1. Critical Stages – What is required on the plan and in the field
NPDES & PCSM Permitting Workshop
May 24, 2016

2. 102. 8(k) Licensed professional oversight of critical stages
102.8(k)  Licensed professional oversight of critical stages. A licensed professional or a designee shall be present onsite and be responsible during critical stages of implementation of the approved PCSM Plan. The critical stages may include the installation of underground treatment or storage BMPs, structurally engineered BMPs, or other BMPs as deemed appropriate by the Department or the conservation district.
When PCSM BMPs are being constructed/installed, the regulations require the critical stages to be observed.
The critical stages are important to make sure that the BMPs are built properly. Why go through the steps of designing the BMPs if they are not built properly, as then stormwater runoff would not be managed properly.
A licensed professional of their designee shall be present onsite and responsible during critical stages of implementation. The designee has to be someone with the training and experience to know whether or not the critical stage is being properly implemented.
The critical stages are observed as they are being done. It is not a stop out at the site for 1 hour to look, the licensed professional has to be onsite during the full implementation of the critical stage; if the critical stage takes 4 days at 12 hours each day, then the licensed professional or their designee has to be onsite and responsible for those 4 days and 12 hours each day.
They have to be responsible, which means that if the contractor isn’t following plan, then they have the authority to stop the contractor and tell them how to do the critical stage properly.

3. 102.1 Definitions Licensed professional—Professional engineers, landscape architects, geologists and land surveyors licensed to practice in this Commonwealth.

4. What is this important?
BMPs that can’t be inspected once the BMP is constructed, must be inspected during construction.
More examples: Most BMPs listed in Ch. 6 such as: underground storage BMPs, infiltration trenches, subgrade, basin berms, anti-seep collars, impervious core, concrete cradles, key trench installation, bmps deemed appropriate by the DEP or CD, etc.
A critical stage of installation can be boiled down to; “can DEP and/or the District go out after installation and visually observe that the BMP was installed properly? If yes, then it is not a critical stage.”
An example of a critical stage would be an infiltration trench, as DEP cannot go out an tell that it was installed or that it was installed to the appropriate specifications.

5. Oversight should include: Maintaining ESPC BMPs during construction
GW or rock encountered (that was not part of the design)?
subgrade preparation per approved plan
Built per details (proper fill, compaction, engineered soil,etc.)
“Construction Sequence” section of the PCSM manual provides good oversight guidance
Best to install pcsm during later phases
Protecting infiltration areas from compaction….this is critical
Ensure geotextile is installed properly
Underdrains installed properly
Was proper stone used as per spec….clean, uniformly graded
Chestnut Hill infiltration basin

6. A list titled “PCSM Critical Stages” should be located on the PCSM plan drawings with all the critical stages listed.
Also required in Section D of the application
Also good to identify these stages in the construction sequence to prompt the contractor.
PCSM Critical Stages
Complete basin construction including subgrade preparation, berm and barrel installation
Complete infiltration trench construction

8. The infiltration bed was designed to have approx
The infiltration bed was designed to have approx. 5 to 15 feet of fill on top of the stone bed.
The infiltration bed was proposed with laterals to feed the bed.
The construction sequence included provisions to manually block off the laterals during construction to avoid the potential for sediment laden runoff from entering the laterals.

9. The engineering consultant notified DEP that sediment laden runoff had entered the stone bed during construction.
When DEP investigated, it was found that the contractor was not following the construction sequence by manually blocking off the laterals, the licensed professional’s designee had left the site early that day and that the contractor was trying to beat the forecasted rain storm.

10. You can see the sediment stained stone and the stone that was already placed and had the filter fabric placed down.

11. This is a picture of the stone around one of the previously placed laterals. You can note the clean stone at the top of the bed, but when they dug down to the lateral and below, they found heavy sediment in the stone bed.

12. Example Critical Stage & NOT
Testing
Initial proposed fix
Ultimate resolution
The engineering consultant had done some “testing” on the sediment stained stone. Which consisted of placing the stone in a 5 gallon bucket that a crack down the side, and then pouring water over the stone. They said that the water out of the crack wasn’t discolored. Therefore, the sediment was going to stay attached to the stone.
They proposed to cleanout the laterals, replace the open stone cell, but only to 6 inches above the bottom of the bed and to add an additional 2 cells to the side of the bed.
DEP determined that the test was not adequate. It wasn’t based on a scientific test, it was done with pouring water over the stone; where the actual conditions would have been water soaking around the stone, and the water used for the “test” was cold; where the anticipated water temperature would be hot; which would cause the soil to be more soluble.
The issue that DEP had was that the entire bed was now sediment laden and had serious concerns about the viability of the BMP.
The proposed fix did not address the sediment throughout the entire ned, as that would eventually settle to the bottom and clogging the system.
DEP identified that the Permittee had 2 real options to them; 1) to replace the BMP with another BMP at the site, or 2) completely remove the infiltration bed and reinstall it with clean stone per the approved plan; which the Permittee identified would cost about $500,000 to do.
Due to the Permittee’s schedule to complete the project, they selected the second option. To remove the previously installed/constructed infiltration and install a new bed with clean stone.
The lesson learned here is to ensure that the contractor is following the construction sequence, the licensed professional or designee is onsite for critical stages, don’t try to beat the rain, design and install E&S BMPs to address sediment laden runoff from entering an infiltration BMP.

13. Here is a picture from a project in South-central PA
Here is a picture from a project in South-central PA. You can see that the infiltration area is completely surrounded by silt fence to protect it form sediment laden runoff.
This is an inexpensive assurance that could be considered to ensure that no sediment laden runoff enters the infiltration area during construction. This could be included in the construction sequence.

14. TO BE COMPLETED BY LP RESPONSIBLE FOR CRITICAL STAGES
102.8 (l)  Final certification. The permittee shall include with the notice of termination ‘‘Record Drawings’’ with a final certification statement from a licensed professional, which reads as follows:
 ‘‘I (name) do hereby certify pursuant to the penalties of 18 Pa.C.S.A. §  4904 to the best of my knowledge, information and belief, that the accompanying record drawings accurately reflect the as-built conditions, are true and correct, and are in conformance with Chapter 102 of the rules and regulations of the Department of Environmental Protection and that the project site was constructed in accordance with the approved PCSM Plan, all approved plan changes and accepted construction practices.’’ (ITEM 5 ON N.O.T. FORM)
TO BE COMPLETED BY LP RESPONSIBLE FOR CRITICAL STAGES

15. QUESTIONS? Mark Lonergan PA DEP Reading District Office Bureau of Clean water (610)