SERVICING, GRADING AND DRAINAGE PLAN - OAKVILLE

The Town of Oakville requires a Site Servicing, Grading and Drainage Plan to ensure that a proposed development is integrated with neighbouring lots, municipal services, and provides overall serviceability of the area. Our licensed Professional Civil Engineers prepare Grading and Servicing Plans in support of the Development Engineering Permit and Building Permit application to the Town of Oakville.

It is the responsibility of every lot owner in the Town of Oakville to maintain the lot’s grading and surface drainage. Any work carried out that changes the original approved grades by the Town of Oakville or the historically existing grades must not impair the lot’s ability to drain stormwater properly or create adverse impact to the adjacent properties, including the municipal right-of-way and the Town of Oakville's infrastructure.

In the Town of Oakville, the stormwater drainage is contained on every lot and is directed to an approved outlet, like the Town of Oakville's sewer or ditch, a rear lot catchbasin, or a creek, as in older areas of Oakville. Rainwater, snow melt, etc., flow to the above outlets via sheet flow across the lot or focused flow in shallow ditches called swales.

A private lot may also have upstream external stormwater drainage passing through from adjoining lots, as the intended design follows existing stormwater drainage patterns. It is the responsibility of lot owners to maintain the existing stormwater drainage pattern and not cause a blockage to upstream stormwater drainage.

As a result of landscape work, settlements due to natural soil consolidation over time, and the effects of nature such as root growth, mounding at trees and plant bases, buildup of leaves, etc., lot grading can become challenged.

Stormwater management measures are implemented to prevent negative impacts on every lot, adjacent lots, and the Town of Oakville's infrastructure. Development changes the pattern and amount of stormwater runoff as roof and hardened surface areas increase. While the impacts from one individual lot may seem inconsequential, cumulative impacts to the Town of Oakville's storm system have been demonstrated via modelling

carried out as part of the Town of Oakville's Stormwater Master Plan. Moreover, in some older areas, where drainage swales have subsided over time and the area is flat, additional stormwater runoff exacerbates any drainage issues. As such, new developments in the Town of Oakville must demonstrate that the existing drainage patterns are maintained or improved, and how the additional surface runoff is being mitigated. Changes that do impact lot grading and drainage could result in numerous issues, such as flooding, negative impact on adjacent lots, natural environmental features, and municipal infrastructures, costly repairs, negative feelings with the neighbours, and possible charges under the Town of Oakville’s by-laws.

The Town of Oakville requires a Grading and Servicing Plan in support of the following applications:

Development Engineering (DENG) Permits for

• Site Alteration for pools, landscaping, retaining walls, all teardown rebuilds, and additions for work outside the building footprint.
• Excavation for service connection road cuts (Contact Halton Region for sanitary and water connection permits)
• Driveway modification – new or modified curb cut
• Temporary Street Occupation for materials and equipment storage

Building Permit for 

• all teardown rebuilds only if the footprint is changing, 
• all additions or new structures

If the development site is subject to Site Plan Control, a Development Engineering Site Plan (DESP) approval or a Full Site Plan approval is required prior to issuance of a Building Permit.

Where a Development Engineering (DENG) Permit is required, a Development Engineering Permit Application (DEPA) is to be submitted to the Town of Oakville's Transportation and Engineering Department. A Pre-screening of the Development Engineering Permit Application (DEPA) submission will be carried out by the Development Permit Administrator at the Transportation & Engineering Department. Once the fee is received, the application is circulated for review. The applicant will then receive a notification on the required securities amount. Payment for the securities must be paid prior to issuance of the permit. Upon completion of the engineering and forestry review, the Development Engineering Clerk will check that the payment for securities has been paid.

Our licensed Professional Civil Engineers 

Prepare, stamp, and sign a Site Servicing, Grading, and Drainage Plan for inclusion with the required permit application;

Provide field review to ensure compliance with the Grading and Servicing Plan; and

Provide a final “Lot Grading Certificate” upon completion of the final grades.

