STORMWATER MASTER PLAN Prepared for CITY OF DES PLAINES 1420 MINER STREET DES PLAINES, IL 60016 July 2003 CBBEL Project No. 02-73
TABLE OF CONTENTS Page # LIST OF TABLES... v LIST OF EXHIBITS... vi LIST OF APPENDICES... vii EXECUTIVE SUMMARY... ES-1 ES-4 INTRODUCTION... 1 FLOODING PROBLEM INVENTORY AND ASSESSMENT... 1 PROBLEM AREA #1... 4 Location... 4 Flood Protection Questionnaire... 4 Existing Drainage Pattern... 6 Drainage Problem... 6 Drainage Problem Causes... 6 PROBLEM AREA #2... 7 Location... 7 Flood Protection Questionnaire... 7 Existing Drainage Pattern... 9 Drainage Problem... 10 Drainage Problem Causes... 10 PROBLEM AREA #3... 11 Location... 11 Flood Protection Questionnaire... 11 Existing Drainage Pattern... 12 Drainage Problem... 12 Drainage Problem Causes... 12 PROBLEM AREA #4... 14 Location... 14 Flood Protection Questionnaire... 14 Existing Drainage Pattern... 15 Drainage Problem... 15 Drainage Problem Causes... 15 PROBLEM AREA #5... 17 Location... 17 Flood Protection Questionnaire... 17 Existing Drainage Pattern... 19 Drainage Problem... 19 Drainage Problem Causes... 19 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan i
PROBLEM AREA #6... 20 Location... 20 Flood Protection Questionnaire... 20 Existing Drainage Pattern... 22 Drainage Problem... 22 Drainage Problem Causes... 22 PROBLEM AREA #7... 23 Location... 23 Flood Protection Questionnaire... 23 Existing Drainage Pattern... 25 Drainage Problem... 25 Drainage Problem Causes... 25 PROBLEM AREA #8... 26 Location... 26 Flood Protection Questionnaire... 26 Existing Drainage Pattern... 28 Drainage Problem... 28 Drainage Problem Causes... 28 PROBLEM AREA #9... 29 Location... 29 Flood Protection Questionnaire... 29 Existing Drainage Pattern... 31 Drainage Problem... 31 Drainage Problem Causes... 31 PROBLEM AREA #10... 32 Location... 32 Flood Protection Questionnaire... 32 Existing Drainage Pattern... 33 Drainage Problem... 33 Drainage Problem Causes... 33 PROBLEM AREA #11... 35 Location... 35 Flood Protection Questionnaire... 35 Existing Drainage Pattern... 37 Drainage Problem... 37 Drainage Problem Causes... 37 PROBLEM AREA #12... 38 Location... 38 Flood Protection Questionnaire... 40 Existing Drainage Pattern... 40 Drainage Problem... 40 Drainage Problem Causes... 40 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan ii
FLOOD MITIGATION PROJECT ANALYSIS... 41 STORM EVENTS SIMULATED... 41 Design Storm Event... 41 October 13, 2001 Storm Event... 41 HYDROLOGIC AND HYDRAULIC MODELING... 41 PROBLEM AREA #1... 43 Watershed Description... 43 Existing Condition Analysis... 44 Flood Mitigation Project Analysis... 44 Summary... 45 PROBLEM AREA #2... 47 Watershed Description... 47 Existing Condition Analysis... 48 Flood Mitigation Project Analysis... 48 Summary... 51 PROBLEM AREA #3... 52 Watershed Description... 52 Existing Condition Analysis... 52 Flood Mitigation Project Analysis... 53 Summary... 57 PROBLEM AREA #4... 58 Watershed Description... 58 Existing Condition Analysis... 58 Flood Mitigation Project Analysis... 59 Summary... 61 PROBLEM AREA #5... 64 Watershed Description... 64 Existing Condition Analysis... 64 Flood Mitigation Project Analysis... 65 Summary... 67 PROBLEM AREA #6... 68 Watershed Description... 68 Existing Condition Analysis... 68 Flood Mitigation Project Analysis... 69 Summary... 69 PROBLEM AREA #7... 71 Watershed Description... 71 Existing Condition Analysis... 71 Flood Mitigation Project Analysis... 71 Summary... 71 PROBLEM AREAS #8 & 9... 73 Watershed Description... 73 Existing Condition Analysis... 74 Flood Mitigation Project Analysis... 75 Summary... 78 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan iii
PROBLEM AREA #10... 80 Watershed Description... 80 Existing Condition Analysis... 80 Flood Mitigation Project Analysis... 81 Summary... 82 PROBLEM AREA #11... 84 Watershed Description... 84 Existing Condition Analysis... 84 Flood Mitigation Project Analysis... 85 Summary... 88 PROBLEM AREA #12... 89 Watershed Description... 89 Existing Condition Analysis... 89 Flood Mitigation Project Analysis... 90 Summary... 91 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan iv
LIST OF TABLES Page # 1. Flood Protection Questionnaire Summary... 2 2. October 13, 2001 Storm Event Complaint Telephone Calls... 2 3. Problem Area #1 Flood Protection Questionnaire Summary... 4 4. Problem Area #1 October 13, 2001 Storm Event Summary... 4 5. Problem Area #2 Flood Protection Questionnaire Summary... 7 6. Problem Area #2 October 13, 2001 Storm Event Summary... 7 7. Problem Area #3 Flood Protection Questionnaire Summary... 11 8. Problem Area #3 October 13, 2001 Storm Event Summary... 12 9. Problem Area #4 Flood Protection Questionnaire Summary... 14 10. Problem Area #4 October 13, 2001 Storm Event Summary... 15 11. Problem Area #5 Flood Protection Questionnaire Summary... 17 12. Problem Area #5 October 13, 2001 Storm Event Summary... 17 13. Problem Area #6 Flood Protection Questionnaire Summary... 20 14. Problem Area #6 October 13, 2001 Storm Event Summary... 20 15. Problem Area #7 Flood Protection Questionnaire Summary... 23 16. Problem Area #7 October 13, 2001 Storm Event Summary... 23 17. Problem Area #8 Flood Protection Questionnaire Summary... 26 18. Problem Area #8 October 13, 2001 Storm Event Summary... 26 19. Problem Area #9 Flood Protection Questionnaire Summary... 29 20. Problem Area #9 October 13, 2001 Storm Event Summary... 29 21. Problem Area #10 Flood Protection Questionnaire Summary... 32 22. Problem Area #10 October 13, 2001 Storm Event Summary... 33 23. Problem Area #11 Flood Protection Questionnaire Summary... 35 24. Problem Area #11 October 13, 2001 Storm Event Summary... 35 25. Problem Area #12 Flood Protection Questionnaire Summary... 38 26. Problem Area #12 October 13, 2001 Storm Event Summary... 38 27. Problem Areas #8 & #9 Summary of Alternatives... 73 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan v
