The locate is mandatory, free, and takes five business days
Requesting a locate before you excavate is a legal requirement in Ontario, not a courtesy. Ontario One Call states plainly that if you are planning to dig you must submit a locate request, and that it is the law. Requesting it costs nothing.
The timing matters. The request has to go in at least five business days before you dig. Infrastructure owners have five business days to respond to a single civic address request and ten for an advanced request, and Ontario One Call notes there is no guarantee a locate arrives within that window. A locate is then valid for at least sixty days.
What comes back is a set of instructions from each buried infrastructure owner, and those differ. There is no single hand-dig distance that applies to everything, so follow each owner's own instruction rather than a rule of thumb. This applies to a fence post and a tree pit as much as to a patio excavation.
You are not allowed to change your grading
The City of Ottawa's own landscaping guide is direct about this. You are not allowed to change the grading of a property. Water must follow approved drainage patterns and cannot be directed to neighbouring properties. Ditches cannot be altered, because they slow runoff, filter contaminants from surface water and reduce flooding risk.
In practice most Ottawa suburban lots were graded at construction to an approved plan, including the swale along the property line. Raising a bed, adding fill, building a shed in the swale or re-grading a back garden to make it flat are all changes to that plan, and they move water onto somebody else.
What you can do freely is restore the approved condition: extend downspouts so they discharge at least 1.8 m from the wall, remove the twenty years of accumulated mulch and soil that has raised a bed above the correct level against the foundation, and clear a swale that has been filled in. In a large share of damp Ottawa basements that is the entire repair. For anything beyond restoration, the Site Alteration By-law and the City are the route.
Trees, on your land and on the City's
City-owned trees are fully protected, and the City's guide sets out how: the critical root zone extends 10 cm from the trunk for every 1 cm of trunk diameter, tree protection fencing must be at least 1.2 m high and installed before work begins, no materials, objects or equipment may be placed in the root zone, and the ground level around the tree may not be changed.
On a 60 cm trunk that is a six metre radius. On a narrow inner-city lot it covers most of the front garden, which is why the tree question belongs in the design phase. Excavation, a new walkway, a window well or even a change in soil level inside that zone is a City conversation.
Private trees are protected too. The City's landscaping guide lists a tree permit as required for removal of a private tree over 30 cm diameter, and the Tree Protection By-law sets out the detail: in the urban area, a distinctive tree is commonly stated as one with a trunk diameter of 30 cm or more measured 1.3 m above grade on a lot of one hectare or less, with different thresholds on larger lots, for Planning Act applications and in the rural area. The urban threshold was lowered in recent years, so confirm your own case with the City rather than relying on a number you heard.
Permits a landscape project can trigger
A building permit for a retaining wall over 1 m, which also requires a professional engineer's design confirming compliance with Part 4 of the Building Code, with a guard where the drop exceeds 1.0 m.
An access permit and a road cut permit for driveway modifications, because the portion of your driveway inside the City right-of-way is the City's. A pool enclosure permit for a pool or a spa. A tree permit for a protected private tree. And the Site Alteration By-law for larger changes to grades or fill.
The City also restricts what may go into the right-of-way at all: hard landscaping there is limited to driveways and walkways, and river rock, stones, boulders and architectural or raised decorative features are not allowed. Artificial turf is not permitted in the right-of-way and does not count as soft landscaping anywhere, which matters because at least 50 per cent of the front lawn has to be soft landscaping.
What the ground is doing under all of this
Much of Ottawa is built on Champlain Sea clay, often called Leda clay, which swells when wet, shrinks as it dries and can lose much of its strength when it is disturbed, according to National Research Council work on the Ottawa area. It drains slowly, so surface water sits.
Frost reaches deep. The Building Code requires foundation depths as much as 1.2 m below grade in clay soils, which is a useful proxy for how far down frost matters here. That is why a pergola footing is a real excavation, why a retaining wall base goes deeper than the brochure detail, and why a buried drain line needs depth to keep working in February.
And the melt is concentrated. An entire winter's snowpack leaves in roughly a fortnight in late March, onto ground still frozen at depth. Drainage that works in a summer thunderstorm can be overwhelmed then, which is why March and April are the months Ottawa basements leak and why grading is the first landscape item rather than the last.