Our licensed Professional Civil Engineers prepare Site Servicing, Grading, and Drainage Plans in accordance with

Town of Oakville Development Engineering Procedures and Guidelines, the Stormwater Master Plan, and the Site Alteration By-law,

and

Ontario Building Code Section 9.14.6.1.(1) to ensure that the proposed building will be located and the site grading has been designed so that it will not adversely affect adjacent lots.

Development Engineering Technologist (DET) in the Transportation & Engineering Department reviews the Site Servicing, Grading and Drainage Plan in accordance with the applicable Building Code requirements and provide comments under the Building Permit review are issued with the notification letter for the Building Permit.

The review of tree protection and removal are completed outside of the Building Permit process by the Town of Oakville's Forestry Department. Forestry will contact the applicant directly, requesting the required documents.

Applicants are not permitted to remove/impact trees without Forestry approvals, as per below

i. Trees inside building footprint are exempt

ii. Removal of trees outside of building footprint (1m of foundation) requires a Private tree removal permit [Town of Oakville's Private Tree By-law (2017- 038)]

iii. All trees in right-of-way, town property or woodlot behind property require a Tree protection permit [Town of Oakville's Tree By-law (2009-025)]

iv. All tree protection during construction as per the Town of Oakville’s Tree Protection During Construction Procedure 

If a DENG permit is required, the Forestry Department will coordinate the two reviews.

The following provides for a detailed procedural policy for any form of lot grading within the Town of Oakville, on a lot-specific basis.

A detailed lot grading plan must accompany all building permit applications to the Town of Oakville. Building permits will not be issued by the Town of Oakville until the Development Services Section is satisfied with the lot grading plan.

Information Required by The Town of Oakville on Lot Grading Plans
Plot plans shall be submitted as one lot per sheet at a scale of 1:200. Sheet size of 24 × 36 inches Arch D is preferred; 8.5 × 14 inches or 11 × 17 inches is acceptable if all required information fits on the page at the 1:200 scale.

• A key plan with a north arrow is required in the upper right-hand corner of the sheet.
• Provide a title block with the name of the builder/developer/subdivision, registered plan number, architect/designer company, scale of drawing, and date of preparation.
• Provide the as-built location and elevation of storm, sanitary, and water services
• Elevation of culverts, drainage ditches, and sidewalks
• Location of approved erosion and sedimentation controls
• Location of sump pump, discharge point, downspouts, and any dry wells
• All hard surfaces, patios, and walkways
• Location of the air conditioning unit
• Provide the existing elevations as per the topographic survey, indicating existing buildings, drainage patterns, and finished first-floor elevations for all buildings on adjacent lands.
• Indicate the surface runoff for all adjacent and proposed lots using arrows to show the direction of flow and swale locations, length, and slope percentage.
• Indicate the house type and elevations of the finished first floor, top of foundation wall, basement floor, underside of the footings, and service lateral invert at the property line.
• Indicate the elevations at the lot corners, landings, garage slab, and all entrances (indicating the number of risers), the existing roads, and catch basins. Refer all elevations to a geodetic Town benchmark.
• Indicate the location, length, and percent slope of proposed driveways.
• Provide complete details of proposed retaining walls and noise/privacy fencing.

Lot Grading plans shall be submitted to the Town of Oakville at a scale of 1:200. Sheet size of 24 × 36 inches, Arch D is preferred; 8.5 × 14 inches or 11 × 17 inches is acceptable if all required information fits on the page at the 1:200 scale.

A key plan with a north arrow is required in the upper right-hand corner of the sheet.

Provide a title block with the name of the builder/developer/subdivision, registered plan number, architect/designer company, scale of drawing, and date of preparation.

Provide the as-built location and elevation of storm, sanitary, and water services

Elevation of culverts, drainage ditches, and sidewalks

Location of approved erosion and sedimentation controls

Location of sump pump, discharge point, downspouts, and any soakaways

All hard surfaces, patios, and walkways

Location of the air conditioning unit

Provide the existing elevations as per the topographic survey, indicating existing buildings, drainage patterns, and finished first-floor elevations for all buildings on adjacent lands.

Indicate the surface runoff for all adjacent and proposed lots using arrows to show the direction of flow and swale locations, length, and slope percentage.

