What kind/type/category of risks can be mitigated in a project?

Yes Indeed, I can add few of them: /1.
Sufficient Labor & professional team required to execute the project till successful Handing Over /2.
Proper logistics support to plan & provide all required installation material on time /3.
Full top management support to Project team to handle critical issues

There are three project constraint time ,cost & quality, both time and cost will effect the quality of the project, there are also other threat that can increase the risk of failure such as poor management,unrealistic deadline , insufficent budget , moving targets and poor planning, all of above factors will eventually effect the quality of project ,cost over run, missed deadline And disappointment to end user .
These risk or some of them can be eliminated to some extent by proper planning ,support from top management.

In projects there are two main types of assets (time and money).
and on the other hand there are some risks in projects which can be controlled and mitigated by allocating a limited amount of time and/or money.
lack of sufficient Human resources, Equipments, are examples of risks which are reparable by spending some amounts of time and/or money.

It depends on determination of risks factors and their analysis.
There are three types of risks; low(known-known), Medium(known-unknown) and High (unknown-unknown).
Mitigation of these risks depend on available resources; technology, time, finance, information, HR etc, Obviously everything goes to cost Example: Establishment of a chemical plant without hazardous environment control system is very risky.(high risk).
Total control system and emergency facilities mitigate the risk

Logistics, manpower, management, profitability, service, quality, reputation, brand value, and earnings quality are few of them.

All risks which can have a workable and achievable mitigation plan can be controlled so that the Cost, Schedule and Quality can still be maintained.

In addition to the listed risks, reporting & reviewing the progress at frequent intervals is very significant to adhere to time, cost, quality, without which all the toiled efforts will be of futile.