National Society of Professional Engineers

1. National Society of Professional Engineers Drainage Study Submittal Requirements Clark County Regional Flood Control Design Workshop By: Jeffery J. Jensen, P.E. - Civil Engineering

2. Introduction • Seminar Goals • How do Obtain Prompt Drainage Study Approvals? • When is a Drainage Study Required? • What are the County Review Expectations? • What is considered a complete drainage study? • What are the most common mistakes? • Come to Understand - You should have been a Structural Engineer!

3. Reasons for Drainage Study • Purpose/Overall Goal: Protect Life, Property and the Public Interest from Flooding • Examples • Protect Life – velocity x depth < 6 • Protect Property – FF is 18” above road • Protect Public Interest – drainage easements

4. Reasons for Drainage Study (cont.) • Define the impact of development to adjacent properties • Address the amount of runoff impacting the site • Address mitigation measures • Provide legal record the of review process and issues resolved

5. Drainage Study for Subdivision Maps in Clark County NV • Major Projects (negotiation engineering) • Major Subdivision Maps (Final Maps or NFM) • Always require a drainage study • Minor Subdivision Maps (parcel maps) Drainage Studies: • Establish finished floor elevations • Determine if upstream flows need to be routed through site within a drainage easement • Provide positive drainage for site (i.e., no “ponding” of water) • Create public document for future research • Single Family Home (PAC) • Rarely require a drainage study

6. Drainage Study Warrants • Improvements are proposed on a parcel • Absolute (A) – will require a drainage study • Exceptions • Subjective (S) – a drainage study may or may not be required based on particular conditions

7. Drainage Study Warrants (cont.) • Absolute: • Parcel is in a flood zone • Parcel is adjacent to a proposed/existing Clark County Regional Flood Control District (CCRFCD) facility • Major subdivision (a.k.a. Final Map FM or New Final Map NFM) is proposed • Major subdivision is five (5) lots or more • Note – will require drainage study on multiple minor subdivision maps (MSM) which are being proposed to avoid FM requirements

8. Drainage Study Warrants (cont.) • Absolute (cont.): • A Notice of Final Action (NOFA) from Board of County Commissioners or Planning Commission indicates a drainage study is required • Unless a waiver is obtained • Drainage Study Update (cha-ching factor) • Overall drainage study approved but some parcels within study not completed will require an update • Need to query the Final Approval Letter in county image database to determine if case applies

9. Drainage Study Warrants (cont.) • Subjective (may or may not be necessary): • Parcel is in a natural wash (aerial photos show major drainage issues), usually requiring a technical drainage study • Drainage study previously required on neighboring/surrounding parcels • Historic flooding problems/Drainage Complaints – rely on history and experienced staff to make the call

10. Drainage Study Warrants (cont.) • Subjective (cont.): • Single parcel is being subdivided into four (4) lots (MSM) usually requiring a drainage study to resolve all drainage issues on all four (4) proposed lots • Site is extremely flat and will have difficulty in draining • Basements (needs to be approved) • No residential basements allowed in a flood zone • Will always require a finish floor waiver from Civil Engineering • If no other drainage issues are present, then a drainage study maynotbe required

11. Items to Include a Drainage Study Report

12. Cover Sheet • Drainage study title* • Must match grading plan title • Include minor subdivision map in title • Prepared for: Developer Name • Address • Phone # • Fax # • Prepared by: Engineer Name • Address • Phone # • Fax # • Date (month/year) *Technical, Update, Addendum, Supplement

13. Forms • Standard Form 1 • http://breccia.ccrfcd.org/pdf_arch1/hcddm/forms.pdf • Standard Form 2 (Initial Submittal only) • Clark County Drainage Study Submittal Checklist • Dream is to combine • Not required for Updates • http://dsnet.co.clark.nv.us/dsweb/cd_pdf/drainage_submittal_cklist.pdf • Drainage Study Submittal Sheet • Used to update the Drainage Study location GIS layer • Only required at front counter (not bound w/study) • Used for HTE data entry – filled out by runner? • http://dsnet.co.clark.nv.us/dsweb/cd_pdf/drainage_submittal.pdf

14. General Information • Site Location • Township, Section, Range • Major cross streets • Assessor’s Parcel Number(s) • Any significant development or land features bordering site?

15. General Information (cont.) • Project Description • Purpose for study • Acres owned and being developed • Type of development (residential/commercial/industrial) • Number of proposed lots or proposed buildings • Proposed drainage facilities & off-site improvements • Type of improvement to perimeter streets • Right-of-way widths of proposed interior streets • Zoning requirements

16. General Information (cont.) • Clark County Regional Flood Control District (CCRFCD) Master Plan Information • Discuss the projects proximity to existing/proposed regional flood control facilities • Include figures (facility map and inventory list) from current master plan amendment (8/2004) *Note: If project is relying on CCRFCD facility, the facility must be substantially complete prior to permitting.

