Drainage Report. For: Owner/Developer:

Transcription

1 Drainage Report For: My Place Hotel Lot 6, Charles Ritz Subdivision Overland Park, KS Owner/Developer: Overland Park Holdings, LLC Matt Eller 104 Campus Drive, Suite 202 Huxley, IA Civil Engineer: Legacy Design Group, LLC Craig B. Larsen, PE 576 West 900 South, Suite 105 Woods Cross, UT Preparation Date: December 2017 Revised: January I G B. LARSEN CRA L I CENS ED P ROF E S S K A N S A I ONA L S N E E R I E NG Jan. 29, 2018

2 Table of Contents Executive Summary... 1 SECTION G: Site Characteristics Existing Conditions Hot Spots Existing Soil Type & Curve Number (CN) Proposed Use & Curve Number (CN) Development Impacts and Level of Service (LS) Proposed Stormwater Treatment Drainage Areas Additional Treatment Credit Mitigation Package Calculations Proposed Stormwater Treatment Typical Bioretention Section Water Quality Control Volume Bioretention Cell Areas Maintenance and Easements to BMP s Preliminary Grading Plan Maintenance Responsibility... 7 References... 7 Appendix: Drawings... 7 Applicant Submittal i

3 Executive Summary A Final Stormwater Management Study has previously been submitted and approved that included the property of interest, Lot 6 of the Ritz Charles Plaza subdivision plat. The original report was prepared by Phelps Engineering for the Ritz Charles Plaza Subdivision. The study was dated October 9, The proposed development of Lot 6 is in substantial conformance with the original study with the exception of stormwater treatment. Stormwater treatment is now required and will be provided for the hotel lot. The open space amenity lot, located adjacent and Northeast of the hotel site, is not included in treatment calculations, with the exception of 1,197 sf to be improved as hotel parking, as it is fully considered under the original 2008 stormwater report and requirements. Section G of the Preliminary Stormwater Management Study as outlined in Overland Park Stormwater Management Studies will be addressed in this Stormwater Management Study with all other sections being addressed in the 2008 report. SECTION G: Site Characteristics 1. Existing Conditions The site primarily consists of vegetative cover, mostly grasses that are maintained by mowed. There are some areas of the site that have previously been developed. These areas include the existing alley access along the south property line, an existing drive aisle of the Candlewood Suites hotel along the southerly end of the east property line and parking and sidewalk along the west property line from Coaches Bar and Grill. The site naturally slopes southeasterly towards the existing alley access drive. The geotechnical investigation provided by PSI indicates: Based on information provided by the National Resources Conservation Service, the surficial soils overlying the bedrock described above have been classified as Woodson silt loam, which comprises silty loess and silt and clay alluvium. The surficial soils in the project area have generally been altered by urban development. The existing soils are considered to be Group D per the NRCS Hydrologic Soil Group Classifications. 2. Hot Spots Per Appendix B of the MARC BMP Manual the proposed development is not considered a hot spot. Applicant Submittal 3. Existing Soil Type & Curve Number (CN) Per the NRCS the existing site soils are considered to be in Hydrologic Soil Group D. The entire site is classified as Woodson Silt Loam. The existing condition of the site has a weighted CN of 77 (0 sf impervious CN 98; 62,622 sf weeds/grass-fair CN 77) for the purposes of this report. All existing (predevelopment) impervious area is not considered in these calculations as these improvements were installed prior to the stormwater treatement requirement. The weighted CN includes 1,197 sf of existing weeds/grass that is located outside of the My Place hotel lot but will be improved as parking for the My Place hotel. Runoff from this area will treated. 4. Proposed Use & Curve Number (CN) The proposed development consists of a four story hotel with associated parking and landscaping. It results in a weighted CN of 92 (42,923 sf impervious CN 98; 19,679 sf landscaping CN 80). The weighted CN includes 1,197 sf of existing weeds/grass that is located outside of the My Place hotel lot but will be improved as parking for the My Place hotel. 1

4 5. Development Impacts and Level of Service (LS) The site is part of a previously master planned area. At the time of master planning stormwater treatment was not required. With the increase in potential pollutants at the site due to development it is necessary to provide treatment to minimize impacts to water quality. A Level of Service of 7 is required with an increase of 15 from pre to post development CN per chapter 4 of the MARC BMP manual. Worksheet 1 of the manual is shown below with CN and LS calculations. t i m b u S t n a l ta p A c i l p 2

