Drainage Contractor

Harrowgate installs storm sewers, catch basins, maintenance holes, subdrains, trench drains, roof-drain connections, culverts, swales, oil-grit separator interfaces, underground storage, infiltration components, outlet controls, and erosion protection. We also self-perform and manage excavation, bedding, backfill, testing, grading, pavement, and landscape restoration.

Survey control is established from the approved benchmark and profile. Harrowgate checks the downstream tie-in, bedding elevation, each pipe length, structure inverts, and final rims as work advances. Recorded as-built elevations are compared with the design before surface restoration. A visual fall or excavator display does not replace survey verification.

Settlement follows weak founding material, disturbed base, poor compaction around the structure, utility trench movement, incorrect adjustment units, or heavy loading before support is complete. Harrowgate removes unsuitable material, builds the specified base, compacts evenly, coordinates frame adjustment with final pavement, and protects structures from traffic during construction.

Harrowgate measures and confirms the operating condition, then implements the approved diversion, bypass pumping, plug, staging, monitoring, and emergency response plan. Flow control is established before opening the system. Weather forecasts, upstream sources, pump capacity, power, discharge point, standby equipment, and access remain actively managed through the tie-in.

The owner’s contract identifies the governing documents. Common Ontario references include OPSS 410 for pipe sewers, OPSS 407 for maintenance holes and catch basins, OPSS 514 for trenching and backfill, associated OPSD drawings, and municipal amendments. Harrowgate confirms the exact editions and owner standards before procurement and construction.

Testing follows pipe material, owner, and contract requirements and includes combinations of survey, visual inspection, video inspection, leakage testing, deflection testing for flexible pipe, structure inspection, cleaning, and functional flow checks. Harrowgate tracks each result by pipe run and structure, corrects deficiencies, and updates as-built records before turnover.

Yes. Harrowgate surveys the existing surface and drainage network, identifies whether the cause is grade, inlet elevation, blockage, settlement, pipe capacity, outlet control, or pavement deformation, and executes the approved correction. Work includes catch basin adjustment or replacement, pipe repair, subdrains, grading, granular reconstruction, and paving.