LIST OF EXHIBITS Page # 1. Flood Protection Questionnaire Survey Results... 3 2. Flooding Assessment Problem Area 1... 5 3. Flooding Assessment Problem Area 2... 8 4. Flooding Assessment Problem Area 3... 13 5. Flooding Assessment Problem Area 4... 16 6. Flooding Assessment Problem Area 5... 18 7. Flooding Assessment Problem Area 6... 21 8. Flooding Assessment Problem Area 7... 24 9. Flooding Assessment Problem Area 8... 27 10. Flooding Assessment Problem Area 9... 30 11. Flooding Assessment Problem Area 10... 34 12. Flooding Assessment Problem Area 11... 36 13. Flooding Assessment Problem Area 12... 39 14. Recommended Projects For Problem Area 1... 46 15. Recommended Projects For Problem Area 2... 49 16. Recommended Projects For Problem Area 3... 53 17. (A) Recommended Projects For Problem Area 4 Alternative 1... 60 17. (B) Recommended Projects For Problem Area 4 Alternative 2... 61 18. Recommended Projects For Problem Area 5... 64 19. Recommended Projects For Problem Area 6... 68 20. Recommended Projects For Problem Area 7... 70 21. Recommended Projects For Problem Areas 8 & 9... 77 22. Recommended Projects For Problem Area 10... 81 23. Recommended Projects For Problem Area 11... 84 24. Recommended Projects For Problem Area 12... 90 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan vi
LIST OF APPENDICES (CD-ROM) 1. Hydrologic and Hydraulic Support Calculations and Opinions of Probable Cost Problem Area 1 Problem Area 2 Problem Area 3 Problem Area 4 Problem Area 5 Problem Area 6 Problem Area 7 Problem Area 8 & 9 Problem Area 10 Problem Area 11 Problem Area 12 2. Des Plaines SWMM Models Problem Area 2 Problem Area 3 Problem Area 4 Problem Area 5 Problem Area 7 Problem Area 8 & 9 Problem Area 12 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan vii
EXECUTIVE SUMMARY During the storm event that occurred on October 13, 2001, significant flooding occurred throughout the City of Des Plaines. Because of this storm event, the City of Des Plaines hired Christopher B. Burke Engineering, Ltd. (CBBEL) to prepare a Stormwater Master Plan for 12 problem areas identified by the City staff. The location of the 12 problem areas follows: Problem Area #1 Subdivision located south of Central Avenue, west of Wolf Road and north of Rand Road (Ward 7). Problem Area #2 Radcliffe Avenue between Wisconsin Drive on the north and Cranbrook Drive on the south (Ward 7). Problem Area #3 Subdivision located east of Mt. Prospect Road and north of Golf Road (Ward 7). Problem Area #4 Subdivision located west of Mt. Prospect Road, south of Golf Road and north of Thacker/Dempster Street (Ward 4). Problem Area #5 Leahy Circle East and Leahy Circle South (Ward 3). Problem Area #6 Third Avenue between Thacker/Dempster Street and Algonquin Road (Ward 3). Problem Area #7 Walnut Avenue west of Lee Street (Ward 2). Problem Area #8 Marshall Drive north of Oakton Street (Ward 8). Problem Area #9 Pennsylvania Avenue from Lancaster Lane to Oakton Street (Ward 8). Problem Area #10 Subdivision located north of Touhy Avenue, south of Jarvis Avenue, east of Wolf Road and west of Lake Opeka (Ward 5). Problem Area #11 Spruce Avenue south of Howard Street (Ward 5). Problem Area #12 Washington Street (Ward 1). The 1986 Stormwater Master Plan presented 24 recommended projects for a 20- year implementation plan. According to City Engineering staff, 17 of the recommended projects have been completed. The remaining projects, which include combined sewer separation and the installation of relief sewers will be completed during scheduled street rehabilitation work. The City of Des Plaines sent out a Flood Protection Questionnaire to all homeowners. During the October 13, 2001 storm event, the City of Des Plaines Public Works Department received telephone calls reporting basement flooding/sewer backup and street flooding. Tables ES-1 and ES-2 summarized the Flood Protection Questionnaire responses and the telephone calls received by the 12 problem areas, respectively. Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan ES-1 Executive Summary
The flooding problems were quantified and there causes determined using the information in Tables ES-1 and ES-2, discussions with City staff, site visits, review of available documents and hydrologic and hydraulic modeling. Table ES-1 Flood Protection Questionnaire Summary Number of Respondents Problem Area => #1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 Location of Flooding Basement Flooding 7 17 16 50 4 0 0 7 0 0 7 0 Crawl Space Flooding 0 1 1 14 0 0 0 2 1 0 6 0 First Floor Flooding 1 0 1 3 1 0 0 1 0 0 1 0 Yard Flooding 0 3 4 12 1 0 0 2 0 2 2 0 No Flooding 3 0 1 12 1 1 0 1 0 1 3 0 Cause of Flooding Storm Sewer Backup 5 15 9 44 3 0 0 5 1 0 5 0 Sanitary Sewer Backup 1 13 4 23 2 0 0 1 0 0 3 0 Sump Pump Failure/Power Failure 4 1 2 11 1 0 0 0 0 0 0 0 Basement Wall Seepage 1 4 4 25 2 0 0 2 0 0 5 0 Standing Water Next to House 1 3 1 11 0 0 0 2 0 0 3 0 Overbank Flooding 0 0 9 0 0 0 0 0 0 0 0 0 Table ES-2 October 13, 2001 Storm Event Summary Number of Respondents Problem Area => #1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 Flooding Type Basement Flooding/Sewer Backup 0 4 1 8 1 1 1 3 1 1 0 0 Street Flooding 0 2 5 22 1 7 6 2 1 0 3 0 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan ES-2 Executive Summary
Based on cause of the flooding problems, flood mitigation projects were developed and analyzed using the hydrologic and hydraulic models. The flood mitigation projects were designed to handle the greater of the 10-year critical duration storm event or the October 13, 2001 storm event. Table ES-3 summarizes for the 12 problem areas the Drainage Problem, Drainage Problem Cause, Flood Mitigation Project and Opinion of Probable Cost. The Opinion of Probable Cost includes a 30% contingency factor and includes an estimate for future engineering fees. Land acquisition costs have not been included in the Opinion of Probable Costs. The City of Des Plaines has an ongoing program to address reported rear yard flooding problems throughout the City. Using micro-tunneling techniques, new storm sewers are installed in the affected rear yards. Inlets are then installed to allow drainage into the new storm sewers. For the Citywide reported incidents of rear yard flooding, it is estimated the cost of the program would be $1,800,000. The reported rear yard flooding we completed on a yearly basis based on available funds. The returned Flood Protection Questionnaires indicate that 491 incidences of basement flooding were caused by combined and sanitary sewer backup. This type of flooding can be based addressed by the homeowner. Therefore it is recommended that homeowners be encouraged to install overhead sewers. This measure will significantly reduce the number of reported sewage backup in basements. The following priority list by problem area was developed based on a weighted ranking for reported structure first floor flooding, street flooding and yard flooding. The structure flooding was assigned a weight of 0.50, whereas the street flooding and yard flooding were assigned a weight of 0.25. Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan ES-3 Executive Summary
