ENGINEERING_CONSIDERATIONS_AND_INSTRUCTIONS_FOR_FIELD_PERSONNEL.pdf

ENGINEERING CONSIDERATIONS AND INSTRUCTIONS

FOR FIELD PERSONNEL

Dobbins ARB Drainage system.

Version 1.2 – Third Version

Date 11 July 2017

Revision History

Revision No.

Implemented By

Revision Date

Approved By

Approval Date

Description of Reason

1.0 M. Caspar 4/25/2017

1.1 M. Caspar 6/13/2017

1.2 M. Caspar 7/11/17

How to Use this Document:

This document contains project information such as contact information and specific design details.

In the design considerations section of this document, a narrative of the design is given for the construction personnel to understand what guided the Project Design Team during the design process. At the end of each discipline section are design considerations for the construction personnel. Each item of importance will be denoted by a check mark symbol.

In the Specification Considerations section, is a list of submittal items the specifications is requesting that is crucial to either ensure the design intent is met, or to ensure the contractor is conducting the proper coordination.

In the Utility and Permit information section, a list of the permits required by the contractor to obtain is listed.

In the Quality Assurance section of this document, a list of the required testing and reporting is given to ensure the correct preparation and materials are being used.

Lastly is the recommended site visits by the design team for consideration.

Attachment 3 FA6703-17-B-0003

Dobbins Airfield Storm Water System Phase 1 Certified Final Submittal Dobbins ARB FGWB-04-0014-P1

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Project Features and Summary Dobbins Air Reserve Base (DARB) is located in Marietta, GA and was built in 1943. The airfield was raised approximately fifty vertical feet when built and an existing stream was rerouted or piped to downstream outfalls. The main storm drainage systems have been in place for nearly 66 years. Over the years, DARB and Lockheed Martin (LM) have constructed new buildings, parking lots, and roads that have increased runoff to the storm drainage systems.

This project includes all work necessary to maintain the stormwater drainage systems west of

Taxiway 'J' on DARB. Areas where the slopes have failed or were disturbed from repair will be re-graded to obtain positive drainage and have sod applied to stabilize the soil. Work shall include all maintenance items identified in Drainage Basin II on the airfield.

In addition to the work associated with correcting the grade around the airfield, cleaning of existing flumes, pipes, and swales is required to reestablish proper drainage. New concrete flumes will be installed at various locations throughout the airfield to reestablish positive drainage and prevent future erosion and standing water.

Improvements to the existing storm pipe system will be facilitated through the installation of additional access manholes throughout the drainage system. Pipe cleaning and lining are a

2 | P a g e couple of the approaches proposed to improve the existing drainage system. In areas where pipe lining is not feasible, the system will be repaired through removal and replacement of existing pipes.

The final aspect of this project is the removal of trees on the north side of the runway to a distance of approximately 750 feet from the airfield centerline which is illustrated on the approved plans. This work will be completed in and around the State Water Buffer and

Jurisdictional Wetlands. No work will be allowed until all permits have been received.

This document describes the expectations outlined at the kick off, pre design, review and final review meetings.

a. Project Description

Project Title and Location: Dobbins Airfield Storm Water System Phase 1, Dobbins

ARB, GA

Project Number: FGWB 04-0014 P1

P2: 459023

i. Construction Site

The drainage system repair work is located in the airfield perimeter. The specific area of focus includes, the area directly west of Taxiway J to the western perimeter of the base. The scope of work includes: repairs and restoration of the existing drainage system and grading around the airfield. In addition to the drainage system and grading modifications, the project will restore flight line visibility from the airfield control tower by removing trees in the area north of the airfield.

ii. Economic Summary

This project has been funded in accordance with the approved 1391 dated 2 March 2012.

iii. Contract

DARB Civil Engineer will be responsible for bidding, contract administration, and construction services.

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Design Considerations I. Environmental Compliance

a. Applicable Codes and Criteria

Official Code of Cobb County, Part I, Chapter 50, Article 3 General

Official Code of Georgia, Title 12

Section 404 of the Clean Water Act (33 U.S.C. 1344)

b. General

On October 11, 2016, ecologists completed a delineation of Waters of the United States

(US) and Waters of the State within the proposed DARB Airfield Drainage Project area.

Resources observed in the project area include: one perennial stream; three intermittent streams; three wetlands; and one open water. The delineated resources generally match those identified in the previous Jurisdictional Determination.

These resources are considered Jurisdictional Waters of the U.S. and are regulated by

Section 404 of the Clean Water Act. The streams and open water are considered State

Waters, however only the open water and the southernmost section of the perennial stream are considered buffered state waters and all areas within 25-feet of these banks are considered State Regulated Buffers as described in Georgia’s Erosion and Sedimentation

Act.

