas Cavanagh. BORINS BY Hydraulic Shovel DATE December 3, 22 P2853 TP ROUND SURFACE 2.56 Pen. Resist. Blows/.3m 5 mm Dia. Cone Water Content Compact, brown SILTY SAND with gravel, trace cobbles and boulders Compact, light brown SILTY SAND TP terminated on inferred bedrock surface at 2.28m depth (TP dry upon completion)

11 54 Colonnade Road South, Ottawa, Ontario K2E 7J5 DATUM BORINS BY round surface elevations provided by Thomas Cavanagh. Hydraulic Shovel DATE eotechnical Investigation December 3, 22 P2853 TP 2 ROUND SURFACE 2. Pen. Resist. Blows/.3m 5 mm Dia. Cone Water Content Compact, brown SILTY SAND with gravel, trace cobbles and boulders.4 9. TP terminated on inferred bedrock surface at.4m depth (TP dry upon completion)

12 54 Colonnade Road South, Ottawa, Ontario K2E 7J5 DATUM BORINS BY round surface elevations provided by Thomas Cavanagh. Hydraulic Shovel DATE eotechnical Investigation December 3, 22 P2853 TP 3 ROUND SURFACE 9.86 Pen. Resist. Blows/.3m 5 mm Dia. Cone Water Content Stiff, brown SILTY CLAY.56 TP terminated on inferred bedrock surface at.56m depth (TP dry upon completion)

13 54 Colonnade Road South, Ottawa, Ontario K2E 7J5 DATUM BORINS BY round surface elevations provided by Thomas Cavanagh. Hydraulic Shovel DATE eotechnical Investigation December 3, 22 P2853 TP 4 ROUND SURFACE 5.85 Pen. Resist. Blows/.3m 5 mm Dia. Cone Water Content LACIAL TILL: Light brown silty sand with clay, gravel, trace cobbles and boulders TP terminated on inferred bedrock surface at.m depth (roundwater infiltration at.9m depth)

14 54 Colonnade Road South, Ottawa, Ontario K2E 7J5 eotechnical Investigation DATUM round surface elevations provided by Thomas Cavanagh. BORINS BY Hydraulic Shovel DATE December 3, 22 P2853 TP 5 ROUND SURFACE 2.3 Pen. Resist. Blows/.3m 5 mm Dia. Cone Water Content Compact, brown SILTY SAND.7.3 TP terminated on inferred bedrock surface at.7m depth (High groundwater infiltration at.7m depth)

15 54 Colonnade Road South, Ottawa, Ontario K2E 7J5 eotechnical Investigation DATUM round surface elevations provided by Thomas Cavanagh. BORINS BY Hydraulic Shovel DATE December 3, 22 P2853 TP 6 ROUND SURFACE 2.25 Pen. Resist. Blows/.3m 5 mm Dia. Cone Water Content Compact brown SILTY SAND with gravel, trace cobbles LACIAL TILL: Compact to dense, grey silty sand with gravel, cobbles, boulders TP terminated on inferred bedrock surface at 2.59m depth (roundwater infiltration at.7m depth)

16 54 Colonnade Road South, Ottawa, Ontario K2E 7J5 eotechnical Investigation DATUM round surface elevations provided by Thomas Cavanagh. BORINS BY Hydraulic Shovel DATE December 3, 22 P2853 TP 7 ROUND SURFACE.52 Pen. Resist. Blows/.3m 5 mm Dia. Cone Water Content Compact, brown SILTY SAND with gravel, trace cobbles.9.52 LACIAL TILL: Compact to dense, brown silty sand with gravel, cobbles, trace boulders TP terminated on inferred bedrock surface at 2.29m depth (roundwater infiltration at 2.2m depth)

17 54 Colonnade Road South, Ottawa, Ontario K2E 7J5 eotechnical Investigation DATUM round surface elevations provided by Thomas Cavanagh. BORINS BY Hydraulic Shovel DATE December 3, 22 P2853 TP 8 ROUND SURFACE 2.74 Pen. Resist. Blows/.3m 5 mm Dia. Cone Water Content Compact to loose, brown SILTY SAND, trace gravel and cobbles..74 LACIAL TILL: Compact to dense, grey silty sand with gravel, cobbles, trace boulders TP terminated on inferred bedrock surface at 2.23m depth (roundwater infiltration at.m depth)

18 54 Colonnade Road South, Ottawa, Ontario K2E 7J5 DATUM BORINS BY round surface elevations provided by Thomas Cavanagh. eotechnical Investigation Hydraulic Shovel DATE December 3, 22 P2853 TP 9 ROUND SURFACE 5.3 Pen. Resist. Blows/.3m 5 mm Dia. Cone Water Content Loose, brown SILTY SAND.5 Weathered limestone BEDROCK.86 (TP dry upon completion)

19 54 Colonnade Road South, Ottawa, Ontario K2E 7J5 DATUM BORINS BY round surface elevations provided by Thomas Cavanagh. eotechnical Investigation Hydraulic Shovel DATE December 3, 22 P2853 TP ROUND SURFACE 6.88 Pen. Resist. Blows/.3m 5 mm Dia. Cone Water Content Compact, light brown SILTY SAND with clay, gravel, trace cobbles Weathered limestone BEDROCK TP terminated on bedrock surface at.9m depth (roundwater infiltration at.9m depth)

20 54 Colonnade Road South, Ottawa, Ontario K2E 7J5 DATUM BORINS BY round surface elevations provided by Thomas Cavanagh. eotechnical Investigation Hydraulic Shovel DATE December 3, 22 P2853 TP ROUND SURFACE Pen. Resist. Blows/.3m 5 mm Dia. Cone Water Content Loose, brown SILTY SAND with gravel, trace cobbles.5 Weathered limestone BEDROCK.7 (TP dry upon completion)