Problem Area Priority List Reported Incidences of Flooding Structure Street Yard Weighted Score Opinion of Probable Cost 4 3 22 33 15.25 $4,815,000- $6,585,000 3 1 5 5 3.00 $1,285,000- $1,655,000 11 1 3 5 2.50 $410,000- $486,000 8&9 1 3 4 2.25 $535,000 2 0 5 3 2.00 $1,065,000- $1,090,000 6 0 7 0 1.75 $205,000 7 0 6 0 1.50 $470,000 5 1 1 1 1.00 $340,000 1 1 0 1 0.75 $70,000- $275,000 10 0 0 2 0.50 $385,000- $1,435,000 12 0 0 0 0.00 $415,000 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan ES-4 Executive Summary
Table ES-3 Master Stormwater Plan Summary Problem Area Drainage Problem #1 Structure first floor, street, yard and basement flooding on Clayton Lane and Berkshire Lane. #2 Basement flooding from sanitary sewer and combined sewer backups, street flooding and rear yard flooding. Drainage Problem Cause Inadequate overland flow route over existing outlet sewer. The existing 21-inch storm sewer that drains the northern portion of Radcliffe Avenue and the combined sewer that drains the southern portion of Radcliffe Avenue do not have sufficient capacity to convey the runoff from the 10- year, 2-hour storm event. Flood Mitigation Project Installation of 24-inch relief sewer parallel to existing 27-inch outlet sewer and additional inlets at the southern end of Clayton Lane. Underground Storage (If required). For the northern portion of Radcliffe Avenue, a 12-inch to 15- inch relief storm sewer is proposed with additional inlets. In addition, 12-inch storm sewers are proposed to replace the existing 10-inch storm sewers that drain rear yards. Underground storage (If required). Design Storm Event 10-year, 2-hour 10-year, 2-hour Opinion of Probable Cost $70,000-$275,000 $255,000-$280,000 #3 Basement flooding from sanitary sewer backups caused by street flooding. Rear yards along Cumberland Parkway and Fletcher Drive are subject to overbank flooding from Weller Creek. Westgate Road and Cumberland Parkway/Warrington Road storm sewers do not have adequate capacity to convey the runoff from the 10-year, 1-hour. For the southern portion of Radcliffe Avenue, a 12-inch to 18- inch combined sewer is proposed. This new combined sewer would discharge to a new 24-inch to 27-inch combined sewer along Mt. Prospect Road that will discharge into to the MWRDGC TARP drop shaft near Weller Creek. Westgate Road area project involves the installation of a 12- inch storm sewer along Westgate Road north of Fletcher Drive and a 12-inch to 15-inch relief storm sewer parallel to existing Mt. Prospect Road storm sewer. Underground storage (If required). 10-year, 2-hour 10-year, 1-hour $810,000 $430,000-$450,000 #4 Basement flooding from sanitary sewer backup caused by street flooding. Yard flooding also reported throughout problem area. The existing storm sewer system does not have sufficient capacity to convey runoff from an October 13, 2001 storm event. An 18-inch 36-inch relief storm sewer is proposed to be installed parallel to the existing storm sewer along Warrington Road and Cumberland Parkway. A new outfall to Weller Creek would be installed. A 15-inch to 24-inch relief storm sewer is proposed along Meyer Ct., Warrington Rd., Davis Ct. and Cumberland Parkway. A new outfall is to Weller Creek is proposed. Underground storage (If required). Alternative 1 Relief storm sewers (15-inch to 72-inch) are proposed parallel to existing storm sewers with high capacity inlets. Stormwater Storage Basins (If required). 10-year, 1-hour October 13, 2001 $855,000- $1,205,000 $4,815,000- $6,585,000 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan ES-5 Executive Summary
Problem Area Drainage Problem #5 Basement, first floor, street and yard flooding #6 Street flooding on Third Avenue between Oakwood Avenue and Thacker Street. #7 Basement flooding and street flooding reported. #8 & #9 Street flooding on Marshall Drive causes water to spill down the driveways into the below ground level garages. Street flooding at Pennsylvania Avenue/Dover Drive. Drainage Problem Cause Existing combined sewer system does not have sufficient capacity to convey the October 13, 2001 storm event flows. No existing storm sewer. Existing storm sewer discharges to existing combined sewer. Marshall Drive storm sewer has insufficient capacity to convey the runoff from the October 13, 2001 storm event. Pennsylvania Avenue storm sewer does not have adequate capacity to convey the runoff October 13, 2001 storm event due to the surcharging of the Oakton Street storm sewer. #10 Street and yard flooding. There is no main sewer located along Jarvis Avenue that would serve the area to the south. Flood Mitigation Project Alternative 2 Similar to Alternative except two stormwater basins are proposed within the linear park adjacent to the ComEd Transmission lines. The use of stormwater storage will reduce the diameters of the proposed parallel relief storm sewers. Stormwater Storage Basins (If required). A 15-inch to 24-inch relief storm sewer is proposed to be installed along Leahy Circle South and Leahy Circle East that will discharge to the existing 36-inch storm sewer located along Leahy Circle East between Walnut Avenue and Thacker/Dempster Street. Additional high capacity inlets will be installed to reduce levels of street and yard flooding. The existing combined sewer will remain to handle the sanitary flow. A 21-inch storm sewer is proposed to be installed along Third