Practical Highway Design Solutions (2013)

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78 Appendix i Case examples of practical improvements for Kansas dOT

79 Example 1: ConsideringAlternate Scopes One recent example of considering alternate scopes was for a project on K-23, a low volume highway in Gove County. The sec�on of K-23 chosen for improvement was constructed in the 1930’s and 1940’s and has not undergone major reconstruc�on since its ini�al construc�on. It has a fairly straight and flat exis�ng alignment with li�le to no shoulders, and the pavement is deteriora�ng. The side slopes are generally 3:1 with rela�vely low fills tying into gentle to rolling terrain. The alternate scopes considered varied from “reconstruc�on” of the alignment to meet AASHTO criteria to “pavement replacement.” Proposed typical sec�ons are depicted in the following figures. Figure 1: “Reconstruction” Typical Sec�on Figure 2: “Pavement Replacement” Typical Sec�on For the “reconstruc�on” scope, K-23 would be rebuilt to meet current criteria. The horizontal alignment and the grade of the ver�cal alignment would only need slight adjustments to achieve geometric improvements. The exis�ng side slopes would be flattened to increase the safe recovery zone (clear zone) and the exis�ng pavement would be completely replaced. The proposed roadway would consist of two 12’ lanes and 4’ shoulders (3’ paved and 1’ turf). This op�on would take considerably longer to build than the “pavement replacement” scope and would cost approximately $1.2 million per mile to build. The “pavement replacement” scope would remove the exis�ng pavement and lower the

80 ver�cal alignment allowing a two-foot shoulder (with rumble strips) to be added. The proposed roadway would consist of two 12’ lanes and 2’ paved shoulders. Replacing the exis�ng pavement would allow the supereleva�on on the two horizontal curves to be improved. Since this scope would use the exis�ng horizontal alignment, the exis�ng side slopes would only need to be minimally altered to �e into the lowered ver�cal alignment. In addi�on the ditches would typically not be disturbed. Minimal to no disturbance of the slopes and ditches greatly reduces the �me needed for environmental clearances and permits and the acquisi�on of right of way. To further inves�gate the “pavement replacement” scope, District Construc�on staff met with local officials. They agreed that K-23 in Gove County could be closed while the en�re roadway surface was replaced. This would reduce the �me to complete construc�on and reduce traffic handling expenses. This op�on would take less �me to construct and would be less expensive than the “total reconstruc�on” scope. A�er comparing the alternate scopes, the “pavement replacement” scope was chosen for some of the following reasons. The exis�ng geometrics and roadside slopes were favorable to remain in place. The simple ac�on of pavement replacement along with lowering the profile would increase the shoulder width by approximately 2 ft. The “pavement replacement scope” would provide a safety improvement in less time and for approximately $7 million dollars less when compared to the “reconstruc�on” scope. Example 2: Constructability Issues An example of considering constructability issues when choosing a scope occurred on a K-7 reconstruc�on project in Johnson County. This sec�on of K-7 is a 4-lane divided highway carrying high traffic volumes in a densely urbanized area. This projec� ncludes the construc�on of an interchange that replaces the current at grade intersec�on at K-7 and Johnson Drive. I� s predicted tha� he exis�ng ground on the south side of the interchange will se�le due to the weight of the fill used to construc� he bridge embankments. It is an�cipated that 90% of this se�lement will occur in 11 months. Thus the construc�on of the bridges would be delayed 11 months unless another construc�on method could be u�lized. Three different scopes were considered.

