How about using a subsurface drainage sheet to improve the drainage of your garden? (This is a completely unused item, but the box has been opened, so it's discounted by 5000 yen from the original price of 13750 yen.) Sheet Size: Thickness 10mm x Width 30cm x Length 10m Compared to the PVC subsurface drainage pipes often used for underground drainage in grounds, experiments have shown that this sheet drains more water and dries faster. See the manufacturer's website below: Improve drainage in gardens with poor drainage! By digging holes in the ground and laying the sheet with a slope, rainwater drainage is promoted. It is ultra-lightweight and can be easily cut with scissors, making it a soil improvement material that can be used in general households. 【Features】 Adaptable to deformed ground... High flexibility, no worries about bending or cutting. High drainage capacity... Exhibits drainage effects for both rainwater from above and spring water from below. High-performance double-sided drainage type... Due to the specially processed, non-clogging filter and the hardened vinyl chloride core material with excellent pressure resistance, high drainage capacity is maintained for a long period. Easy installation... No special techniques or joints are required. It is ultra-lightweight, making it easy to handle and shortening installation time. Cost reduction... Can be installed at 1/2 to 1/5 the cost compared to conventional natural aggregates such as sand. 【Main Installation Locations】 Gardens, golf courses, grounds, parks, embankments, etc. It is also used as an alternative to sand mats and sand filters that require high-quality sand and crushed stone. 【Installation Quantity目安 (Estimate)】 It depends on the environment of the installation location and the degree of drainage deficiency, but as a guide, install at intervals of 2-3m. ＜Before Installation＞ ・Cut with scissors, not a cutter. ・When cutting, cut the recessed part of the uneven core material. 【Installation Method】 1. Cut the "Ultra-Lightweight Drainage Sheet" with scissors to the length of the installation location. 2. Be sure to create a slope (gradient) at the installation location, making the deepest part about 30cm, and secure a water escape at the lowest point (the end of the slope) for installation. 3. Bury the installed "Ultra-Lightweight Drainage Sheet". 【Specifications】 Size: Thickness 10mm x Width 30cm x Length 10m Manufacturer's Website: Search for Kokubu Green Farm Ultra-Lightweight Drainage Sheet. I purchased it on Rakuten but decided to sell it because the drainage issue was resolved with exterior construction. Search Keywords: Drainage, Subsurface Drainage, Permeable Sheet, Field, Subsurface Drainage Pipe, PVC Pipe