Yard drainage survey

About this template

French drains and dry wells for a wet yard: each trench's excavation, stone, geotextile and drop to its outlet; each dry well's water to hold from the area it drains and your design rain, its pit over the stone's voids, its footprint and the hours the soil takes to empty it.

Guide and sources

Walk the wet spots with the client: one row per stretch of french drain, with its length, the trench's width and depth and the stone layer; one row per dry well, with the roof or yard area that drains to it. The sheet gives the excavation, the stone and the geotextile for each trench, the drop to its outlet for the slope you choose, and for each well the water it must hold and the pit that holds it.

A dry well holds a design rain over the area it drains: the Quebec guide stores 5 to 25 mm (0.2 to 1 in) of rain from the roof, New Hampshire's homeowner guide a 1-inch storm. The stone leaves 35 to 40 % of the pit to water (Quebec guide; 30 to 40 % for CVC and TRCA), so the pit is the water over its voids; spread over the depth you choose, that is its footprint. Keep it at most about 1.5 m (5 ft) deep, its bottom 1 m above the water table or rock, and 4 m (13 ft) from any foundation.

Test the soil where the pit goes (New Hampshire: fill a hole twice, read the drop in 15 minutes, multiply by 4): the sheet then gives the hours the full pit takes to empty, to compare with the 48 hours the Quebec guide and CVC design for. Below 15 mm/h (0.6 in/h), a loam, the Quebec guide says no infiltration pit. Request a locate before digging and ask the municipality where the water may go. The client's report shows the drains and wells and their size; the stone, geotextile and design figures stay in your team's report.

Sources

• ADS, product catalog Manufacturer dataADS Water Management Product Catalog (single wall pipe and geosynthetics), Advanced Drainage Systems, catalog read 2026-10-14 (no date printed). Checked Oct 14, 2026
• Oregon State Extension, drywells Trade associationLow-impact development fact sheet: drywells (EM 9200), Oregon State University Extension Service, EM 9200, May 2018. Checked Oct 15, 2026
• IRC 2021, R401.3 CodeInternational Residential Code 2021, R401.3 Drainage (as adopted in Colorado), International Code Council (read in a state adoption on UpCodes), 2021. Checked Oct 14, 2026
• New Hampshire homeowner's guide, dry well GovernmentNew Hampshire Homeowner's Guide to Stormwater Management: dry well, New Hampshire stormwater guide for homeowners (copy hosted by NH LAKES), dry well chapter, p. 21 and 22. Checked Oct 15, 2026
• 811 (US) Trade association811 Before You Dig, Common Ground Alliance, current page. Checked Oct 7, 2026
• NBC 2020, 9.12.4.1 CodeNational Building Code of Canada 2020, 9.12.4.1 Backfill, National Research Council Canada, 2020 (Quebec: Code de construction, chapitre I, in force 2025-04-17). Checked Oct 14, 2026
• CVC and TRCA, LID guide (soakaways) GovernmentLow Impact Development Stormwater Management Planning and Design Guide, 4.4 Soakaways, infiltration trenches and chambers, Credit Valley Conservation and Toronto and Region Conservation Authority, version 1.0, section 4.4. Checked Oct 15, 2026
• Quebec stormwater guide GovernmentStormwater management guide (Quebec), Quebec ministries of the environment (MDDEFP) and municipal affairs (MAMROT), 2011, chapter 11, pp. 11-20 (table 11.13) and 11-25. Checked Oct 15, 2026
• Info-Excavation Trade associationDemande de localisation : questions fréquentes, Info-Excavation, current page. Checked Oct 7, 2026