Avenue from Oakwood Avenue to the existing Thacker Street storm sewer. Inlets will be installed as appropriate. A 15-inch to 30-inch storm discharging to existing 120-inch Oakwood Avenue storm sewer. A 30-inch relief storm sewer is proposed along Marshall Drive from Courtesy Lane southward to Wille Road where it will discharge to a new storm sewer being installed by a developer. The new relief storm sewer will outlet to the ditch located along the Northwest Tollway. This ditch discharges to Higgins Creek. Since the Marshall Drive runoff will be removed from the Oakton Street storm sewer system, the Pennsylvania Avenue storm sewer will be able drain better. Additional inlets will be installed along Marshall Drive and Pennsylvania Avenue. Installed a new main 18-inch to 27-inch storm sewer along Jarvis Avenue form Elmira Avenue to Lake Opeka. As the streets located south of Jarvis Avenue are reconstructed with a curb/gutter cross-section, the new street storm sewers can discharge to the proposed Jarvis Avenue main storm sewer. Underground storage (If required). Design Storm Event October 13, 2001 October 13, 2001 October 13, 2001 October 13, 2001 October 13, 2001 October 13, 2001 Opinion of Probable Cost $3,750,000- $5,075,000 $340,000 $205,000 $470,000 $535,000 $385,000- $1,435,000 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan ES-6 Executive Summary
Problem Area Drainage Problem Drainage Problem Cause Flood Mitigation Project Design Storm Event Opinion of Probable Cost #11 Basement, crawl space, first floor, yard and street flooding reported. No Spruce Street storm sewer is located south of Fargo Avenue and the existing Spruce Street combined sewer located between Fargo Avenue and Howard Street has inadequate capacity to convey the runoff from the 10- year, 1-hour. A 21-inch to 24-inch relief storm sewer is proposed along Fargo Avenue from Spruce Avenue to Lake Opeka. A 15- inch storm sewer will be installed along Spruce Street from a point 200 feet north of Fargo Avenue. This storm sewer will drain to the proposed Fargo Avenue relief storm sewer. A 12-inch to 15-inch storm sewer will be installed along the portion of Spruce Street located south of Fargo Avenue. This storm sewer will also drain to the proposed Fargo Avenue relief storm sewer. Inlets to the proposed storm sewer and relief storm sewer will be installed as required. Underground storage (If required). 10-year, 1-hour $240,000-$316,000 The combined sewer area of Spruce Avenue located between Fargo Avenue and Howard Street will be separated. A 12-inch to 21-inch storm sewer will be installed along Spruce Avenue and will discharge to the existing Howard Street storm sewer. 10-year, 1-hour $170,000 #12 Flooding of below level garages along Washington Street. Existing Washington Street storm sewer has inadequate capacity to convey the runoff from the 10-year, 1-hour storm event. A 24-inch relief storm sewer is proposed along Washington Street, Laurel Avenue and Perry Street outleting to the existing relief storm sewer located at Graceland Avenue. High capacity Inlets will be installed were needed. Reported Citywide yard flooding. No existing drainage system and blocked overland flow routes. Using microtunneling, new storm sewers with inlets installed. $1,800,000 TOTAL $10,730,000- $15,291,000 10-year, 1-hour $415,000 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan ES-7 Executive Summary
INTRODUCTION In 2001, the City of Des Plaines experienced three storm events that resulted in flooding in various areas of the City. The October 13, 2001 storm event, which produced approximately 3.8-inches of rainfall during a 3-4 hour period, produced significant flooding throughout the City. During the October 2001 event, the City s Public Works and Engineering Departments were very active in responding to telephone calls from distressed residents and implementing emergency measures to help reduce local flooding throughout the City. Because of the saturated soil conditions from small rains during the previous 72-hours, the runoff entering most storm sewers was greater than expected and exceeded the sewer s capacity and resulted in surcharging, manhole lids popping, numerous street and backyard flooding. The 1986 Stormwater Master Plan presented 24 recommended projects with a 20-year implementation plan. The City of Des Plaines has completed 17 of the recommended projects. The remaining projects, which include combined sewer separation and the installation of relief storm sewers will be completed during scheduled street rehabilitation work. Because of this storm and previous historical flooding in the City, the City has decided to update the 1986 plan to identify new problem areas, revisit the projects recommended in the 1986 plan, assess the cause of any new problems, and recommend possible solutions. As a result of their efforts and observations during that evening, the city identified and targeted 12 areas that this new study should focus on. On March 8, 2002, the City hired Christopher B. Burke Engineering, Ltd. (CBBEL) to update the 1986 Stormwater Master Plan by studying 12 City identified problem areas. This report documents for each problem area the location, Flood Protection Questionnaire results, existing drainage patterns, drainage problems, cause(s) of the drainage problems and the development of mitigation measures. The mitigation measures were designed to handle the October 13, 2001 storm event rainfall, which for most of the problem areas is greater than the 10-year, critical duration design storm event. During the August 22, 2002 storm event CBBEL visited the problem areas to document any observed street flooding. The O Hare International Airport precipitation gage recorded 4.5-inches of rain over a nine hour period during this storm event. A majority of the rainfall occurred during a 6-hour period. FLOODING PROBLEM INVENTORY AND ASSESSMENT The City of Des Plaines sent out a Flood Protection Questionnaire to all homeowners. The Flood Protection Questionnaire, which is attached, requested information from the homeowner including the years flooding occurred, where the water was and the depth, what caused the flooding and what type of flood protection measures have been installed. The City received 697 completed Flood Protection Questionnaires. Table 1 summarizes the returned Flood Protection Questionnaire Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 1