17. General Information (cont.) • RFCD Facility • If relying on facility to remove downstream flood zone • Structures at or above the Base Flood Elevation (BFE) – RFCD project just needs to be under-construction to obtain permits • Structures below BFE – then issues (St. Rose Court by PBSJ)

18. General Information (cont.) • Federal Emergency Management Agency (FEMA) Floodplain Information • Identify which flood-zone the proposed project lies within (Make reference to figure from current FEMA and Federal Insurance Rates Map panel) *Note: Current Federal Insurance Rate Map panels & Letter of Map Revision information can be downloaded from www.ccrfcd.org

19. General Information (cont.) • Hydrologic Procedures Used • Discuss the hydrologic methodology used in the study (Hydraulic Engineering Center, Rational Formula Method, etc.) • Hydraulic Procedures Used • Discuss the hydraulic procedures used in this section (Hydraulic Engineering Center- River Analysis System [HEC-RAS], Water Surface Pressure Gradient Software [WSPG], Highway Design Software, FlowMaster, etc.) *Note - Provide input and output data from the programs used - Provide figures showing cross section locations for channels & storm drain (include WSPG/HEC-RAS stationing on plan & profile) - Provide graphical cross section from HEC-RAS & FlowMaster

20. General Information (cont.) • Previous Studies in Project Vicinity • Discuss previous studies or reference studies that were used and/or reviewed in the analysis of subject site • Discussion should include what relevant parts were taken from each study and where the reference material is located • Highlight all pertinent information in the reference material • Include statement in text that you have reviewed and concur with findings of study *Note: - Approval letters from all referenced studies must be provided - The subject site must be delineated on any reference figures - Do not include entire reference study

21. Hydrology/Hydraulics Section of Report Model 3 time periods/conditions • Existing – no development • Interim – post or between development • Developed – proposed, ultimate build-out, everything developed • Design to worst condition

22. Hydrology/Hydraulics Section of Report (cont.) • Existing Condition hydrologic and hydraulic section of report should include discussion (with all necessary calculations, backup data, etc., in an appendix) of the following: • Watershed characteristics (general slopes) current density (land use) of off-site basins • Discussions of Hydrology Engineering Center (HEC-1) analysis with reference to basin map (Discuss combination points, routing, referenced flows not included in HEC-1, etc.)

23. Hydrology/Hydraulics Section of Report (cont.) • Existing Conditions (cont.): • Discuss existing drainage facilities (will subject site utilize existing facilities to mitigate on-site drainage) • Discuss if any existing drainage easements • Discuss existing flow splits • Pima County Method only for fully improved streets (curb & gutter) • Prefer – match water surface elevations • Discuss existing street flows • Make it better or same for downstream

24. Hydrology/Hydraulics Section of Report (cont.) • Existing Conditions (cont.): • Provide any necessary reference material (analysis, grading plans, etc.) for existing facilities • Discuss dry lane/depth velocity criteria in perimeter streets • ROW ≥ 80 ft

25. Hydrology/Hydraulics Section of Report (cont.) • Interim Conditions -“Interim” is defined as on-site being developed, the off-site as it currently exists • Discussion of hydrology • Discuss results of Hydrology Engineering Center (HEC-1) analysis and impacts proposed project has on surrounding properties. • What is proposed to mitigate impacts • Discussion of hydraulics • Discuss proposed onsite drainage patterns, proposed drainage facilities, and proposed drainage easements • Discuss existing vs. proposed street flow conditions

26. Hydrology/Hydraulics Section of Report (cont.) • Developed/Future Conditions -“Developed” is defined as on-site and off-site developed • Discussion of Hydrology Engineering Center (HEC-1) analysis • Provide summary tables and discussion comparing existing, interim and developed conditions • Discussion of hydraulics

27. Hydrology/Hydraulics Section of Report (cont.) • Developed/Future Conditions (cont.) • Discuss hydrologic/hydraulic impacts the proposed development has on surrounding properties (What is proposed to mitigate impacts?) • Do not substantially change downstream (this is best left to the experts RFCD and City of LV) • How will site be protected? (e.g. finished floor elevations, berms, walls, storm drain….) • Divert storm flow to ROW, check adjacent homes are flood protected • Again – should have been a structural engineer *Note: Site must be designed for “worst-case scenario”

28. Grading Plan • Shows off-site improvements • Ensures applicant is not grade-locking adjacent parcels • Is a common document in different revisions between Plans Check, Zoning, and Drainage • Must include any Structural Details

29. Grading Plan (cont.) • Include Plan and Profile when • Proposing storm drain • On exterior streets • Flat streets – longitudinal slope < 0.5% • Most important part of Drainage Study • Become check prints in Plans Check