81 The first op�on would construct all bridge abutments using piles and would involve an 11 month wai�ng period before construc�ng the bridges. Construc�on sequencing would include first construc�ng the bridge embankments. The bridge abutment work on the north side could begin without delay. The bridge abutment work on the south side would wait for the embankment to se�le for 11 months. A�er this timeframe, the piles could be driven into the embankments and the southern bridge abutments constructed. The next step would be construc�ng the bridges and the roadways on the southern bridge approaches. A�er comple�on, the project would open to traffic. This op�on would be the least expensive to construct but would take the longest and would incur delay related costs to KDOT such as paying twice for contactor mobiliza�on. The 11 month se�lement period would significantly Increase the amount o� ime that side road traffic is closed and movements from K-7 are restricted. In addi�on, the 11 month period with only minimal work being observed could create nega�ve percep�ons for the roadway users, area businesses and residents. The second op�on would use drilled sha�s to construc� he south bridge abutment and would avoid wai�ng 11 months before bridge construc�on could begin. The construc�on sequence would include construc�ng the bridge embankments followed by the abutments and then the bridges without delay. Se�lement would still occur in the south side embankment but with this op�on, the bridge could be constructed during this se�lement period. Due to the use of rigid pavement, paving the roadway on the southern bridge approaches could not occur un�l a�er the se�lement period. Being able to construct the bridge without delay greatly shortens or eliminates the delay to advancing to the next phase of construc�on. Although this op�on is more expensive than using piles for both abutments, it would incur less if any delay related costs, take less time to construct and would be an�cipated no� o create the negative percep�ons associated with the 11 month se�lement period. The third op�on would construct the bridges in the same manner as the second op�on but would avoid any delay in opening the roadway to traffic. To avoid the delay, this op�on would u�lize paving the southern approach o� he Northbound (NB) bridge with temporary asphalt pavement. The asphalt pavement on the approach could handle the se�lement with minimal distress. The NB bridge could then be opened without delay to two way traffic during the se�lement period. A�er the se�lement period, the southbound (SB) bridge approach could be paved with concrete and when ready, all traffic switched to the SB bridge. The temporary asphalt pavement on the NB bridge approach would be removed and replaced with concrete. Carrying traffic through construc�on during the se�lement period would provide the least delay to the traveling public but would require addi�onal traffic accommoda�on and pavement costs to KDOT. This op�on is the most expensive but would take the least time to construct.

82 A�er comparing the scopes, the op�on u�lizing the drilled sha�s without carrying traffic through the se�lement period was chosen. This op�on was the second most expensive, had the second shortest construc�on �meline, and li�le to no delay related expenses. Thus the foreseeable impact o� he delay in comple�ng a project for a facility carrying such high traffic volumes was considered to outweigh the addi�onal construc�on costs associated with Op�on 2. Example 3: Roadside Op�ons When developing alternate scopes, the width and type of shoulders, clear zone widths, and foreslopes should be evaluated. One example of evaluating these features was the bridge replacement project over the Big Blue River on US-77 in Marshall County. When evalua�ng the shoulder widths, the exis�ng shoulder widths in the area of considera�on and the current criteria were compared. The Big Blue River Bridge consists of two 12’ lanes and 1’ shoulders. In the vicinity close to the bridge, the exis�ng roadway consists o� wo 12’ lanes and 8’ composite shoulders. The exis�ng shoulders on other routes in the area are depicted on the KDOT Shoulder Map below. For this por�on of US-77, the current KDOT Shoulder Map suggests a 10’ shoulder width. The AASHTO Green book suggests an 8’ shoulder width.

83 Design Shoulder Widths Base d o n P rojected Traffi c – Ado pte d 4 /9 8 Legend : 4 ft. 6 ft. 8 f t. 10 ft . When e valuating the foresl op es, the e xisting conditions and the current c riteria were compared. I n the proj ect area, US-7 7 w as bui lt with 4: 1 f oreslopes. Current criteria suggest using foresl op es in the rang e o f 6: 1 t o 4 :1 . Pullin g all the se roadside options tog ether, several typical se ct ion scenarios wer e e valuated. Se e T yp ical Section table below. Typical Sect io ns Eva lu ated : Option Shoulder Widt h F oreslope Rat e C lear Zon e W id th Construction Cost A 10’ 6:1 30’ $8,670,00 0 B 10’ 4:1 34’ $8,340,00 0 C 8’ 6:1 30’ $8,350,00 0 D 8’ 4:1 34’ $7,930,00 0 Th e t ypical sectio n s el ected in cluded an 8’ composit e s houlde r w it h 4 :1 side slopes an d a 34 ’ clear zo ne. Th e p ropose d t ypical section mat ch es into th e e xistin g r oadw ay smoothl y a nd stays withi n c ur rent criteria ra nges. T hi s o ptio n c ould po tentially save approximately $740,00 0 i n roadwa y a nd bri dg e c osts .

