Crystal Lake is an important and environmentally sensitive resource that requires vigilance to keep it a high quality lake. The area around Crystal Lake that drains to the lake is called the Crystal Lake Watershed. The City has special requirements that regulate development and land use in the watershed, to protect the quality and quantity of water that reaches the lake.
If an improvement to your home or lot (house or garage addition, new garage, shed, patio, sidewalk, or new or widened driveway) increases the amount of impervious area, a trench drain may be required. City staff in the Engineering Division will determine if a trench drain is required but the following provides general guidelines.
If the additional square footage of impervious area for the improvement is less than 300 square feet, a trench drain is not required. If in the future there is additional impervious area added to the lot, it will be added to this impervious square footage and the cumulative number will be used to determine if a trench drain will be required.
If the impervious area is more than 300 square feet, a trench drain will need to be installed to compensate for the additional impervious area. In lieu of infiltration calculations provided by licensed Professional Engineer to determine how many feet of trench drain would be required, the City requires a minimum of 1 foot of trench drain per every 50 square feet of additional impervious area. A trench drain is required to be a minimum of 25 feet from a structure.
Here is the City's standard detail for a trench drain.