30. Drainage Plan/Basin Map • Shows runoff drainage • Establishes runoff, cubic feet per second (cfs) • HEC-RAS, provide exhibit to verify topo • Storm drain – provide flow summary, amount capture in drop inlet, what remains in ROW • Label contours and basin concentration points

31. Drainage Plan/Basin Map (cont) • Provide exhibits showing Existing/Interim/Developed Conditions • Provide Hydrology Routing Diagram from HEC-1 or HEC-HMS • WSPG, verify stationing, match analysis to plan • Location of FlowMaster cross-sections • Must match grading plan • Summarizes all technical analysis

32. Drainage Review Feedback

33. Design Suggestions • Design site to minimize use of sidewalk drains • May require retaining wall or additional fill • Label all Finish Floor elevations • Use DDMS • Need to have Standard Form 4 match HEC-1 analysis. • Done automatically with DDMS • Use Concrete  • If using Rip-Rap, provide calculations

34. Common Drawbacks • #1 - Not addressing impacts to adjacent property owners and facilities • Should have been a structural engineer – only have to be concerned about your site • Failure to obtain permission to grade on neighbor’s property

35. More …Common Drawbacks • Not delineating easements and access to public easements • Airport – drainage conveyance area or ROW • Flows coming from Public ROW or > 30 cfs – provide Public Drainage Easement • Build to Public Standard • Provide maintenance access to proposed public facilities • Submitting incomplete Updates • Not including approval letter and grading plans from approved study • Not showing proposed changes on approved plan set

36. More …Common Drawbacks • Not meeting dry lane criteria • meeting the 19ft for 80’ right-of-way and greater • Provide final grading plan set • Not Public Works – don’t provide 30%, 50%, Pre-Final, Final, or Bid Set • Details • Always provide NDOT details in grading plan • Any revisions to the Clark County Area Uniform Standard Drawings (CCAUSD) – provide a detail

37. More …Common Drawbacks (cont.) • Not submitting quality assurance/quality control of submitted work • Need Senior to review work before submitting • Reference material(s) - don’t provide an entire study • Just to verify Q being accepted and adopted, so circle/highlight what is being referenced • Show referenced basins on Drainage Plan if not adjacent to site • Free copies from County if • KoVIS internet application is down • Black streaks in plan • Not including nuisance drainage mitigation • Downstream property must accept upstream storm flow, but not nuisance

38. More …Common Drawbacks(cont.) • Not using current Federal Insurance Rates Map (FIRM) Maps • Did a LOMR effect your site? • Provide Flood Zone Note • If no FIRM published use FIRM Index • Putting rip rap or berms in the right-of-way • Time of Concentration (Std Form 4) • Show Overland and Travel Time lengths on Basin Map

39. More …Common Drawbacks (cont.) • NDOT headwall - exceeding max retaining • Retaining Wall vs Flood Wall • Building Division reviews Retaining Walls • Civil Engineering reviews Flood Walls • Match drainage study to grading plan • Coordination issues – Engineering Firm A does drainage study and/or structural calculations, Engineering Firm B does the grading plan – don’t match

40. More …Common Drawbacks(cont.) • Love RCB and RCP • No 2-piece boxes (without structural details) • Not flood protecting your site from perimeter streets • Finished floor 18” above top curb/centerline • Having sidewalk drains used to drain parking lots, not landscape buffers (maintenance issues)

41. More…Common Drawbacks (cont.) • Stick it to my neighbor • Vacate my half of the ROW or BLM Patient Easement, attempt to put drainage channel/access ramp/easement on the neighbor’s half • Retaining Wall and discharge storm flow • Choose one, but not both • May require drainage easement • Increase velocity – provide erosion protection on your site, not the neighbor

42. Summary • Things to remember: • Put yourself in the neighbor’s shoes • Match Drainage Study to Grading Plan – is it reasonable? • Don’t underbid project • Quality, Money, Time Variables • Priority • Grading Plan • Drainage Plan/Basin Maps/Exhibits • Drainage Study Report

43. Summary (cont.) • Remember - you: • Are the Experts when it comes to your project • Are involved with your project on a regular basis • Need to ensure your submittal is clear and complete • County - we: • See projects only when plans are submitted and inspections are conducted • Are always looking for ways to improve our services to better serve you • Encourage Pre-Submittal Meetings • Add meeting notes with submittal • Always the Standard Answer – “… case by case”

44. Senior Engineers - Contact info • http://www.co.clark.nv.us/ • Gabriel Herrera, P.E. – 455-2453 GAH@co.clark.nv.us • Jeffery Jensen, P.E. - 455-0301 jjensen@co.clark.nv.us • Glenn Hale, P.E. - 455–4613 glenn@co.clark.nv.us