3301 SEAWAY BLVD WHOLE SITE 2025-10-30

PUBLIC WORKS not yet been met for the design of the stormwater control pond on this site. I have printed out the appropriate pages and highlighted the criteria that haven't been met. In my opinion, the City's general design criteria for flow control and treatment BMPs are the least stringent criteria that must be met to ensure the safety of the stormwater control facility at this location. All parts of the City's Stormwater Management Manual must be met to be in compliance with City Standards and for the City to be able to issue a permit. Please pay particular attention to the highlighted elements for specific criteria that need to be addressed on the plans in the resubmittal. 1. In particular, please carefully follow section 2.11 Setbacks of the 2010 Stormwater Management Manual. Item 1.c. lists that in no case shall the setback from the steep slope be less than the vertical height of the slope. This must be stringently followed. A generous look at the steep slope indicates that the vertical height of the steep slope is between 90 and 100'. This means that the setback from the top of the steep slope for any construction (retaining wall, stormwater facility, etc.) must be no less than 90-100' (whatever you determine with your engineering expertise and justification). The detention pond will likely need to be reconfigured to be located outside of this critical setback and may require vertical cuts instead of sloped walls in order to achieve this. ii. Please see the second attachment for the criteria in the Planned Action Determination (PAD) that haven't been met at this time. Of particular importance for this site is the construction management plan. I briefly reviewed the SWPPP that was included in the drainage report and it isn't adequate to address the conditions in the PAD, particularly with respect to implementing the recommendations in the geotechnical report and the provision of a construction sequencing plan. It also includes an incorrect description of the proposed construction activities in Section 2.2. On this site, the stormwater detention pond is proposed to serve as the project's sediment control pond. However, requirement #18 prohibits exfiltration from the pond during all phases of construction. How and when will the pond be built and, in particular, lined to prevent exfiltration from the pond? How much clearing will be allowed before this critical facility is constructed? Will the site be cleared and graded all at once? How will the slopes of the pond be protected during clearing and grading? These and additional questions must be answered and outlined on the plans for the contractor to follow. 1. The TESC Plan likely needs to have additional information or be revised to meet these criteria. It is highly advised that stormwater from the site during construction is collected in other methods such as a baker tank and not routed to the detention pond. Careful construction is required including an impermeable pond liner, so no construction runoff should be routed to it. /7c2 Page 2 of 4