84 Example 4: Traffic Handling and Accommoda�on On a project under development on US-36 in Norton County, traffic handling and accommoda�on played a par� n determining the project’s scope. A 4.5 mile sec�on of US-36 with 2 lanes, 10 foot composite (3’ asphalt pavement and 7’ turf) shoulders, and deteriora�ng pavement was selected for improvement. Current traffic counts are 3300 vehicles per day (AADT) with 21% trucks. Scopes considered for this project were “pavement replacement” and “pavement rehabilita�on.” In addi�on, when considering possible scopes for the project a typical sec�on with 10’ fully paved or composite shoulders and 4:1 or 6:1 foreslopes was evaluated. For the “pavement replacement” scope, the pavement recommenda�on is 11” asphalt surfacing. For the “pavement rehabilita�on” scope, the pavement recommenda�on is 4” of cold in place recycle (CIPR) with a 5” asphalt overlay. Regardless of scope, the exis�ng horizontal and ver�cal alignments meet current criteria and would not need to be modified. Since both scopes would replace or modify the exis�ng pavement, the supereleva�on could be improved where needed. When comparing construc�on costs, items such as earthwork, structure extensions, etc., were considered comparable since both scopes don’t adjus� he exis�ng alignment and would improve the foreslopes in a similar manner. Thus only the pavement costs were calculated and compared. This cost comparison es�mated that the “pavement rehabilita�on” scope is $1,800,000 less than the “pavement replacement” scope. Under the “pavement replacement” scope traffic on US-36 would be redirected on a state route detour with 20 miles adverse travel. A por�on of this detour would be on K-9. In the detour area, K-9 is a low volume highway with a 24’ roadway width with li�le to no shoulders. It would not be preferred to add the current traffic of US-36 (especially with 21% trucks) onto K-9. For the “pavement rehabilita�on” op�on, the traffic would be carried through construc�on. Due to the length of adverse travel and exis�ng roadway width of K-9, it would be preferred to carry these traffic volumes through construc�on. A typical section with 10’ fully paved or composite shoulders and 4:1 or 6:1 foreslopes were evaluated for both scopes. The use of 10’ wide shoulders would comply with current criteria but the use of composite shoulders would not comply with KDOT’s current shoulder policy. A 10’ composite shoulder would match the exis�ng shoulders on adjacent segments of US-36. For either scope, using composite shoulders could save approximately $1,060,000. The use of either 4:1 or 6:1 foreslopes would comply with current criteria. For either scope, the use of 4:1 foreslopes versus 6:1 foreslopes could save approximately $234,000. A summary of the poten�al savings in FY 2012 dollars is given below.

85 Poten�al Savings: Op�on Savings (FY 2012 dollars) Pavement Rehabilita�on vs. Pavement Replacement* $1,800,000 10’ Composite Shoulder vs. 10’ Fully Paved Shoulder $1,060,000 4:1 foreslopes vs. 6:1 foreslopes $234,000 *Does not consider life cycle costs. A�er evalua�ng the alterna�ves, the “pavement rehabilita�on” scope u�lizing a typical sec�on with 10’ composite shoulders and 6:1 foreslopes was chosen for some of the following reasons: • Es�mated ini�al construc�on cost savings of approximately $2,860,000 • Traffic can be carried through construction (preferred) • Exis�ng ver�cal and horizontal alignments comply with exis�ng criteria and can be le� in their present condi�on • The 10’ composite shoulder matches the exis�ng shoulders on adjacent segments of US- 36 • The 10’ shoulder width complies with exis�ng current criteria • Low cost ($234,000 for en�re project length) to improve from 4:1 to 6:1 foreslopes