5 6. Proposed Stormwater Treatment It is proposed that stormwater treatment be provided by on-site bioretention cells. These cells will be located in two different areas which are the landscape island in the center of the parking lot and the area south of the building between the building and the private drive. These locations can be seen on the preliminary grading and drainage plan, C300, attached to this study. 7. Drainage Areas With the exception of a portion of the areas not being treated, the entire My Place hotel site drain to the existing stormdrain system near the southwest corner of the site. Specific drainage areas for the bioretention cells are shown in the figure below along with their associated bioretention cell locations and sizes. The maximum depth of the runoff to be treated within a cell is 1 foot. Applicant Submittal 3

6 LEGEND: NORTH BASIN TREATED AREA SOUTH BASIN TREATED AREA UNTREATED AREA EXISTING PRIVATE DRIVE pipe flow direction NORTH BIORETENTION CELL INFILTRATION AREA: 1,492 SF pipe flow direction OPEN SPACE AMENITY Applicant Submittal pipe flow direction 3 STORY - 64 GUEST UNITS pipe flow direction pipe flow direction SOUTH BIORETENTION CELL INFILTRATION AREA: 1,174 SF EXISTING PRIVATE DRIVE pipe flow direction

7 8. Additional Treatment Credit No additional treatment credit is being requested. 9. Mitigation Package Calculations. As mentioned earlier, mitigation and treatment will be provided by way of bioretention cells. Worksheet 2, providing calculations, is shown below. Each local drainage basin will be treated by one of the bioretention cells which will function independently. t i m b u S t n a l ta c i l p 10. p A Proposed Stormwater Treatment See paragraph 6 above. 11. Typical Bioretention Section. The MARC BMP Manuals typical section for the bioretention cells will be used and is shown below. 5

8 12. Water Quality Control Volume The Water Quality Control Volume, WQv, was determined using the shortcut method and is shown below. I = (62,622-19,679) / 62,622 = 69% WQv = 1.37 x ( x 69%) = 0.92 North basin WQV = 0.92 /12 x 30,011 = 2,301 cf South basin WQV = 0.92 /12 x 25,621 = 1,964 cf 13. Bioretention Cell Areas It is recommended that the maximum ponding depth of 12 be utilized for bioretention. For WQV s of 2,301 cf and 1,964 cf, minimum planting bed soil depth of 2.5 foot and a permeability coefficient of 1.5 ft/day the required filter bed surface area is 1,278 and 1,091 sf, respectively, per the MARC Bioretention worksheet below. The current site plan provides 1,492 and 1,174 sf, respectively, of filter bed surface area. 2,301 sf and 1,964 sf, respectively, of ponding area is required, if side slopes are not considered, and approximately 2,363 sf and 2,967 sf, respectively, of ponding area is provided. Applicant Submittal 6

9 14. Maintenance and Easements to BMP s Reasonable vehicular access will be provided to or near the bioretention cells to perform regular maintenance. Easements that may be required by the city will also be provided as necessary. 15. Preliminary Grading Plan A preliminary grading plan is attached here indicated existing and proposed grading patterns. 16. Maintenance Responsibility The property owner and operator, Columbia Hospitality, LLC, will be responsible for performing routine maintenance on the BMP s. References 1. Mid-America Regional Council, Manual of Best Management Practices for Stormwater Quality (October 2012) Appendix: 1. Drawings Applicant Submittal 7