results. Table 1 Flood Protection Questionnaire Summary Location of Flooding Number of Respondents Basement Flooding 452 Crawl Space Flooding 107 First Floor Flooding 29 Yard Flooding 120 No Flooding 155 Cause of Flooding Storm Sewer Backup 311 Sanitary Sewer Backup 180 Sump Pump Failure/Power Failure 86 Basement Wall Seepage 180 Standing Water Next to House 98 Overbank Flooding 73 Exhibit 1 shows the general location of the flood protection questionnaire reported flooding problems. Table 2 summarizes the basement flooding/sewer backup and street-flooding telephone calls the City of Des Plaines Public Works Department received during the October 13, 2001 storm event. Table 2 October 13, 2001 Storm Event Complaint Telephone Calls Flooding Type Number of Respondents Basement Flooding/Sewer Backup 87 Street Flooding 146 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 2
EXHIBIT 1 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 3
PROBLEM AREA #1 Location Problem Area #1 is located south of Central Road, west of Wolf Road and north of Rand Road. Flood Protection Questionnaire The results of the returned Flood Protection Questionnaires are summarized in Table 3. Exhibit 2 shows the location of the reported drainage problems within Problem Area #1. Table 3 Problem Area #1 Flood Protection Questionnaire Summary Location of Flooding Number of Respondents Basement Flooding 7 Crawl Space Flooding 0 First Floor Flooding 1 Yard Flooding 0 No Flooding 3 Cause of Flooding Storm Sewer Backup 5 Sanitary Sewer Backup 1 Sump Pump Failure/Power Failure 4 Basement Wall Seepage 1 Standing Water Next to House 1 Overbank Flooding 0 Table 4 summarizes basement flooding/sewer backup and street flooding telephone calls that the City of Des Plaines Public Works Department received during the October 13, 2001 storm event for Problem Area #1. Table 4 Problem Area #1 October 13, 2001 Storm Event Summary Flooding Type Number of Respondents Basement Flooding/Sewer Backup 0 Street Flooding 0 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 4
EXHIBIT 2 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 5
Existing Drainage Pattern The surface runoff from Nelson Lane, Jon Lane, Patricia Lane and Berkshire Lane is conveyed westward to Clayton Lane via storm sewers and overland flow. At the southern end of Clayton Lane, two catchbasins collect the overland flow. A 27-inch storm sewer conveys the collected flow westward and then southward to a 54-inch storm sewer located along Rand Road. A portion of the Tracy Terrace surface runoff that is collected by two catchbasins is conveyed by 12-inch storm sewer northward into an underground detention storage facility located in the rear yard of 400 & 404 Tracy Terrace. The 1977 engineering plans for the Windy Point subdivision prepared by Fletcher Engineering Co., indicate a restrictor was placed at the outlet of the underground detention storage facility. The outflow from the underground detention storage facility also enters the 27-inch storm sewer located at the southern end of Clayton Lane. Drainage Problem Surface runoff collects in Clayton Lane at its southern dead end resulting in street inundation northward to Berkshire Lane. South of the Clayton Lane is Sioux Park. The returned Flood Protection Questionnaires reported basement flooding for homes along Clayton Lane and Berkshire Lane caused by storm sewer backup and sump pump/ power failure. Drainage Problem Causes The results of the returned Flood Protection Questionnaires, a field reconnaissance of the problem area and hydrologic and hydraulic calculations were used to determine the cause of the drainage problem. The southern end of Clayton Lane is a bowl were surface runoff can collect because there is an inadequate overland flow route. Once the catchbasins and or the storm sewer reach capacity, surface runoff will pond in this bowl resulting in street flooding that causes sewer backup into basements. Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 6
PROBLEM AREA #2 Location Radcliffe Avenue between Wisconsin Drive on the north and Cranbrook Drive on the south. Flood Protection Questionnaire The results of the returned Flood Protection Questionnaires are summarized in Table 5. Exhibit 3 shows the location of the reported drainage problems within Problem Area #2. Table 5 Problem Area #2 Flood Protection Questionnaire Summary Location of Flooding Number of Respondents Basement Flooding 17 Crawl Space Flooding 1 First Floor Flooding 0 Yard Flooding 3 No Flooding 0 Cause of Flooding Storm Sewer Backup 15 Sanitary Sewer Backup 13 Sump Pump/Power Failure 1 Basement Wall Seepage 4 Standing Water Next to House 3 Overbank Flooding 0 Table 6 summarizes basement flooding/sewer backup and street flooding telephone calls that the City of Des Plaines Public Works Department received during the October 13, 2001 storm event for Problem Area #2. Table 6 Problem Area #2 October 13, 2001 Storm Event Summary Flooding Type Number of Respondents Basement Flooding/Sewer Backup 4 Street Flooding 2 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 7
EXHIBIT 3 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 8