Indicate the house type and elevations of the finished first floor, top of foundation wall, basement floor, underside of the footings, and service lateral invert at the property line.

Indicate the elevations at the lot corners, landings, garage slab, and all entrances (indicating the number of risers), the existing roads, and catch basins. Refer all elevations to a geodetic Town benchmark.

Indicate the location, length, and percent slope of proposed driveways.

Provide complete details of proposed retaining walls and noise/privacy fencing.  

Grading and Drainage Terms and Definitions

The Town of Oakville and the construction industry use many terms that are unique to describing and detailing how grading and drainage work. 

Apron swale

An apron swale is a swale that is formed across the rear yard of a front draining lot, approximately 5 m from the house, which collects water from the rear yard and directs it to the side property line swales.

Catchbasin

A catchbasin is a concrete chamber in the ground with a slotted iron lid which allows surface water to be collected and then directed into a storm sewer. They may be found along the edges of a road or in rear corners of private yards.

Focused flow

Surface drainage that has been collected or concentrated in one area or outlet.

Grade

Grade typically indicates the level (height) of the ground. It can be measured from a known point or in comparison to the ground level at a previous/future time.

High point

Is a location on the ground from where water flows away. Typically, it is a starting point of a swale or the top of a sloped area.

Property line swale

A swale located along a property line, where half of the swale is located on each abutting property

Rear to front drainage

Rear-to-front drainage is where the rear property line is the high point. All surface drainage on the property flows to the front of the property via an apron swale in the rear of the property that directs the water around the house to the side lot swales (located on the property line) on either side of the house and then out to the street.

Split drainage

Split drainage is where a high point is established at approximately the mid-point of the property. The surface drainage from the front of the property drains toward the road, and the rear of the lot drains towards the rear lot line, where a swale collects the water and directs it to an outlet. e.g., a rear year catchbasin or adjoining property line swale.

Sheet flow

Sheet flow refers to surface drainage that is not collected or focused but allowed to flow over a wide area in a specific direction.

Slope

The amount of inclination or angle up or down that a surface (the ground) has from a flat or horizontal surface.

Surface drainage

Surface drainage is the removal of excess surface water as a result of rain, snow melt, downspout discharge, etc., by the use of sloped ground and swales.

Swale

A swale is a shallow ditch approximately 150 to 300 mm in depth and typically 1 to 2 m in width and having side slopes no greater than 3:1. 

Site Grading and Site Servicing Items

Existing spot elevations within the project site and along the property limits - lot line elevations. Minimum of 5m outside the property boundaries, on abutting public streets, and at a maximum of 10m intervals within the property. Include the finished floor elevation and finished floor door sill elevations of adjacent properties.

Arrows indicating the direction of surface drainage on all proposed paved, granular, and grassed areas and the slope - between 2-5% for softscape and 1-5% for hardscape, as per Development Engineering Procedures and Guidelines.

Proposed spot elevations: At all high/low points of the side yard swales, top and bottom of slopes, all changes in gradient, building corners, building entrance, etc. At the top and bottom of retaining walls, bottom elevations on both sides of the wall shall be provided. Provide cross sections to better illustrate design intent, as required. Retaining walls that are not designated structures require a site alteration permit, designed as per the Development Engineering Procedures and Guidelines. Any retaining walls proposed along or near lot lines will require a cross-section. The retaining wall to be a minimum of 0.30m away from the property line within the subject site. Wall ends to be tapered to a maximum of 0.15m in height.

For tear-down/rebuilds and additions, show house siting elevations: Basement slab elevation(s), garage slab elevation(s), finished floor

elevation of the ground floor, and entrance to all buildings, elevations of the underside of footings - identify all footing levels with different

elevations and top of foundation wall elevation. Where the top of the foundation wall elevation changes or a reverse veneer is used, the limit of the sections and the different top of foundation wall elevations must be identified.

Proposed swales designed as per Development Engineering Procedures and Guidelines - if different, cross details to be provided for review. Swales must be designed to convey surface runoff away from the subject site without spilling onto adjacent properties. Infiltration galleries without an overflow outlet are not approved ultimate outlets for surface runoffs.

