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HomeMy WebLinkAboutComments PWE 9/6/2007 Memorandum Subject: September 6, 2007 Gary Karp, Planner III Matt Stouder, P.E., Civil Engineer ZON2007 -00030 Marcola Meadows Master Plan City of Springfield ~~@ceom~m W SEP 6 2001 W pu.) ~,e. c. By (.0 'l'V) 1'l'I..e.\.A.~ Date: To: From: Public Works Engineering has reviewed the above referenced application and provided the following comments for your use. SDC 37.030 Master Plan Submittal Requirements (9) Maps and narrative showing off-site publzc improvements necessary to serve the proposed development and lor to mitigate impacts to adjacent property or pubic facilities (10) The Director may require additional information necessary to evaluate the proposed development including but not limited to an ESEE analysis, geology, so,ils, stormwater, sanitary, tree preservation, historical, archaeological, and traffic impact All related maps except vicinity . and detail maps shall be at the same scale (J 2) An overall schedule or description of phasing, and the development to occur m each phase. If phasing is contemplated, these alternatives should be described (13) Where off-SIte or other mfrastructure Improvements are required, the applicant shall specify the tIming and method of securing the improvement, including bond, letter of credit, joint deposit or other security satisfactory for said improvement construction (J 4) Designation of Responsibility for providing infrastructure and services. COMMENTS Submitted materials do not meet the requirements of criteria as stated above. The follow information is needed: 1. The narrative addresses sub-phases associated with the proposed development (e.g. - AI, A2, A3, etc.). The plan set does not reflect this information, only showing 2 large phases (A & B). 2. The stormwater drainage report does not include any "off-site" flows in the analysis. As shown on the plan, the large drainage ditch will be relocated and enhanced. This ditch conveys water from a large drainage basin. Inclusion of this in water in the analysis is necessary because it will impact detention reservoir requirements, hydraulic grade lines, routing calculations, etc. ~~ -, 0 f? n ; } 1-= lJ iJ, IJ ,jJ SEP ll~m 6 200f lV By 3. The stormwater drainage report and/or mapping does not include hydraulic gra e me information or associated calculations. Hydraulic routing calculations were also not included with the report. This information is critical in the design of the stormwater system, as it will determine how the system will function during a storm event. Specifically, it will dictate how the onsite system will need to be designed (due to surface water elevation levels and any possible associated flooding). Additionally, the applicant will be required to look at surface water elevations (HGL elevations) and the impact these elevations may have on adjacent property owners (for instance the weir proposed 6 feet above the 10 inch outlet pipe may result in flooding of the subdivision to the north and west of the site). 4. The stormwater drainage report and/or mapping does not clearly indicate the locations of the proposed detention pond areas, or at least the sizes/volumes of each area and how they will function. Plan Amendment/Zone-Change Conditions of Approval Condition of Approval #11 Submittal of a Master Plan application that shows the entire length of the collector street from Marcola Road to V Street being constructed as part of Phase 1 COMMENTS 1. Submitted materials do not contain a proposal to address Condition # 11. It will be crucial for the applicant to detail out specific phasing on the plan set. In the planning for the entire length of the collector street, the applicant will be required to install the necessary utilities as shown on the plan set, and to plan for locations for utility crossings, stub outs, etc. The utilities associated with the collector street should be shown as part of work to be constructed with the appropriate phase. General Comments 2. The existing sanitary sewer line near the Pierce Parkway and 28th Street is shown to be located under newly proposed buildings. The buildings in this area will need to be revised such that the line nor easement is located under any proposed buildings. 3. The existing 42 inch sanitary sewer line is accurately shown to be located within an existing 20 foot sewer easement. Due to the depth of this line, additional easement is likely to be necessary for sufficient maintenance and access. 4. The location of the proposed water line, located in a proposed 15 foot easement, may require further attention. Placement of a water line in close proximity to the deep existing sanitary sewer line may not allow for sufficient maintenance access in the event the City were required to dig up and/or replace the existing 42 inch sewer line. 5. There appears to be opportunity at this site to direct stormwater runoff from rooftop areas to infiltration basins onsite to help eliminate some capacity issues which may exist downstream. Soil types onsite consist of 75 - Malabon and 118 - Salem soils. Both soils have relatively low clay contents. Salem soils have high infiltration rates (on the order of 20 inches per hour in some cases). 6. Additionally, with permeable soils onsite, there is opportunity for low impact development techniques to reduce the rates of stormwater runoff from the site. Consultation with the City and Springfield Utility Board's water division would be beneficial prior to designing these techniques. 7. Capacity is available in the 42 inch public sanitary sewer system located onsite for the proposed development. 8. Maintenance of the large swale green area will be of concern to the Public Works Department. The City will assume responsibility for the functionality of the area - it will be the responsibility of the property owners/developer to maintain the area aesthetically. 9. More information is needed for the drainage system with regards to the northern water quality pond. Specifically, the applicant should provide the amount of flow received by this pond, and provide a comparison and both pre and post developed flow rates. 10. Flow line information will be needed for the storm drainage system. ~[E@~OW~rml IW SEP 6 200' ~ By