Existing Drainage Pattern A portion of Radcliffe Avenue drains north and another portion drains south. For the area draining north, Radcliffe Avenue drains northward from a point north of Princeton Street to Wisconsin Drive. Midway between Princeton Street and Harvard Street there are two catchbasins on the west and east sides of Radcliffe Avenue. These catchbasins collect the tributary surface runoff into a 12-inch storm sewer. Another 12-inch storm sewer from the west conveys rear yard flows to this point. The Radcliffe Avenue 12-inch storm sewer drains northward changing to a 21-inch storm sewer at Harvard Street. At the Radcliffe Avenue/Harvard Street intersection, four catchbasins collect surface runoff into the storm sewer. Two catchbasins are located at the Radcliffe Avenue/Wisconsin Drive intersection. The City s Sanitary and Storm Sewer Map shows additional 12-inch storm sewers that convey rear yard surface runoff from the homes located on the west side of Radcliffe Avenue between Harvard Street and Wisconsin Drive. The Radcliffe Avenue 21-inch storm sewer discharges to the west to east flowing 24-inch storm sewer on Wisconsin Drive. This storm sewer eventually discharges to the 54-inch Rand Road storm sewer. For the area draining south, Radcliffe Avenue drains southward from a point north of Princeton Street to Cranbrook Drive through an 18-inch combined sewer according to the City s Sanitary and Storm Sewer Map. A 21-inch combined sewer along Cranbrook Drive conveys the collected flow westward to a 27-inch combined sewer flowing north to south located along Mt. Prospect Road. A portion of Princeton Street flows into the Radcliffe Avenue combined sewer. A catchbasin is located at the southeast corner of the Princeton Street/Radcliffe Avenue intersection. Two catchbasins are north of Cranbrook Street on the east and west sides of Radcliffe Avenue. A catchbasin is also located at the northeast corner of the Cranbrook Street/Radcliffe Avenue intersection. These four catchbasins are the only way that Radcliffe Avenue surface runoff can enter the combined sewer system. Drainage Problem The properties on the eastern side of Radcliffe Avenue between Harvard Street and Wisconsin Drive report basement flooding from storm sewer and sanitary sewer backup. Yard flooding was also reported on the west side of Radcliffe Avenue from Princeton Street northward past Harvard Street. Basement flooding caused by the surcharging of the combined sewer was reported for homes along Radcliffe Avenue between Cranbrook Street and Princeton Street. Basement flooding was also reported along the eastside of Mt. Prospect Road. During the October 13, 2001 storm event, basement backup and street flooding was reported along Radcliffe Avenue and Mt. Prospect Road. Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 9
Drainage Problem Causes The results of the returned Flood Protection Questionnaires, a field reconnaissance of the problem area and hydrologic and hydraulic modeling were used to determine the cause of the drainage problem. The 21-inch storm sewer along the northern portion of Radcliffe Avenue does not have sufficient capacity to convey the tributary flow generated by 10-year, 2-hour storm event. This results in street inundation at the location of the catchbasins causing the basement flooding of adjacent homes. The combined sewer system that serves the southern portion of the Radcliffe Avenue also does not have sufficient capacity to convey the tributary runoff generated by a 10-year, 2-hour storm event. Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 10
PROBLEM AREA #3 Location The problem area is located east of Mt. Prospect Road, south of Northwest Highway and north of Golf Road. Streets within this subdivision include Warrington Road, Meyer Court, Davis Court, Cumberland Parkway, Fletcher Drive and Westgate Road. Flood Protection Questionnaire The results of the returned Flood Protection Questionnaires are summarized in Table 7. Exhibit 4 shows the location of the reported drainage problems within Problem Area #3. Table 7 Problem Area #3 Flood Protection Questionnaire Summary Location of Flooding Number of Respondents Basement Flooding 16 Crawl Space Flooding 1 First Floor Flooding 1 Yard Flooding 4 No Flooding 1 Cause of Flooding Storm Sewer Backup 9 Sanitary Sewer Backup 4 Sump Pump/Power Failure 2 Basement Wall Seepage 4 Standing Water Next to House 1 Overbank Flooding 9 Table 8 summarizes basement flooding/sewer backup and street flooding telephone calls that the City of Des Plaines Public Works Department received during the October 13, 2001 storm event for Problem Area #3. Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 11
Table 8 Problem Area #3 October 13, 2001 Storm Event Summary Flooding Type Number of Respondents Basement Flooding/Sewer Backup 1 Street Flooding 5 Existing Drainage Pattern This subdivision drains to Weller Creek, which is a tributary of the Des Plaines River, through two outfalls according to the City s Sanitary and Storm Sewer Map. Westgate Road drains north to south towards Weller Creek. The street is served by a 12-inch to 15-inch storm sewer, which discharges to an 18-inch storm sewer flowing east to west located along Fletcher Drive. The 18-inch storm sewer connects to a 30-inch storm sewer flowing south near Mt. Prospect Road. This storm sewer outfall is to Weller Creek. Warrington Road, Meyers Court, Davis Court and Cumberland Parkway drain by storm sewers and overland flow to the Cumberland Parkway/Davis Court intersection. The storm sewers vary in diameter from 10-inch to 15-inch. The surface runoff collected at the Cumberland Parkway/Davis Court intersection is discharged to Weller Creek through a 24-inch storm sewer according to the City s Sanitary and Storm Sewer Map. Drainage Problem The drainage problems reported within this problem area include overbank flooding associated with Weller Creek and basement flooding caused by storm sewer and sanitary sewer backup. During the August 22, 2002 storm event a portion of Warrington Road was inundated between Cumberland Parkway and Davis Court. During the October 13, 2001 storm event, street flooding was reported on Warrington Road, Westgate Road, and Cumberland Parkway. Drainage Problem Causes The results of the returned Flood Protection Questionnaire, a field reconnaissance of the problem area and hydrologic and hydraulic modeling were used to determine the cause of the drainage problem. The upper portion of the Cumberland Parkway storm sewer system does not have adequate capacity to convey the runoff from the 10-year, 1-hour storm event. The Westgate Road storm sewer system also has inadequate capacity to convey the 10-year, 1-hour storm event. The rear yards of homes along Cumberland Parkway and Fletcher Drive are subject to overbank flooding from Weller Creek. Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 12