Include proposed locations and direction of flow for proposed downspouts. Downspouts must be designed in accordance with the Development

Engineering Procedures and Guidelines.

Details on proposed vehicular entrances to the subject property, including elevations at the garage and property line, driveway slope between 1-7%. Driveway elevation at property line must match existing elevation. Slopes of driveway within private property and Town R.O.W. do not have to be the same.

Proposed and existing sheds, cabanas, structures, pool equipment, etc.

For tear-down/rebuilds, show proposed service connections, including the mainline invert and obvert, invert of service connection at property line, identification of pipe length from mainline to property line, material, diameter, and slope. Invert of proposed service connection shall match the obvert of the existing mainline sewer. Distance to the closest MH must be scalable on the drawing or dimension provided. Provide pipe elevations at crossings between mainline sanitary/storm sewers and proposed sanitary/storm connections.

Demonstrate that the site’s drainage design does not have an adverse impact on the subject site and adjacent properties. Identifying any existing swales, ditches, rear yard catch basins, culverts (including size), creeks, watercourses, remnant channels, and drainage easements, overland flow routes, complete with elevations, inverts, and flow arrows indicating the surface drainage direction. Provide Stormwater Management Report, where applicable, to comply with the Town of Oakville’s Stormwater Master Plan.

Show the location of proposed sump and/or ejector pumps for storm and/or sanitary, respectively. Indicate if the sump pump is to discharge to the storm sewer

or to the splash pad at grade. The Town of Oakville’s preferred approach is to discharge foundation drains to grade with a splash pad, approximately 1.5m (5ft) from the foundation.

Erosion and sediment control measures are to be used during construction (OPSS 805). Silt fence should be placed at the limit of construction and

away from shared property lines (OPSD 219.130 (heavy duty), OPSD 219.110 (light duty)).

Locations of any regulatory flood lines or development limit lines (i.e., setback and slope stability limits).

The following criteria apply to overall residential subdivision drainage control and lot/site-specific drainage design in Oakville. Lot-specific elevations shall conform to the approved subdivision control plan.

Grading and drainage shall provide positive surface drainage directed away from any buildings toward lot line swales, graded to drain to an acceptable outlet.

Drainage shall be directed to an outlet location that is deemed acceptable by the Town of Oakville. Where a split or front-to-back grading design is utilized to outlet surface drainage and runoff will or is likely to drain onto another property, a private or municipal rear lot catch basin is required to be constructed to collect the water and outlet it to the storm sewer or municipal ditch, or other suitable outlet. Easements may be required. Should this not be feasible, other approved methods may be proposed. On older infill residential lots, pass-through grading (a portion of a higher lot drains through a lower lot) is not permitted unless specific permission from the Town of Oakville is obtained.

All swales shall have a minimum depth of 150 mm, 3H:1V (horizontal to vertical) slopes on both sides, and a minimum slope of 2.0% (or 1% slope with subdrain exiting within the property) for a maximum length of 60m before outfall to sewer, creek, or municipal road/block.

Window wells, where required, shall be indirectly connected to the weeping tile system using 100 mm drainpipe filled with 19 mm clear stone.

All downspouts shall discharge onto approved sodded areas using splash pads for erosion control. Direct connection of the downspouts to the storm system must have prior approval from the Town of Oakville (high-density). The location of the discharge is not to interfere with access or pose a safety hazard.

For sites with no municipal services: Location of septic tanks, outline of tile beds, wells, and holding tanks for fire-fighting shall be shown.

Details on proposed vehicular entrances to the subject property, including: Show limit of garage door opening; Identify the size of garage (1-, 2-, or 3-car); Provide dimensions of driveway apron on private property as per zoning by-law 2014-014 Section 5.8.2 and on Town Right of Way as per Town of Oakville Driveway permit procedure. Driveway width transition to be on private property and straight edges for the Town Right of Way driveway apron. Ensure minimum offset of 1.0m to boulevard furniture - light and utility poles, pedestals, transformers, hydrants, mailboxes, trees, bus shelters, and street furniture within Town Right-of-Way to remain unchanged. Existing sidewalk elevation not permitted to be altered to accommodate the driveway. If relocation of utility furniture is required, approval from the appropriate agency(s) must be obtained before DEPA approval.

