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Home My WebLink About20200186 Ver 2_Letter to Blake Guffey NCDOT - Apple Creek Culvert_20200215Alfred Benesch & Company 2018 Eastwood Road, Suite 111 Wilmington, NC 28403 www.benesch.com P 910-344-0143 June 14, 2020 Mr. Christopher Guffey, PE – District 1 Engineer Division 12 – NC Department of Transportation 1702 East Marion Street Shelby, NC 28151 Ref.: Apple Creek Corporate Park - letter of explanation regarding design of the culvert crossing at an unnamed branch creek crossing the R/W in design. Reasons and description for variation to standard design and request for approval Via: Electronic transmission (only) Dear Mr. Guffey: Thank you for working with us so closely on this project - and Mr. Clary as well - who, for the last 5 years, has been with us through the concept and design. As you know the culvert crossing we have designed along the new Apple Creek Parkway is a little different than the typical NCDOT culvert crossing for a roadway of this nature. Gaston County (funding is completely by the county) is seeking to construct a best-in-class Corporate Park campus feel complete with physical and performance features designed to be attractive to tenants in the park and to the public while maintaining all the safeguards necessary to protect the public’s safety, health, and welfare. This will be an economic engine for prosperity moving into the future for the county. I am writing you today to go over some of the reasons we have submitted the design that we did and wanted to communicate expressly to you some of the facts and at the end some assurances for NCDOT in this regard. We hope that you will share this letter with your reviewing departments in Raleigh – and that they may grant permission to proceed (subject to comments of course) as we have designed. Environmental Impact – minimizing permanent impacts to the landscape Our design considered several environmental factors. One of the most important issues related to the amount of disturbed and impacted area would be to create a smaller culvert footprint at the relatively small creek crossing and minimize those impacts functionally and visually. The unnamed tributary to Long Creek that we speak of – at this time – is less than 10’ wide at its widest banks. It is channelized - the normal stream elevation is down some 6’ within the banks currently. We sought to design a box culvert design with openings set at appropriate elevations to handle normal flow as well as the 1% storm flow Vehicle will be safely conveyed across on the new Parkway with a minimal permanent impact on the area. All calculations and empirical modeling for the culvert were done prior to beginning design to insure no significant impact to the area in terms of flooding or stormwater. The largest impact would be the construction of the culvert itself (which if course is temporary). The linear disturbance afforded us in the design of the culvert is approximately 150’* - utilizing the permitting we are in process of obtaining with USACE and NCDEQ. Although we are within these design limitations, mitigation is being required by the USACE for what we are doing to the added expense of Gaston County. Letter to Christopher Guffey, PE District Engineer – Gaston/Division 12 NCDOT Apple Creek Corporate Park – Letter of explanation Culvert Crossing June 14, 2020 Page | 2 *As a footnote the maximum linear footage of disturbed stream is less than it would be normally at 300 lf. However, the USACE is considering past partial development of the land and a previous permit (obtained by previous owner and expired) as part of the 300 feet – “cumulative impacts” which leaves our project with approximately 150 lf to work with. Aesthetic Design – architectural continuity within the park Elements of the culvert design are enhanced to provide a visually pleasing appearance of a culvert design reminiscent of older days and reflective of the rural farm community and give the feel of a bridge. Walls on the sides of the culvert will be stone veneer up to the railing to warm the appearance of the design. The poured in place concrete design is integral structurally and allows for a reduction of long expanses of cleared and graded areas that would widen the entire area and remove more of the natural stream including trees that line its banks currently if the walls are lessened or removed from the top of the culvert. In addition, we considered the elevations needed for good road design considering a significant portion of traffic will be tractor trailer trucks in the park. We sought to minimize slopes in the area of the culvert and balanced the elevations as much as we could as the approach from hwy 275 has been elevated to match the