EXHIBIT 4 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 13
PROBLEM AREA #4 Location The problem area is located east of Elmhurst Road, west of Mt. Prospect Road, south of Golf Road and north of Dempster Street. Streets within this subdivision include Ambleside Drive, Bennett Lane, Beau Drive, Bell Drive, Bradley Street, Brentwood Drive, Cavan Lane, Dara James Road, Debra Drive, Dulles Road, Easy Street, Kathleen Drive, Lance Drive, Lawn Lane, Leahy Circle East, Marshall Street, Millers Road, Norman Court, Sandy Lane, Westmere Road, and Wilkins Drive. Flood Protection Questionnaire The results of the returned Flood Protection Questionnaires are summarized in Table 9. Exhibit 5 shows the location of the reported drainage problems within Problem Area #4. Table 9 Problem Area #4 Flood Protection Questionnaire Summary Location of Flooding Number of Respondents Basement Flooding 50 Crawl Space Flooding 14 First Floor Flooding 3 Yard Flooding 12 No Flooding 12 Cause of Flooding Storm Sewer Backup 44 Sanitary Sewer Backup 23 Sump Pump/Power Failure 11 Basement Wall Seepage 25 Standing Water Next to House 11 Overbank Flooding 0 Table 10 summarizes basement flooding/sewer backup and street flooding telephone calls that the City of Des Plaines Public Works Department received during the October 13, 2001 storm event for Problem Area #4. Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 14
Table 10 Problem Area #4 October 13, 2001 Storm Event Summary Flooding Type Number of Respondents Basement Flooding/Sewer Backup 8 Street Flooding 22 Existing Drainage Pattern The main storm sewer for this subdivision is located along Millers Road and flows west to east. The Millers Road storm sewer diameter varies from 12- to 48-inch when it reaches Mt. Prospect Road. The flow is then conveyed northward in the 48- inch Mt. Prospect storm sewer until it turns eastward in a 60-inch storm sewer, which discharges to Weller Creek. Located on Beau Drive, Marshall Street, Dara James Road and Leahy Circle are submain storm sewers with diameters of 36-inch, 34- inch, 21-inch and 24-inch, respectively that discharge to the Millers Road main storm sewer from the north and from the south. Drainage Problem Basement flooding caused by storm sewer and sanitary sewer backup have been reported throughout the problem area. During the October 13, 2001 storm event street flooding was reported on many of the streets within the subdivision (Ambelside Road, Bradley Street, Beau Drive, Debra Drive, Easy Street, Kathleen Drive, Lance Drive, Leahy Circle East, Marshall Drive, Millers Road, Sandy Lane, and Westmere Road resulting in basement and yard flooding to various degrees. Drainage Problem Causes The results of the returned Flood Protection Questionnaires, a field reconnaissance of the problem area and hydrologic and hydraulic modeling were used to determine the cause of the drainage problem. The hydrologic and hydraulic modeling indicates that over 420 acres are drained by the Millers Road storm sewer system. The submains and main storm sewer system has conveyance capacity less than the surface runoff from the October 13, 2001 historic storm event. The storm sewer diameters that drain to the various submain storm sewers range from 12-inch to 36- inch. In addition to the limited capacity of the Millers Road storm system (conveyance capacity is inadequate to handle the runoff from the October 13, 2001 historic storm event), there are a limited number of catchbasins that allow the surface runoff to enter the storm sewer system. A typical catchbasin has limited inflow capacity that can be severely impacted by debris blockage (i.e. leafs, etc.). Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 15
EXHIBIT 5 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 16
PROBLEM AREA #5 Location The problem area is Leahy Circle East and Leahy Circle South located south of Thacker Street and west of Mt. Prospect Road. Flood Protection Questionnaire The results of the returned Flood Protection Questionnaires are summarized in Table 11. Exhibit 6 shows the location of the reported drainage problems within Problem Area #5. Table 11 Problem Area #5 Flood Protection Questionnaire Summary Location of Flooding Number of Respondents Basement Flooding 4 Crawl Space Flooding 0 First Floor Flooding 1 Yard Flooding 1 No Flooding 1 Cause of Flooding Storm Sewer Backup 3 Sanitary Sewer Backup 2 Sump Pump/Power Failure 1 Basement Wall Seepage 2 Standing Water Next to House 0 Overbank Flooding 0 Table 12 summarizes basement flooding/sewer backup and street flooding telephone calls that the City of Des Plaines Public Works Department received during the October 13, 2001 storm event for Problem Area #5. Table 12 Problem Area #5 October 13, 2001 Storm Event Summary Flooding Type Number of Respondents Basement Flooding/Sewer Backup 1 Street Flooding 1 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 17
EXHIBIT 6 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 18
Existing Drainage Pattern The City s Sanitary and Storm Sewer Map indicates that a 36-inch storm sewer that connects to a storm sewer along Thacker Street drains Leahy Circle East between Walnut Avenue and Thacker Street. Leahy Circle East south of Walnut Avenue is served by an 8-inch to a 36-inch combined sewer that connects to a 42-inch combined sewer located along Thacker Street. The 42-inch combined sewer flows northward on Mt. Prospect Road to the MWRDGC Interceptor Sewer located on the north side of Weller Creek. Leahy Circle South is drained by an 8-inch combined sewer to a 15-inch combined sewer located on Stark Place, which connects to an 18-inch combined sewer located on Anderson Terrace, and then connects to a 30- inch combined sewer on Kincaid Court, which drains to the 33-inch combined sewer located on Leahy Circle East. Drainage Problem The returned Flood Protection Questionnaires indicate basement, first floor and yard flooding caused by combined sewer backup. During the August 22, 2002 storm event, Leahy Circle South was inundated west of Stark Place. Drainage Problem Cause The results of the returned Flood Protection Questionnaires, a field reconnaissance of the problem area and hydrologic and hydraulic modeling indicates that the Leahy Circle East combined sewer system conveyance capacity is less than the surface runoff from the October 13, 2001 historic storm event. There are a limited number of catchbasins that allow the surface runoff to enter the combined sewer system. A typical catchbasin has limited inflow capacity that can be severely impacted by debris blockage (i.e. leafs, etc.). Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 19
