Engineering Staff Report PHASE II REFERRAL

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3 Engineering Staff Report PHASE II REFERRAL Date: July 18, 2016 To: From: RE: Molly Orkild-Larson, Planning Division Sue Liu, Engineering Division P P Sky Ranch SDP FP Scope/Location: The applicant, Pure Cycle Corporation, is requesting approval of a Final Plat and a Specific Development Plan which addresses the Neighborhood B Portion of the overall Sky Ranch Developments. Neighborhood B is anticipated to be the first phase of development, including 506 single-family units. Two collector access points are planned off of Monaghan Road; one collector access point is planned off of East 6th Avenue. Interior roadways are planned adhering to the local 50 foot right-of-way cross-section. The site is located within the First Creek Drainage Basin. A floodplain delineation study for the First Creek Tributary (T-9) that crosses the Development Neighborhood B is required and will need to be approved by both Arapahoe County and Urban Drainage Flood Control District. In this study, the 100-year floodplain limits for the T-9 tributary will be defined, and regional detention facilities are also proposed within this application. Items included with this referral: Specific Development Plan Final Plat Phase II Drainage Study Traffic Impact Study Cc: Charles V. Haskins, Engineering Services Division, Division Manager Case File No. P P

4 Findings: The Arapahoe County Division of Engineering Services has reviewed this referral and has the following findings: 1. The Sky Ranch Development is partially within the Aurora Airpark Civilian Airport influence area. 2. The site lies within the First Creek basin and its tributary. 3. This development will require a Subdivision Improvement Agreement (SIA) to guarantee onsite and off-site public improvements for each proposed final site development plan (ASP). 4. Construction activities that disturb one or more acres are required by the Environment Protection Agency (EPA) to obtain a Construction Stormwater Permit. 5. This site lies within the Southeast Metro Stormwater Authority (SEMSWA) service area. This land use application will be referred to SEMSWA for review and comment. SEMSWA jointly reviews and approves the Phase II Drainage Study for all stormwater facilities. Their comments and concerns must be addressed prior to final County approvals. 6. This project is in the boundaries of the Urban Drainage and Flood Control District (UDFCD). The applicant is required to address UDFCD concerns related to this proposal as a condition of Arapahoe County engineering staff recommendation. 7. The applicant is required to provide a Floodplain Delineation Study for the First Creek tributary, T-9 that is across the Neighborhood B development. 8. A Floodplain Development Permit (FDP) will be required for all activities within a County designated floodplain, regardless of impact. 9. The applicant shall be permitted to design and construct 774 residential dwelling units of the Sky Ranch Development as detailed in the approved Traffic Impact Study for Sky Ranch Neighborhood B without filing a 1601 process with the Colorado Department of Transportation (CDOT). No further development beyond the 774 units will be permitted until the completion of the CDOT 1601 process for the Airpark Road and I-70 Interchange improvements. Recommendations: The Division of Engineering Services recommends this case favorably subject to the following conditions: 1. The applicant agrees to address the Division of Engineering Services findings, comments, and concerns as identified within this report. 2. The applicant agrees to address SEMSWA s comments and concerns. 3. The applicant agrees to address UDFCD s comments and concerns. 4. The applicant agrees to address CDOT s comments and concerns as identified within its report