A review of environmental permit requirements pertaining to the proposed project is provided below.

c. Cobb County Buffer Ordinance

The Official Code of Cobb County, Part I, Chapter 50, Article 3 – Land Disturbing

Activities establishes a 50-ft vegetated buffer immediately adjacent to buffered state waters within the county and depicted on the current county stream buffer map. Additionally, this ordinance requires a 25-foot impervious setback to be established from the edge of the 50-foot buffer. Non-exempt encroachments within these areas would require a variance from

Cobb County. The following resources are subject to the Cobb County Buffer Ordinance:

the non-armored section of S-12; and W-111. The project is anticipated to require a variance.

mailto:timothy.s.roscoe@usace.army.mil

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d. Georgia Department of Environmental Protection, State Buffer Program

The Official Code of Georgia, Title 12 (also known as the Erosion and Sedimentation Act of 1975), establishes a 25-foot buffer along the banks of all state waters, as measured horizontally from the point where vegetation has been wrested by normal stream flow or wave action. Non-exempt encroachments within the state-regulated buffer would require a variance from the Georgia Environmental Protection Division (GAEPD). The following resources are subject to the state-regulated buffer requirement: the non-armored section of

S-12; and W-111. The project is anticipated to require a variance.

e. Section 404, Clean Water Act

Section 404 of the Clean Water Act (33 U.S.C. 1344) regulates dredge and fill activities within Waters of the US. Each of the resources identified within the project area are subject to this regulation. Dredge or fill activities within the jurisdictional boundaries of any the resources would require permit authorization from the US Army Corps of Engineers

(USACE). Activities that will result in the loss of, or permanent adverse effect to Waters of the US may require compensatory mitigation.

f. Summary and Conclusion

As currently proposed, the project is anticipated to require a Cobb County Buffer Variance, GAEPD Buffer Variance, and a Section 404 Nationwide Permit from the USACE. In terms of schedule, stream buffer variances are typically authorized in three to four months while a Section 404 Nationwide Permit application is typically authorized within three months.

Work within the Waters of the US or the county- and state-regulated buffers, may not commence until the Section 404 permit and the buffer variances are authorized.

g. Design Consideration

� All permits must be in place prior to the start of construction.

� The contractor is responsible for confirming all disturbed areas are stabilized in accordance for with the erosion control plans.

� The state of Georgia requires that a Level 1A Certified person be on site during all land disturbing activities.

� Contractore is required to file a NOI with the GAEPD and pay all fees prior to the start of construction.

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II. Erosion and Sediment Control

a. Applicable Codes and Criteria

Erosion and Sedimentation (E&S) Act of 1975 (O.C.G.A. 12-7-1 et. seq.)

National Pollutant Discharge Elimination System (NPDES) Permit for Infrastructure

Construction Projects

Georgia Water Quality Act

Georgia Rules and Regulations for Water Quality Control Chapter 391-3-6

Section 404 of the Clean Water Act (33 U.S.C. 1344)

b. General

The proposed erosion control measures for the construction of the facility will be in accordance with the 2016 Edition of the State of Georgia Erosion Control Manual and will consist of silt fencing, inlet protection, sediment storage practices, and stabilization measures. Erosion and Sedimentation Control Plans will be submitted to the base for approval and submittal to the Local Issuing Authority.

c. Site work

Gabion baskets will be used to stabilize the stream bank of the perennial stream as the flow exits the pipe system under the airfield and feeds into Big Lake. This system will prevent the erosion of the stream bank during major storm events. In addition these baskets will act as a deterrent to water fowl in the area.

Any soil disturbance in the area will be stabilized with sod that meets the vegetative specifications of the base. No vegetation that is commonly a food source to fowl in the area will be used in the plantings. Types of vegetation that will not be used include millet or other grain-producing vegetation.

d. Schedule

The project work will take place almost entirely within the airfield perimeter. Special precautions will be taken to limit the effects of construction on base operations. Any proposed closure to the airfield will be coordinated not less than 30 days prior to the scheduled work. At no time shall the airfield be closed for a period longer than 4 days.

Security of the site is critical. As such security forces will be notified not less than 2 weeks prior to the relocation of any perimeter fencing so precautions can be taken to control the perimeter during the construction.

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Foreign Object and Debris (FOD) Control will be critical during this project. As such FOD checks will be part of the daily task plan. In addition daily site clean-up will be critical in allowing base operations to continue throughout the project.

A known schedule conflict is the base air show on 24 and 25 March 2018. The site area will be stabilized and all equipment is expected to be removed from the airfield from 21

March 2018 through 26 March 2018.

e. Design Consideration

� The contractor is responsible for confirming all disturbed areas are stabilized in accordance for with the erosion control plans.

� The state of Georgia requires that a Level 1A Certified person be on site during all land disturbing activities.

