2202 100TH ST SW 2023-02-07 - Laserfiche WebLink

Benyam Stephanos From: Cindy Cullen Sent: Thursday, June 18, 2020 4:22 PM To: Benyam Stephanos Cc: Erik Emerson; Sabrina Fandler Subject: RE: 2202 100th Street S.W.(PW2004-012) Attachments: STORMWATER STRUCTURAL LOADING DESIGN VEHICLES -Draft.pdf Hi Benyam, Here are our comments: 1. Per the City of Everett DCSS, flow control is required for 5,000 SF of new and replaced hard surface, whereas the 2019 Manual specifies 10,000 SF. (This is only a correction to language in your report.) 2. Provide additional information on Source Control BMPs to meet Minimum Requirement #3 as there is more emphasis on Source Control in the 2019 Manual. The Source Control BMPs should be discussed separately from Construction BMPs. 3. The Manual requires that the site conditions and infeasibility criteria be documented to deem a BMP infeasible. Include language on why BMP T5.10C: Perforated Stub -out Connections was not used. 4. Minimum Requirement #8 a. Explain the project components used to comply with the General Protection Requirements. b. List Source Control BMPs from Minimum Requirement #3 as part of the Protection from Pollutants requirements in MR #8. Explain how on -site stormwater management and runoff treatment BMPs meet the Protection from Pollutants requirements. 5. Include the Operation and Maintenance Manual as a separate document. Include the specific O&M requirements for the modular wetland. 6. Flow Control / Treatment Trade c. The flow control trade of Basin D for Basin B appears to be inadequate as Basin D has less total and impervious area. Please provide a POC analysis for all basins to show that the duration standard is being met. d. Basin D collects less impervious area than Basin B. Please address whether the Basin D for Basin B trade provides equivalent treatment. 7. Provide a printout of the diagrams used for the WWHM model as well as the graphs. 8. Verify the impervious area for Basin C in the Rational Method calculations. Based on Everett mapping and the Basin Map figure, there appears to be more than 4.2 acres of impervious surface in Basin C. 9. Some of the plan set rim elevations and invert elevations do not match the StormCAD inputs. Please revise. 10. Access lids larger than the standard manhole lids shall be hinged and shall be capable of being opened and held open by a single individual. Please include this in your plans, including the detention vault access grate. Also, note that all access lids shall be equipped with a pick hole capable of being opened with a standard grate hook or handles. [DCSS 4-4.2(3)] 11. Is an additional access point needed for Cell 1 in the detention vault? The Manual requires that access openings for detention vaults be positioned at a maximum of 50 feet from any location within the vault. 12. See the attached structural design vehicle loading for the detention vault. Our policy is to have the capability to bring City trucks onsite to vactor/jet the structure if the owner is not maintaining it. You will need to submit structural calculations, but this can be deferred to construction as a permit condition.