Applying deep layers of fresh mulch annually before the growing season will reduce the occurrence of weedy plant growth . Fresh mulch also improves the aesthetic overtime as older mulch breaks down and changes color . Over the growing season , overgrowth should be removed as necessary to maintain the aesthetic appearance of the site and prevent competition between plants . At the end of the growing season , dead plant material can be removed to promote healthy plant growth in the following season . The earthen works should be maintained by replacing and reinforcing any soil that ' s been lost to erosion or animal activity over the years . Overall , maintenance varies by site and the overall desired appearance of the site . Installed pipes should be checked every 4-5 years to note any issues with clogging or poor drainage .
In addition to maintenance , monitoring of the bioretention area ’ s efficacy is encouraged . A simple method to determine efficacy is to visit the bioretention area directly after a rainfall event and record the length of time it takes for the collected water to fully drain . Charleston County recommends that bioretention areas are fully dewatered within a 24 to 48-hour period depending on dimensions , filter media and the underdrain system ( 2017 ). For advanced methods , a well point can be driven 4 feet into the soil away ( avoiding any drainage pipes ) and outfitted with a Levelogger to continuously track drainage . The data gathered from the Levelogger should be compensated with barometric pressure readings . Additional maintenance guidelines are found in Table 5 below from the Charleston County Stormwater Permitting Standards and Procedures Manual .
Table 5 . Bioretention maintenance requirements ( Charleston County , 2017 )
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NATURE-BASED SOLUTIONS MANUAL FOR KIAWAH ISLAND