Q: What type of new stream-crossing structure does the Program or Center recommend?
Anything but a smooth-bore round plastic pipe if possible!
Round smooth-bore plastic pipes may be cheap, but they are almost incapable of holding streambed material. Increasing the size of a round pipe can also lead to problems with getting adequate pipe cover without significantly raising the road elevation. In today's market, a wide variety of structures exist to provide better crossings, many of which are wider than they are tall, which helps in handling
the bankfull channel w
raising the road. There is no "magic bullet" structure that will fit every situation. Factors such as channel slope and bed material, scour potential, road elevation, expected debris flow and bedload movement, and anticipated traffic loads all factor in on the decision. Some general structure categories include:
"Squash" pipes: Oval or elliptical pipes that function better than round pipes, but usually not by much.
Relatively expensive but easy to install rectangular structures typically made of concrete. While they can be used effectively, box culverts often have difficulty retaining stream bed material and can create their own issues with aquatic organism passage.
Arch Pipes: A general term for a wide variety of metal plate structures that have
very flexible design parameters, and can be installed with our without footers and plate bottoms.
: Don't overlook the potential for turning some culverts into small bridges. It may be less expensive than you think with technologies such as Geosynthetically Reinforced Soil abutments and timber decking.
Center for Dirt & Gravel
Larson Transportation Institute
Penn State University
201 Transportation Research Building, PA 16802
The Center provides education, outreach, and technical assistance related to PA's Dirt, Gravel, and Low-Volume Road Maintenance Program.
Support provided by:
PA State Conservation Commission
2017 Annual Workshop
Planning is underway for the Center's 2017 Maintenance Workshop in Sayre, PA on September 26-28th. The Workshop will follow a similar format to the past two years, with optional trainings and field trips on the 26th, concurrent class sessions, field trips, and a banquet on the 27th, and more field trips and a brief wrap-up session on the 28th. A preliminary agenda can be found on the Center's website
. A more detailed agenda and online registration will be available soon.
2016 Annual Summary Report Available
The State Conservation Commission DGLVR Program 2016 Annual Report is now available. The report summarizes projects, spending, and practices for the 2016 construction season. It also includes a 2-page insert about the 20th Anniversary of the Program. Hard copies of the report will be mailed to Conservation Districts and other Program-affiliated entities once printing is complete. In the meantime, a PDF of the report can be accessed on the Center's website here.
Stream Crossing Trainings Held Across PA
The Center partnered with Trout Unlimited this Spring to hold a series of trainings on determining bankfull and implementing better stream crossing replacements. With 80 stream crossing replacements reported in the DGLVR Program in 2016, and more expected in 2017, the proper
of these crossings is an increasing priority. These trainings condensed a lot of information into a short period, and focused on important factors in
stream crossing replacement such as slope measurements, structure choice, and channel grade control. Special thanks to Phil Thomas of Trout Unlimited for his help with these trainings.
All of the presentations, handouts, and videos used in the training are available on the Center's website
Training attendees survey a stream in Cameron County
Driving Surface Aggregate Testing
Below are some clarifications in regards to frequently asked questions about Driving Surface Aggregate testing for SCC-funded projects:
- Piles of DSA are approved, not entire quarries.
- Testing should be done on complete piles if possible. A 8,000 ton job should not be approved by only testing a 500 ton "test pile".
- A single DSA pile can be tested once for multiple jobs, even across county lines. Several tests may be required on extremely large piles to make sure the sample is representative of the entire pile.
- If new DSA material is added to an existing DSA pile that had already been tested, the new pile should be mixed and tested again.
- Stockpiling of DSA prior to placement by the applicant or contractor is highly discouraged. Stockpiling leads to additional aggregate segregation, and makes it nearly impossible to control moisture. Once material is stockpiled, the quarry is no longer responsible for moisture or mixing to avoid segregation, both of which are required in the DSA specification.
- Conservation Districts can perform DSA sampling for their projects, and the costs of sample testing can be built into project grant costs, or covered by CD administrative funds.
- Someone from the CD should be on site when DSA placement begins to insure the DSA is well mixed and at the proper moisture.
- Please call the Center, allowing as much lead time as possible, for assistance with sampling or placement.
Driving Surface Aggregate pile at a quarry
ESM Trainings in Full Swing
The Center's 2017 Environmentally Sensitive Maintenance trainings are underway with eight completed and four more scheduled for 2017. Attendance has picked up slightly compared to 2016, and feedback has b
een positive about the training course changes and additions completed over the Winter of 2016-17. Just a reminder th
at all NEW potential grant applicants must attend a 2-day ESM training to obtain their initial certification to apply to the Program, which lasts for five years. Once a potential applicant is certified, they may choose to attend either another ESM training, or one of the Center's Annual Maintenance Workshops, to renew their certification for another 5 years. More information, including a list of dates and locations, an attendee certification list, and online registration, is available on the Center's website
In Other News...
This recurring feature highlights related topics outside the Program.
The Center began testing dust production from unpaved roads in the summer of 2015 using a vehicle-mounted particulate monitoring system. The primary research objective was to compare dust production from Driving Surface Aggregate (DSA) developed by the Center for Dirt and Gravel Road Studies (Center) to other commonly used road surface aggregates in Pennsylvania such as PennDOT 2A and 2RC. In both the initial monitoring system testing in 2015, and the aggregate performance research conducted in 2016, DSA roads always outperformed 2A and 2RC road surfaces, and generally produced less than ½ the dust.
Visual comparison of dust on DSA -vs- 2A
A GoPro camera was mount
ed on the rear of the vehicle to visually track dust production. The photograph on the left shows the dust production from the DSA section of Laurel Run Road in Rothrock State Forest compared to the 2A section on the right.
All DSA road sections significantly outperformed the 2A road section in suppressing vehicle generated dust. Notably in the chart below, DSA 1 placed in
2012, which would not meet our current specification,
still produced significantly less dust than the 2A section. More details of the dust measurement system and associated research can be found on the Center's website here.
Quantitative dust measurements of DSA and 2A surfaces.