Walkway location, width, setback from driveway, and Walkway-Driveway access point width. One walkway access may be connected to the side of a

driveway. The maximum width of the walkway access at the connection point shall be 1.8m. The walkway shall terminate at the municipal sidewalk, private side, or property line if there is no sidewalk. Curb cuts in the walkway are prohibited.

Driveway border/edging location, width, and elevation - all borders adjacent to the driveway are part of the total driveway width. Raised borders within the right-of-way are prohibited. Maximum border width is 0.3m.

Proposed length of curb modification, cut, and/or fill.

Driveway setback dimension from property lines. A driveway crossing a frontage or flankage lot line on a corner lot shall be located a minimum of

15m from the point of intersection of the front and flankage lot lines or where the lot lines do not intersect, the point of intersection of the projection of the front and flankage lot lines, measured along all points of the driveway. Should the lot not be wide enough for the provisions noted above, the following calculation applies: Measured from the inside lot line, the required inside setback, plus the width of the driveway, plus 1m, Culvert length, diameter (min. 300mmØ), material (new; corrugated/ ribbed steel, PVC “Big O” or HDPV pipe), and invert elevations. Indicate on the drawing that new culverts are to be installed by the owner at the owner’s expense.

Show catch basin sediment traps and design details, if there are catch basins within proximity of the site. Note on drawings that catch basins are to be fitted with a sediment trap at each catch basin.

Show location of temporary gravel access pad (mud mat) at the entrance of house construction activities with a minimum 300mm depth of 75-100mm

diameter of clear stones. Size the mud mat to suit the site. Include mud mat and ditch details on the drawing. If the existing driveway is used as construction access for mud tracking purposes, indicate so on the plan.

Setback dimensions - distance from proposed works to property lines.

Geodetic survey datum, derived from Town of Oakville benchmarks - Benchmarks used must be identified on the Grading Plan. Topographic Survey of existing elevations, grading features, slopes, berms, swales, trees, etc. (Topographic survey must be completed no longer than 1 year before submitting the Grading Plan). Topographic Survey information is superimposed onto one drawing with proposed information. A separate topographic survey drawing is not required to be submitted.

Existing house footprint on the subject property and adjacent property(s). Existing spot elevations within the Town Right-of-Way (minimum every

10m); and slope gradients at all critical locations (Including road center lines; vehicle accesses and driveways, ramps, parking lots, both edges of pavement, curb lines or sidewalks; swales, ditches, culverts, grassed areas, etc.).

Maintain or reinstate a minimum of 0.30m strip of sod/river rock and filter cloth around the perimeter of the site wherever it abuts adjacent properties. If grades are disturbed, restore elevations to match adjacent property at the property line.

A minimum of 0.15m is provided between the highest finished grade adjacent to the house and the top of the foundation wall elevation.

If applicable, show tree protection fence, matching the TPZ approved by the Town Parks Forestry Department. Drawing shall include Oakville’s tree

preservation standard drawing. Include any tree preservation note as required by Parks Forestry on the Grading Plan. Tree information, such as

species, size, etc., is not required on the grading and servicing plan.

Location, elevation, and dimensions of proposed pool, hot tub, or pond. Add note “Pool water to be pumped using a portable pump to the front

Municipal Boulevard.”

Existing features on the property (i.e., downspouts piped underground, retaining walls or gardens blocking swales, etc.) that may not meet with

Town of Oakville standards that impact grading and drainage as a result of the proposed work activities shall be identified and corrected by the homeowner prior to a permit being issued or corrected in conjunction with the permit.

Provide a hydraulic grade line analysis to demonstrate no flood risk for a 100-year event in the case of a reverse slope driveway. The major system capacity also needs to be considered for a reverse slope driveway.