10 PROJECT CONTACTS BUILDING/PARKING LOT NOTES OVERALL SITE & VICINITY MAP LEGACY DESIGN GROUP ABERDEEN, SD SALT LAKE CITY, UT LOT DEVELOPMENT NOTES WEST 135TH ST 2018 BY LEGACY DESIGN GROUP, LLC; DRAWING NOT TO BE REUSED IN WHOLE OR IN PART WITHOUT WRITTEN PERMISSION OWNER: OVERLAND PARK HOLDINGS, LLC OVERLAND PARK 8995± WEST 135TH ST. OVERLAND PARK, KS CENTRA CARE SLIM CHICKENS SCOOTERS RETAIL CENTER LEGAL DESC.: LOT 6, FINAL PLAT OF RITZ CHARLES PLAZA SITE DATA TABLE SHEET INDEX & REVISION TABLE LANDSCAPING NOTES GRAND VIEW OPEN SPACE AMENITY COACHES BAR & GRILL CANDLEWOOD SUITES 64 GUEST UNITS 3 STORIES Know what's below. Callbeforeyou dig. Rev. Date Comment - 5/22/18 2ND SUP APPLICATION DRAWN BY: CBL DESIGN BY: CBL ORIG. ISSUE DATE: 12/19/2017 CRA I G B. LARSEN L I CENSED BANQUET FACILITY PROF E S S K A N S A S I ONAL I NE E R ENG 0 SCALE ( FT ) /22/ :12:41 AM CIVIL COVER SHEET C000

11 OVERALL SITE LAYOUT LEGACY DESIGN GROUP ABERDEEN, SD SALT LAKE CITY, UT PRIVATE DRIVE 2018 BY LEGACY DESIGN GROUP, LLC; DRAWING NOT TO BE REUSED IN WHOLE OR IN PART WITHOUT WRITTEN PERMISSION OWNER: OVERLAND PARK HOLDINGS, LLC OVERLAND PARK 8995± WEST 135TH ST. OVERLAND PARK, KS LEGAL DESC.: LOT 6, FINAL PLAT OF RITZ CHARLES PLAZA OPEN SPACE AMENITY CANDLEWOOD SUITES COACHES BAR & GRILL 64 GUEST UNITS 3 STORIES Know what's below. Callbeforeyou dig. Rev. Date Comment - 5/22/18 2ND SUP APPLICATION DRAWN BY: CBL DESIGN BY: CBL ORIG. ISSUE DATE: 1/29/2018 CRA I G B. LARSEN L I CENSED PRIVATE DRIVE PROF E S S K A N S A S I ONAL I NE E R ENG BANQUET FACILITY 0 SCALE ( FT ) /22/ :11:32 AM OVERALL CIVIL SITE C002

12 LEGACY DESIGN GROUP ABERDEEN, SD SALT LAKE CITY, UT BY LEGACY DESIGN GROUP, LLC; DRAWING NOT TO BE REUSED IN WHOLE OR IN PART WITHOUT WRITTEN PERMISSION OWNER: OVERLAND PARK HOLDINGS, LLC OVERLAND PARK 8995± WEST 135TH ST. OVERLAND PARK, KS LEGAL DESC.: LOT 6, FINAL PLAT OF RITZ CHARLES PLAZA OPEN SPACE AMENITY COACHES BAR & GRILL BIORETENTION CELL CANDLEWOOD SUITES 64 GUEST UNITS 3 STORIES Know what's below. Callbeforeyou dig. Rev. Date Comment - 5/22/18 2ND SUP APPLICATION DRAWN BY: CBL DESIGN BY: CBL ORIG. ISSUE DATE: 12/19/2017 CRA I G B. LARSEN L I CENSED PROF E S S K A N S A S I ONAL I NE E R ENG 0 SCALE ( FT ) /22/ :10:41 AM SITE PLAN C100

13 LEGACY DESIGN GROUP ABERDEEN, SD SALT LAKE CITY, UT SLOPES TABLE 2018 BY LEGACY DESIGN GROUP, LLC; DRAWING NOT TO BE REUSED IN WHOLE OR IN PART WITHOUT WRITTEN PERMISSION OWNER: OVERLAND PARK HOLDINGS, LLC OVERLAND PARK 8995± WEST 135TH ST. OVERLAND PARK, KS LEGAL DESC.: LOT 6, FINAL PLAT OF RITZ CHARLES PLAZA COACHES BAR & GRILL BIORETENTION CELL FILTRATION AREA: 1,278 sf CANDLEWOOD SUITES Know what's below. Callbeforeyou dig. Rev. Date Comment - 5/22/18 2ND SUP APPLICATION DRAWN BY: CBL DESIGN BY: CBL ORIG. ISSUE DATE: 12/19/2017 BIORETENTION CELL FILTRATION AREA: 1,091 sf CRA I G L B. I CENSED LARSEN PROF E S S K A N S A S I ONAL I NE E R ENG 0 SCALE ( FT ) /22/ :09:42 AM GRADING PLAN C300