City Council Worksession

South St. Paul MAYOR/COUNCIL WORKSESSION SSP City Hall 125 3rd Avenue North Training Room Monday, October 22, 2018 7:30 p.m. AGENDA: 1. Discussion: 11th Avenue South Alley Drainage 2. Budget: Fees & Charges 3. Update: John Carroll Sprinkler Head Replacement Project – No attachment 4. AE2S Communication Support Services Proposal 5. Update: Concord Street Proposal Selection – No attachment 6. Update: Southview Boulevard Consultant Scope Amendment – No attachment A COUNCIL WORKSESSION REPORT DATE: OCTOBER 22, 2018 1 DEPARTMENT: Engineering ADMINISTRATOR: ____________ AGENDA ITEM: 11th Avenue South Alley Drainage Discussion ACTION TO BE CONSIDERED: Information item only; for input & discussion OVERVIEW: On August 10, 2018, the City was made aware of an existing drainage issue on the 11th Avenue South alley in conjunction with the construction of the Southview Boulevard Improvements project. The issue was exacerbated by very heavy rainfalls on August 3rd and throughout the months of August, September, and early October (Attachment A – Letter from Resident). Staff immediately recognized the issue and promptly studied the corridor to figure out the root cause of the situation and feasible alternatives to address the problem. Staff reviewed the previous engineering analysis and subsequent inlet additions before considering other potential solutions (Attachment B – 2012 Engineering Letter). DRAINAGE ANALYSIS: Staff has completed a preliminary analysis of the drainage concerns. The drainage area generally extends from 4th Street to Southview Boulevard and from 15th Avenue to just east of 10th Avenue. Based on historical photos and staff knowledge, the commercial area north of 3rd Street was redeveloped from residential to commercial land use, which increased the impervious runoff. However, no ponding, infiltration devices, or storm sewer pipe upsizing were considered at that time. The storm sewer system in 3rd Street had adequate capacity through gravity and head pressure to convey the storm water from the contributing drainage area. However, there is a deficiency of storm sewer inlets and the alley surface inlet elevation is significantly lower than the roadway level in 3rd Street. The “tail-water” in the 3rd Street storm sewer system does not allow water to begin draining out of the alley until the upstream portions of the watershed are mostly drained out of the conveyance system (Attachment C – Flood Inundation Map). There are only two feasible and cost effective solutions to help ameliorate the flooding concerns on the 11th Avenue South alley. The first solution would be to construct a new storm sewer conveyance system with high capacity inlets at 3rd Street, which would eliminate a significant amount of flooding at a cost of approximately $530,000. The second solution would be similar to the first solution, with the exception that you would also need to construct a series of pipes and inlets on 12th Avenue and within the Southview Shopping Center property at a cost of approximately $750,000 (Attachment D – Alternative Solutions). City Council WS Report – 11th Avenue South Alley Drainage Discussion October 22, 2018 Page 2 of 2 RECOMMENDATIONS: Staff recommends that a new storm sewer conveyance system be considered when this project is considered for a future reconstruction project or if the Southview Shopping Center is being redeveloped. The project area was last milled and overlaid in 2008 and the pavement is in relatively moderate condition. Staff anticipates that a reconstruction project may occur in years 2030 to 2033. SOURCE OF FUNDS: No fiscal impact at this time. Attachment A: Letter from Resident  Attachment B: 2012 Engineering Letter w a ity ofSoutFi St. aul Engineering Department August 8, 2012 Drew and Meg Cavalier 308- 11th Avenue South South St. Paul, MN 55075 Dear Mr. and Mrs. Cavalier: My assistant and I have reviewed the drainage situation and have reviewed all of the old records and drawings for the drainage basins in the alley directly behind your home. Without doing a complete design analysis of your alley, I can observe and determined the following issues and facts: In 1974 the alley was paved in concrete and the catch basins existed in their current location prior to that 1974 paving In 1987, as part of a City wide sewer separation program, the catch basins were altered to their current design and configuration. The plans are not total clear on what was done other than they were modified I am not aware of any other work that has been since 1987 This ' triple' catch basin arrangement is one I have not seen before and was clearly installed to catch as much water as possible at this low point Your driveway is directly adjacent to the low point of the alley and your driveway has little, to no grade, up from the low point of the alley. The catch basin grates are in good condition but the supporting structures underneath 2 of them are deteriorating. These catch basins catch about 550 feet of alley drainage, as there is no other catch basins along this alley. Alley catch basin grates are designed to catch as much water as possible without causing an impediment to traffic. In other words, the grates have to have small enough openings not to cause problems for vehicles, bikes, pedestrians or small children. By making the grates in this manner, the grates can get plugged by debris and thus inhibit flow I am not sure if this is a pipe capacity problem, in other words, if the water can get to the underground pipe then it should properly flow out into the City storm water system I will have the maintenance department check to make sure there is no blockage in the 12" pipe that drains out to 3rd Street South from these catch basins Do you believe you have observed a pipe capacity problem or is the problem that the grates get pluggedup and the water can' t get into the pipe system? Your observations can be very helpful in coming up with a proper solution. 125 Third Avenue North • South St, Paul, MN 55075 • www. southstpaul. org • ( 651) 554- 3210 • Fax ( 651) 554- 321 1 Drew and Meg Cavalier August 8, 2012 Page 2 The City does have a smali program for rebuilding deteriorated alley drains and this could likely address the problem if it is only a grate or inlet If it is a pipe capacity problem, then the problem. section all the way out to 3rd Street South would have to be rebuilt. Please let me know what you have observed and I will let you know if the maintenance department has seen any blockages in the pipe. Sincerely, John achi City Engineer Attachment C – Flood Inundation Map  Attachment D – Alternative Solutions Alternative No. 1 (Pink & Red) $530K Alternative No. 2 (Pink & Red) $750K