Presentation on theme: "Getting Caltrans to Approve Your Plans Basic Drainage Policies and Requirements Roy H. King, MS,PE California Department of Transportation Division of."— Presentation transcript:
Getting Caltrans to Approve Your Plans Basic Drainage Policies and Requirements Roy H. King, MS,PE California Department of Transportation Division of Hydraulics
Getting Started IGR (Inter-Governmental Review) – Optional but HIGHLY RECOMMENDED! Environmental Processing and Approval Research (Encroachment Permit Required for ALL WORK within Caltrans Right-of- Way!)
Plan and Permit Processing Plan Submittal (PS & E Package, including Drainage Report) Plan Review and Approval Construction
Why Can’t I Do That? Mandated / Restricted Use of Highway Funds and Right-of-Way Longitudinal Encroachments
REMEMBER: We Have High-Speed Traffic! (Affects ALL FACILITIES on our Highways!) Affects DESIGN!
Caltrans Drainage Considerations On-site Drainage Off-site (Cross) Drainage California Drainage Law Existing / Future Storm Drain Systems FEMA and Flood Plain Issues
On-Site Drainage No more than 0.1 cubic foot per second during a 25-year frequency storm allowed as concentrated flow anywhere within the traveled way. No water allowed to pond into the traveled way during a 25-year frequency storm.
Off-Site Drainage No formal written policy for design of culverts. Informal Policy: 100-year storm flow may not pond to the edge of traveled way; 10- year storm may not cause the culvert to seal or flow under pressure.
FEMA Issues Is there a FIRM map for any of the watercourses near your project? Will your proposed construction potentially raise the water surface by one foot or more? If so, you will need to prepare a LOMR or CLOMR - and: - Even if there is no FIRM map, you still might have to prepare a LOMR or CLOMR!
Recent Problem # 1 Where water previously flowed well outside the traveled way, the installation of curb and gutter now forces this water into the highway.
Existing ground probably capable of conveying 50-60 cfs before water reaches traveled way Reduced carrying capacity as a result of the curb and gutter – will carry maybe 10-15 cfs before water flows into traveled way
Even in a minor storm, note how little runoff it takes to pond to edge of traveled way But now—let’s put in some curb and gutter!
Recent Problem # 2 In the desert, our old two-lane rural roads would pond to a depth of four inches or so before water would flow across the road. Now that we’ve added two lanes and a shoulder, it ponds to a foot and a half!
Water ponds to only a few inches depth before spilling over centerline
But now, let’s add two twelve foot lanes (giving us three) at 2% crossfall, a ten foot shoulder at 5% crossfall, and look how deep the water ponds!
A More Serious Recent Problem: New development, while retarding the 100-year storm to less than pre- development conditions, has increased the flow from small storms. The increased flow from these small storms is KILLING us!
The flood routing calculations showed this basin would work just fine! (Did the outlet plug?) Were the Contractor’s BMP’s functioning properly?
However, the 5-year post-development runoff of 85 cfs was NOT reduced to the pre- development 5-year runoff of 50 cfs! The basin was designed to reduce the 100-year Q from 250 cfs post-development down to 175 pre-development—and will work just fine in a 100-year storm!
So where did the extra concentrated runoff from the basin outlet go?
This is how it looked when it got to the next major highway junction…