5 STAFF COMMENTS General 1. In addition to the comments listed in this report, Staff has provided redlined plans and reports illustrating clarification to comments included within this report and other minor comments to be addressed. Comments within these redlined documents shall be fully addressed. The redlined documents shall be returned to Staff and must be included with the resubmittal for it to be considered complete. 2. The application was referred to SEMSWA, UDFCD, and CDOT for review. A response to comment letter is required for all comments issued by the County, SEMSWA, UDFCD and CDOT. 3. RESUBMITTAL PROCEDURE - Attached to this report are instructions to the applicant regarding the resubmittal of documents. The applicant and their consultants must follow these instructions explicitly to avoid delays in our and processing of this case. Specific Development Plan 1. Include the Arapahoe County Case No. P in the lower left-hand corner of the plans. 2. Please clearly show and label the floodplain delineations and call out the source of designation. 3. Make text legible for all tracts. 4. Ensure Pond E is outside of the floodplain. 5. Label the elevation on the contours. 6. Need to include Floodplain in Land Use column. 7. Add a section line as a reference to Monaghan Road north of the project site (within the Sky Ranch Development but outside of the Neighborhood B). The ROW dedication to this portion of the roadway should be submitted to the County for review through a separate document. 8. Phage 3: need to verify if the proposed roadway connects to the north or it should be end at the property line (see redline comment on Sheet 3). 9. Public Urban Local Roadway Cross Section: change the sidewalk dimension to 5. Final Plat 10. Include the Arapahoe County Case No. P in the lower left-hand corner of the plans. 11. General Notes #3 and #5: FEMA FIRM Panel No C0206K has been revised; please change all references to Panel No C0206L (effective February 17, 2017). Base elevation is determined at the project location. Please revise the note as necessary 12. Recommend providing a key map on sheets 5 to An easement chart that included easement dedicated by the Plat shall be shown. The chart shall include the type of easement, its intended use, the grantee, the entity responsible for surface maintenance

6 14. Tract Summary Table: include the use of Floodplain in Tracts H and N, and include the use of emergency access in Tract U. 15. Show and label the 100-year floodplain easement. Call out the source of designation. 16. Show and call out the drainage easement for Pond E. Please know that Pond E is located outside of the floodplain. 17. AE means access easement, correct? Phase II Drainage Study 18. Include Case No. P on the cover sheet. 19. Nee to focus more on the Neighborhood B (Basins D-1, D-2 and E-1) drainage condition - more detailed sub-basin delineation and its drainage conveyances. 20. Runoff Coefficients (C): the C values were updated in March 2017 per UDFCD, Urban Storm Drainage Criteria Manual Volume 1. Please revise the drainage calculation accordingly. Traffic Impact Study (TIS) 21. Unclear if the emergency access to the site has been finalized with the Bennett Fire Protection District. If so please include the discussion of emergency access. 22. Page 2: typo appears in the first paragraph change Neighborhood A to B. 23. Page 8: Include the text of No further development beyond the 774 units will be permitted until the completion of the CDOT 1601 process for the Airpark Road and I-70 Interchange improvements at the end of Note 16. Floodplain Modification Study 24. Revise the tilt to Sky Ranch, Tributary T-9 to First Creek Floodplain Modification Study. 25. The applicant must address both SEMSWA and UDFCD s comments

7 Engineering Documents Required for Resubmittal to the County Engineering Services Division A copy of this Resubmittal Checklist Completed Review and Approval Form (Arapahoe County Form 581) available online at Completed Review and Approval Grading, Erosion and Sediment Control Form (GESC Form 403) available on-line at Copy of Latest Proposed Land Development Plan - (SDP, FP) Traffic Impact Study Phase II Drainage Study Floodplain Modification Study Engineering Cost Estimate Operations & Maintenance Manual Any comments to Stormwater Facilities Maintenance Agreement? Construction Drawings Pavement Design Report Grading, Erosion and Sediment Control (GESC) Plans & Report Legal Description and Exhibit Legal name, legal address, and title (if any) of the Owner, assign, or person with signatory authority on behalf of the Owner Exhibit that illustrates easement location(s), see comment #xx Geotechnical Study / Preliminary Soils report Collateral Letter of Intent Electronic files for set of plans being submitted to LandUseSubmittals@arapahoegov.com and cc to sliu@arapahoegov.com County Redlines for: FP, SDP, Phase II Drainage Study, TIS SEMSWA Redlines for: Phase III Drainage Study, GESC, O&M Manual, CDs Letter of point-by-point response to this comment letter and SEMSWA s comments Fees Due: Digit al x x x x x x x x x n/a Case No. P P Case Engineer: Sue Liu In order to expedite this case in an efficient manner, please provide all the items above to the Engineering Services Division counter at 6924 S Lima Street or all files to LandUseSubmittals@arapahoegov.com and cc to sliu@arapahoegov.com Incomplete resubmittal packages will not be forwarded to the case engineer for review until all of the information requested on this form has been provided. This sheet must be attached to your resubmittal with the revised documents in the quantities listed above

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