PROBLEM AREA #6 Location The problem area is located on Third Avenue between Thacker Street and Algonquin Road. Flood Protection Questionnaire The results of the returned Flood Protection Questionnaires are summarized in Table 13. Exhibit 7 shows the location of the reported drainage problems within Problem Area #6. Table 13 Problem Area #6 Flood Protection Questionnaire Summary Location of Flooding Number of Respondents Basement Flooding 0 Crawl Space Flooding 0 First Floor Flooding 0 Yard Flooding 0 No Flooding 1 Cause of Flooding Storm Sewer Backup 0 Sanitary Sewer Backup 0 Sump Pump/Power Failure 0 Basement Wall Seepage 0 Standing Water Next to House 0 Overbank Flooding 0 Table 14 summarizes basement flooding/sewer backup and street flooding telephone calls that the City of Des Plaines Public Works Department received during the October 13, 2001 storm event for Problem Area #6. Table 14 Problem Area #6 October 13, 2001 Storm Event Summary Flooding Type Number of Respondents Basement Flooding/Sewer Backup 1 Street Flooding 7 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 20
EXHIBIT 7 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 21
Existing Drainage Pattern Third Avenue from Algonquin Road to a point south of Oakwood Avenue drains to a storm sewer system that varies in diameter from 10-inch to 15-inch. The Third Avenue storm sewer conveys flows to the Walnut Street 18-inch to 24-inch storm sewer flowing west to east eventually discharging to a 24-inch combined sewer at Lee Street according to the City s Sanitary and Storm Sewer Map. The northern portion of Third Avenue from a point south of Oakwood Avenue to Thacker Street drains via a combined sewer 12-inch combined sewer whose flow eventually discharges to the MWRDGC Interceptor Sewer located along River Road. Drainage Problems No responses from the Flood Protection Questionnaire reported flooding along Third Avenue. During the October 13, 2001 storm event, The City of Des Plaines Public Works Department received one report of basement flooding and street flooding. During the August 22, storm event, Third Avenue between Thacker Street and Oakwood Avenue was flooded. During this storm event the Third Avenue storm sewer that connects to the Walnut Street storm sewer was conveying the tributary runoff with minor ponding above the catchbasins. Drainage Problem Causes Because the northern portion of Third Avenue has no storm sewer system, street flooding results. The Third Avenue storm sewer system near the Third Avenue/Walnut Avenue intersection has high capacity inlets installed that can handle the tributary surface runoff. Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 22
PROBLEM AREA #7 Location The problem area is located on Walnut Avenue west of Lee Street. Flood Protection Questionnaire The results of the returned Flood Protection Questionnaires are summarized in Table 15. Exhibit 7 shows the location of the reported drainage problems within Problem Area #7. Table 15 Problem Area #7 Flood Protection Questionnaire Summary Location of Flooding Number of Respondents Basement Flooding 0 Crawl Space Flooding 0 First Floor Flooding 0 Yard Flooding 0 No Flooding 0 Cause of Flooding Storm Sewer Backup 0 Sanitary Sewer Backup 0 Sump Pump/Power Failure 0 Basement Wall Seepage 0 Standing Water Next to House 0 Overbank Flooding 0 Table 16 summarizes basement flooding/sewer backup and street flooding telephone calls that the City of Des Plaines Public Works Department received during the October 13, 2001 storm event for Problem Area #7. Table 16 Problem Area #7 October 13, 2001 Storm Event Summary Flooding Type Number of Respondents Basement Flooding/Sewer Backup 1 Street Flooding 6 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 23
EXHIBIT 8 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 24
Existing Drainage Pattern A 24-inch storm sewer flowing west to east along Walnut Avenue discharges to a 24-inch combined sewer at Lee/Mannheim Road Street. An 18-inch combined sewer flowing west to east discharges to the 24-inch combined sewer at Lee/Mannheim Road Street. Drainage Problem During the October 13, 2001 storm event, basement flooding from sewer backup was reported at two locations on Walnut Avenue between Jeanette Street an Lee/Mannheim Road. Drainage Problem Causes The receiving 24-inch combined sewer does not have sufficient capacity to handle the Walnut Avenue storm sewer flow causing the reported surcharging. Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 25
PROBLEM AREA #8 Location The problem area is located on Marshall Drive north of Oakton Street. Flood Protection Questionnaire The results of the returned Flood Protection Questionnaire are summarized in Table 17. Exhibit 9 shows the location of the reported drainage problems within Problem Area #8. Table 17 Problem Area #8 Flood Protection Questionnaire Summary Location of Flooding Number of Respondents Basement Flooding 7 Crawl Space Flooding 2 First Floor Flooding 1 Yard Flooding 2 No Flooding 1 Cause of Flooding Storm Sewer Backup 5 Sanitary Sewer Backup 1 Sump Pump/Power Failure 0 Basement Wall Seepage 2 Standing Water Next to House 2 Overbank Flooding 0 Table 18 summarizes basement flooding/sewer backup and street flooding telephone calls that the City of Des Plaines Public Works Department received during the October 13, 2001 storm event for Problem Area #8. Table 18 Problem Area #8 October 13, 2001 Storm Event Summary Flooding Type Number of Respondents Basement Flooding/Sewer Backup 3 Street Flooding 2 Christopher B. Burke Engineering, Ltd. City of Des Plaines Stormwater Master Plan 26