WCD Engineers Workshop - westmorelandconservation.org
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WCD Engineers Workshop Friday, March 26, 2021 Chapter 102 Discussion of Stormwater Management By James W. Pillsbury MS PE [email protected]
Transcript of WCD Engineers Workshop - westmorelandconservation.org
WCD Engineers WorkshopFriday, March 26, 2021
Chapter 102
Discussion of Stormwater Management
By James W. Pillsbury MS PE
Stormwater Management
Module 2
Excel Spreadsheets
Common Stormwater Errors
In addition to Module 2, you also need drawings and calculations and a narrative.
Post-Construction Stormwater Management Module 2
• Discharge Points
• BMP’s
• Sequence of Construction
Post-Construction Stormwater Management, Module 2
• Geologic Conditions
• Thermal Impacts
Post-Construction Stormwater Management Module 2
• Stormwater Analysis—Runoff Volume
If you submit the DEP Excel PCSM Spreadsheet, you can skip questions 5-9.
Post-Construction Stormwater Management Module 2
This section must be completed for any BMP that proposes infiltration.
Post-Construction Stormwater Management Module 2
• If you submit the Excel™ PCSM Spreadsheets for Volume, Rate, and Quality, you may omit answering some of the Module 2 questions
• Regarding Volume, if the applicant chooses not to use the PCSM spreadsheet, they may use the material from Chapter 8 of the 2006 SWM Manual or another approved alternative.
• Submitting the Excel™ PCSM Spreadsheets will simplify WCD’s review of your plan.
Stormwater Management
Module 2
Excel Spreadsheets
Common Stormwater Errors
DEP’s Excel Spreadsheets, latest version, strongly recommended for use
Sometimes you get an error message. Remember that data you enter is used on later slides and so the program catches “errors” you may make… Try again!!
DEP’s Excel spreadsheets… work your way through them in order!
Data you enter on General will be used on the other spreadsheets
Volume spreadsheet, top portion… enter land cover information here
Volume spreadsheet, middle portion, it calculates requirement for you
Volume spreadsheet, bottom portion: are you OK or not??
Looks like we are NOT OK.We will have to adjust our BMP’s!
Enter data for your BMP’s.
Volume Control: now we are OK.
You have to work with it back and forth!!Make sure you take the credit you can from your various BMP’s.
Rate worksheet requests precipitation amounts, and then you can choose whether you want the spreadsheet to calculate time of concentration or not. If not, you can choose ‘default’.
The program uses a version of TR-55 to calculate peak flow rates. If you enter your own rates, you will need data from a program to back it up for the reviewer.
Using tc and precipitation info, the spreadsheet calculates peak discharge rates pre and post.
The program won’t work if you calculate pre tc but ask it to do default post… so you have to calculate both pre and post tc, or do default both pre and post
Rate worksheet summarizes the function of BMP’s.
Rate control worksheet does not calculate orifices, spillways, pipes, etc.You have to do that yourself and provide the input for the table. Remember to show your work for the reviewer!!
Water Quality spreadsheet is required.
Pollutant load and required reductions are calculated.This takes the place of old Worksheets 12 and 13.
The Quality spreadsheet calculates the effectiveness of the BMP’s.
You have to sign the box!
Looks like we are OK. If not, you need to add BMP’s.
Stormwater Management
Module 2
Excel Spreadsheets
Common Stormwater Errors
A common stormwater management error:
WPXI
Another common stormwater management error:
Common SWM plan problems
• Riser calculations don’t match the drawing
• Energy dissipaters on steep slopes
• Time of concentration path not representative of watershed
• Not enough inlets or poor location of inlets
• Notice of Intent errors
Riser elevations need to match the calcs
You are Cordially Invited…
Mr. James W. Pillsbury, MS, PE, cordially invites you to Draw Your Riser to Scale!
Placing energy dissipaters on a slope is a frequent SWM error.
The assumptions with this nomograph are that the pipe slope and the slope of the dissipater both, are relatively flat—say, <2-3%
To dissipate energy from a steep slope pipe, use a drop manhole or a T-outlet.
To dissipate energy from a steep slope pipe, use a drop manhole or a T-outlet.
Are your velocities reasonable?
Are your Manning’s n’s reasonable?
Did you choose the right surface?
Time of Concentration flow path should be representative of the drainage area.
Most of this watershed is agricultural.
Sheet flow was started in the one paved area way up at the top of the watershed.
That gave an artificially fast time of concentration.
Time of Concentration flow path should be representative of the drainage area.
This one will have an artificially long time of concentration.
Stormwater escaping past inlets due to poor pavement contours or curb issues
Not an engineering or design error, but you need to anticipate it and design redundantly
Notice of Intent (NOI) common errors
• Use the most recent forms!
• Don’t leave anything blank
• Project and Applicant information
• Site Restoration?
What is a site restoration project?
• Pipelines and utilities
• Certain resource extraction activities
• Site reclamation
No new impervious surface created
Notice of Intent… stormwater discharge information
Is your receiving stream impaired by siltation, sediment, turbidity, water/flow variability, flow alterations/modifications, or nutrients??
Is there a TMDL for your receiving stream, for siltation, suspended solids, or nutrients??
ABACT BMP’S
Be sure you find the right stream: HQ & EV
Beaver Run above dam
Indian Camp Run
Miller Run
North Fork Mill Creek
Coalpit Run
LoyalhannaCreek above Laughlintown Run
Laughlintown Run
McMullen Run
Furnace Run
Spruce Run
Trout Run above Blairsville reservoir
ShireyRun Baldwin
Creek
PowdermillRun
Poplar Run
TubmillCreek above dam
Indian CreekSewickley Creek
above Brinker Run
Long Run/Jack’s Run White Oak Boro
Steele’s Run
Haymaker Run
NOI Checklist
• Check a box on every line
• Include everything that is Applicable
NPDES Permits + Applications are available on our website!
Finding the NPDES permit documents
Stormwater Management
Is your friend.
Jim Pillsbury
Westmoreland Conservation District
www.westmorelandconservation.org www.westmorelandstormwater.org