For tear-down/rebuilds, show all existing and proposed servicing infrastructure within the road allowance. This includes, but is not limited to:

Manholes, storm and sanitary sewers, water mains (include identification of all pipe material, diameter, slope, direction of flow and manhole inverts), catch basins, valve boxes and chambers; Existing above and underground utility features within the boulevard; including but not limited to gas meters, light poles, utility poles, pedestals, transformers, and all underground and overhead utility lines (hydro, gas, bell, cable). Plan and Profile Drawings and As-Built Drawings can be used as reference only.

For tear-down/rebuilds, show location and details of any existing service connections to Town and Region infrastructure, as per locate records. Indicate whether or not they will be decommissioned. If the existing sanitary, water, and/or storm service connections are proposed to be reused, the existing invert elevation at the property line must be obtained and shown, along with pipe size and type of material. Note on the drawing that the invert elevation at the street line is verified by the licensed Professional Civil Engineer.

The water box must be located outside of the driveway.

Provide a minimum 1.0m horizontal offset between proposed and existing service connections.

Where possible, place proposed storm and sanitary connections in a common trench, with a 0.5m horizontal separation.  

 Yard and Driveway Slopes

• All yard surfaces, front and rear, shall have a minimum slope of 2.0%.
• Rear yards are to have a maximum grade of 5.0% for a minimum apron length of 5 m from the rear face of the dwelling.
• The maximum slope allowed on any yard surface side, front, and rear shall be 3H:1V.
• Driveway slopes shall be a minimum of 1.0% and a maximum of 7.0%.
• There shall be a 0.6 m wide path at a 2.0% slope away from the foundation around one side of the building, except where side yard setbacks from lot lines do not permit. This flat area allows for a walkway to access the rear of the house.

Where required by site plan or site alteration, a Stormwater Management Report /Brief is required.

Potential low-impact development (LID) best management practices (BMPs)supported by the Town of Oakville include, but are not necessarily limited to:
• bioretention areas and bioswales
• vegetated filter strips
• enhanced grassed swales
• permeable pavements (asphalt, concrete, paving, and stones)
• soak-away pits, dry wells, and infiltration chambers
• exfiltration pipes
• prefabricated modules (including soil retention cells) and tree pits
• green or living roofs
• rainwater harvesting and reuse.

 Stormwater Management practices across Ontario have evolved from more conventional end-of-pipe techniques to a suite of practices commonly referred to as low impact development (LID) best management practices (BMPs) to reduce and treat the volume of stormwater runoff prior to discharge to receiving systems.   

The Town of Oakville encourages the use of low-impact development (LID) facilities to meet both quantity and quality control criteria for sites. Low-impact development (LID) facilities also provide additional benefits for water balance and erosion/sediment control. Low-impact development (LID) best management practices (BMPs) can be used as part of a treatment train approach to achieve stormwater management objectives. 

Low impact development (LID) facilities will be credited for quality and water balance control, if they are sized and designed properly, but will not be credited for quantity flood control when sizing downstream infrastructure.  

Low impact development (LID) facilities are to be sized to retain runoff occurring from a 25mm event per the recommendation of the Town of Oakville's Stormwater Master Plan.   

Low-impact development (LID) facilities should not be oversized to overcontrol entire sites; infiltration facilities should be sized up to a maximum of 90% of the average annual runoff volume for the contributing area. .

 Sump pumps shall discharge via pipe directly to a storm sewer where available and provided there are no capacity issues. A backflow preventor at the property line and an air gap are to be provided. A sump pump must be included on the grading plan. 

Where a storm sewer does not exist, sump pumps shall discharge to grade according to the following Town of Oakville's discharge outlet criteria:
• The discharge pipe must outlet to the front of the building; outletting to the side or rear yard is not permitted.
• Outlet must maintain a minimum 1 m setback from buildings and direct discharge away from buildings.
• Outlet to concrete splash pads and then to pervious grassed or landscaped areas for infiltration.
• Outlet must be a minimum of 1.8 m from the roof leader/downspout discharges.
• Discharge must be contained on site with no negative effect on neighbouring properties.

Where an existing basement excavation (underside of footings) is lower than the seasonally high groundwater level, sump pumps may run continuously and, therefore, are not acceptable to the Town of Oakville.

Foundation intersection with high groundwater table is strongly discouraged by the Town of Oakville.