All erosion and sedimentation controls are to be in place prior to the start of construction. Measures used to collect and convey stormwater on any site shall be designed to meet the following minimum performance standards:
A. Prevent erosion damage and satisfactorily convey and control the rate and volume of discharge of stormwater to waters of the commonwealth.
B. When soil conditions are suitable, require runoff control measures to infiltrate the stormwater into the ground to aid in the recharge of groundwaters and the preservation of baseflow.
C. Control/accommodate not only the anticipated peak discharge from the on-site disturbed area, but also the existing runoff being contributed from all land at a higher elevation in the same watershed.
D. Maintain the adequacy of the natural stream channels. Accelerated bank erosion shall be prevented by controlling the rate and velocity of runoff discharged to these watercourses so as to avoid increasing the occurrence of streambank overflow.
E. Preserve the adequacy of existing culverts and bridges by suppressing the new flood peaks created by the new earth disturbances and new increased imperiousness.
F. If, in the course of preparing or reviewing the stormwater management plan, the Township Engineer determines that off-site improvements are necessary to satisfactorily control the stormwater from the site, the applicant shall be responsible for such off-site improvements.
G. All stormwater detention and retention facilities shall be in place and functioning prior to the creation of any impervious surface.
H. Whenever a watercourse, stream or intermittent stream is located within a grading site, it shall remain open in its natural state and location and shall not be piped unless permitted by DEW and the Township Board of Commissioners. See Upper Dublin chapter 240 for activity in and near a watercourse,
I. The existing points of natural drainage discharge from and onto adjacent properties shall not be altered without the written approval of and a drainage easement from the affected upstream and downstream landowners.
J. No stormwater runoff or natural drainage shall be so diverted as to overload existing drainage systems or create flooding or the need for additional drainage structures on other private properties or public lands.