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Exhibit C <br />GRAVEL BASIN MAINTENANCE PLAN <br />142 Warwick Street, Redwood City <br />APN 052-072-190 <br />Date: November 2, 2021 <br />Property Owner: Ping Guo <br />Project Coordinator: Ping Guo <br />428 Casita Way <br />Los Altos, CA 94022 <br />650-996-1454 <br />pingguoca@gmail.com <br />SUMMARY OF STORMWATER SYSTEM <br />The project consists of two Drainage Management Areas (DMAs), containing two stormwater <br />treatment facilities which allow the stormwater to flow into two underground gravel basins. <br />DMA 1: DMA 1 covers an area of 1672 square feet of landscaped land, with no <br />impervious surfaces, in the back yard. The stormwater sheet flows across the property on <br />nearly level land, with slight grades down to a catch basin and the grate above the gravel basin. <br />The gravel basin is 4.1 X 4.1 feet wide by 2 feet deep. <br />DMA 2: DMA 2 covers an area of 5070 square feet, consisting of roofs for the two <br />proposed buildings and landscaped land, in the front and side yard. The stormwater <br />is piped from the roofs and the driveway to the gravel basin. The stormwater from <br />landscaped areas sheet flows across the property on nearly level land, with slight grades down <br />to a catch basin and the grate above the gravel basin. The gravel basin is 6 X 6 feet wide by 5 <br />feet deep. <br />ROUTINE MAINTENANCE & INSPECTION <br />The following steps apply to both gravel basins. <br />• Remove debris from 12" X 12" area drains and from top of cobbles under metal <br />grate. (Perform as needed, after storm event.) <br />• Check one -inch pipes for clogging: clear if clogged. (Perform as needed, after <br />storm event.) <br />• Remove leaf debris from tops of grates. (Perform as needed, after storm event.) <br />• Check for erosion around gravel basins. (Perform on an annual basis.) <br />• Keep areas adjacent to the gravel basins free from excessive vegetation. <br />(Perform on an annual basis.) <br />• Keep roof gutters clear. (Perform as needed, after storm event.) <br />PROHIBITIONS <br />Trees and other large vegetation shall not be planted near gravel basins, to prevent <br />damage. <br />ATTY/AGR.2021.319/Baosheng Cai and Chenchen Xie (Page 10 of 11) <br />