northerly side of the park more closely so the feel at the culvert crossing is fairly level. Lowering the elevation of the crossing will have not only a significant visual impact on the iconic nature of one of the parks centerpieces of design, it will also increase the slopes of the road into and out of the culvert. Design Basis and Description – Engineering The cast-in-place reinforced concrete box culvert was designed with taller headwalls in lieu of extending the length of the culvert as specified in NCDOT Structure Design Manual Section 9.2.1 for the reasons listed above. The cast-in-place headwalls are designed as retaining walls, strengthened with counterforts that extend down and connect into the culvert walls to provide the headwall with additional stability. On top of the headwalls, NCDOT standard two bar metal rail is anchored to the top of the upstream and downstream headwalls to provide for vehicular safety in case of collision with the barrier. The headwalls are designed to retain the earth fill on top of the culvert and withstand an associated live load surcharge. It is also designed to withstand a TL-2 impact to the two bar metal rail, in accordance with the AASHTO LRFD Bridge Design Specifications for local/collector roads. The cast-in-place reinforced concrete wingwalls are separated from the headwalls by expansion joint material, and thus function as a separate structure from the culvert and headwalls. The wingwalls are designed to retain the earth fill behind the walls and withstand an associated live load surcharge. All wingwalls are supported on footings on driven H-piles, some of which are battered to provide lateral resistance to the earth loads. Conservative assumptions were made regarding the soil properties due to unavailability of soil data in the area, so there may be an ability to reduce the number of piles when geotechnical information is available. Our culvert design was completed by our Raleigh NC office, Alexander Forfa headed up the design and is engineer of record for the culvert. Technical questions relating to his design may be presented to him directly (copy me please). His contact information is 984.275.2493 (o), 516.320.5660 (cell), or email is aforfa@benesch.com. Letter to Christopher Guffey, PE District Engineer – Gaston/Division 12 NCDOT Apple Creek Corporate Park – Letter of explanation Culvert Crossing June 14, 2020 Page | 3 Other important considerations – financial responsibility long term Gaston County has agreed, in addition to guaranteeing maintenance within the right of way for everything other than paving and curb, to assume responsibility for maintenance of the culvert crossing and will do so in written agreement with division 12 incorporating this into maintenance agreement to follow. Our schedule for this project is very aggressive as marketplace demand already has allowed the Gaston EDC to contract with two international build to suit projects on the northerly end of the project (about a mile from the culvert crossing). However, there is adequate time to compete the approval process for the culvert crossing portion of the work this summer – as the contractor does not anticipate beginning work in that area of the project until after August. I hope this letter helps to clear up any confusion or doubt as to the intentions for our project. Our project, including this culvert, has now been bid and a contract awarded to a prime general contractor- Neill Grading Company from Hickory NC. Their subcontractor for the construction of the culvert crossing is one that you are very familiar with, Dane Construction. We eagerly await word as to the acceptance of our design basis for this culvert. Our permit for Wetland Disturbance is being held by NCDEQ pending the decision that no significant changes to the footprint of the culvert will be required. Please feel free to contact me with any additional requests for information or comments. It has been a pleasure to work with your team on this project and we look forward to the coming year and getting the project completed in 2021. Sincerely, Alfred Benesch & Company Benjamin Simpson, PLA, ASLA – Sr. Project Manager I Associate Copy: Greg Stewart, PE , Raleigh NC Office Manager Donny Hicks, Executive Director, Gaston EDC Wesley Clary, Asst. District Engineer, District 1/Division 12 – Shelby Alex Forfa, PE, Structures Design Engineer, Alfred Benesch & Company Kevin Westra, PE, Design Engineer, Alfred Benesch & Company Mike Iagnocco, PE, - STV (Wetland Permitting Consultant) Morgan Woolner, Designer, Alfred Benesch & Company Richard Callahan, Designer, Alfred Benesch & Company Brian Ralstin, PE, Design Engineer, Alfred Benesch & Company Brian Gaffney, PE, Design Engineer, Alfred Benesch & Company