Stormwater Management Ponds

An engineered pond can settle suspended solids, detain frequent runoff for erosion control, reduce peak discharge for larger storms, and route flows above its normal operating range through a safe overflow. The approved drainage report defines each objective, storage volume, release rate, water level, and connection to the major and minor systems.

A forebay slows incoming water and captures coarse sediment before it reaches the main treatment cell. It localizes maintenance, protects the permanent pool, and can dissipate inlet energy. Harrowgate constructs the forebay berm, inlet apron, access route, and defined sediment-storage geometry so future cleanout can occur without rebuilding the pond.

Survey control is established outside the disturbed area, then used for subgrade contours, liner limits, pond bottom, shelves, berm crest, pipe inverts, outlet controls, and spillway. Harrowgate checks critical elevations before placing concrete or burying structures and provides an as-built survey that can be compared with the approved stage-storage design.

The geotechnical and hydraulic design determines liner need based on soil permeability, groundwater, permanent-pool requirements, nearby structures, and environmental setting. Liners can be compacted clay or synthetic systems. Harrowgate prepares the subgrade, protects penetrations, controls lift or seam quality, and prevents equipment damage during covering.

Where practical, clean drainage is diverted and sediment-laden runoff is treated through temporary controls before reaching permanent cells. Inlets are stabilized, exposed slopes are progressively seeded, and accumulated construction sediment is removed. Temporary measures remain until the upstream site is stable so permanent storage and outlet function are preserved.

Yes. We perform sediment removal, forebay reconstruction, outlet repairs, berm and liner work, spillway armouring, access improvements, and final grading and planting. The sequence includes temporary flow control and environmental limits so the live drainage system continues to operate while treatment volume and structure function are restored.

Typical records include as-built survey, compaction tests, liner quality results, concrete tests, pipe inspection, outlet dimensions, material tickets, planting records, and deficiency corrections. Harrowgate also documents final sediment removal and structure cleaning. The municipality or engineer may require additional commissioning and maintenance information before acceptance.