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III. Civil

a. Applicable Codes

UFC 3-201-01 Civil Engineering

UFC 3-220-01 Geotechnical Engineering

UFC 3-220-04FA Backfill for Subsurface Structures

UFC 3-250-01 Pavement Design for Roads and Parking Areas

UFC 3-250-03 Standard Practice Manual for Flexible Pavements

UFC 3-250-04 Standard Practice for Concrete Pavements

UFC 3-260-02 Pavement Design for Airfields

UFC 4‐022‐1 Security Engineering: Entry Control Facilities/Access Control Points

UFC 4-022-03 Security Fences and Gates

AASHTO American Association of State Highway and Transportation Officials

EPA Environmental Protection Agency

Standard Specifications for Construction of Transportation Systems by the Georgia Department of Transportation, 2013 edition

b. General

The purpose of this project is to maintain and repair the existing stormwater infrastructure west of Taxiway J on the DARB property. This has been done by providing cleaning of debris and blockages from the existing infrastructure by the use of a jet truck. Immediately following the cleaning of each segment, a video inspection of the line was performed to determine the condition of the stormwater system along with the location of damages and failures within the system. The video data was evaluated in order to identify needed repairs to the existing storm drainage infrastructure. The objective is to minimize pipe separations, any undermining of outlet structures, infiltration, and erosion by the least invasive methods and to identify manholes which have been covered during previous projects where the grade around the airfield was augmented. In addition to infrastructure repair, the project will define grading contour modifications to minimize standing water problems identified by the DARB on the runway, taxiways, or impoundments in the infield that may be hazard to aircraft or attract birds.

The limits of construction for the drainage improvements is bound on the east by Taxiway J and continues to the western property line of the DARB. The analysis consists of hydrologic and hydraulic modeling the existing storm water drainage system and providing recommendations for measures that will improve the flow through the system with in these limits.

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The plans represent a merger of survey data, DARB provided GIS data which include grades and utility locations, and LM provided supplemental underground utility information. In addition to the merged documents, the contractor shall be required to obtain the services of a private utility locating company to verify the location of all underground utilities prior to construction.

The drainage system for DARB was initially designed to accommodate the configuration of the base in 1942. The original base configuration consisted of Runway 11/29 at a length of approximately 5,825 feet. The runway was expanded to the west in the 1950s to accommodate the requirements of larger aircraft designed by LM for use by the Air Force.

The current runway length is approximately 10,000 feet. The current drainage system was designed to accommodate the expansion of the runway and adjacent taxiways during the 1950s runway modifications. The drainage system allows the storm water to travel from the western edge of the base through a series of culverts and flumes into a dual run of 48-inch pipes. The system conveys water east to Taxiway J where the pipe directs water north under Runway 11/29 and outfalls into the pond north of the runway. The double 48” pipes become 54” pipes just south of the runway, this size is maintained to the outfall. There are

Figure IIB-1: Existing Drainage System

Outfall

9 | P a g e several pipe networks that connect to the main run of double pipes. These collect the storm water from smaller drainage areas.

Once construction documents are completed for this project the USACE will turn them over to the base Civil Engineering Unit. From completion of documents, the base will coordinate and handle the contracting and construction administration for this project.

c. Existing Condition Survey

A video survey inspection was performed of the existing drainage system. The results of the survey show some damage in different locations throughout the system. The damage to existing pipes include degradation over time causing failures in the pipe structures, separation of the pipe culverts at the joints, and the installation of utility conduits boring through the culverts.

Several pipe systems could not be videoed due to debris blocking the equipment and/or the lack of access to the pipe networks to allow the video camera to reach the entire lengths of the system. In most cases, the video was able to confirm the pipe diameter both upstream and downstream of the blockages. The information found for these areas was assumed to be consistent between locations. However, due to limited amount of information for the drainage systems, assumptions were made during the modeling analyses. Assumptions include: pipes are the same material as that of the adjacent pipes; the pipes without information flow without restrictions or damage; and if access for video equipment was restricted, the pipe diameters were assumed to be consistent with the adjacent pipes.

d. Existing Conditions Drainage Evaluation

The drainage evaluation was performed using the Autodesk Storm and Sanitary Analysis 2016 application. The existing storm water drainage system contains 41 subcatchments ranging from 0.22 acres to 82.19 acres with a total drainage area of 456 Acres. While the total acreage of the 2011 analysis of Drainage Basin II is consistent with this evaluation, the subcatchment delineation differs slightly.

There are drainage structures and piping in the northeast corner of Drainage Basin II which flow eastward, to an intermediate detention pond north of the “AF REFUELER VEHICLE PARKING”, which then outlets to the east, through a wooded area, and eventually to the north side of Big Lake. This area is included in Drainage Basin II due to the outfall at Big Lake, however because of the flow path, this subcatchment is not included in the 2011 analysis or this drainage evaluation.

The existing storm water system was modeled for Drainage Basin II using the TR-55 Method per the UFC design criteria. UFC 3-201-1 paragraph 3-9.1 states:

Ponding is not allowed on taxiway and runway pavements including paved shoulders. Ponding around apron inlets must not exceed 4 inches (100 mm). Center 50 percent of runways; center 50 percent of taxiways serving these runways; and helipad surfaces along the

10 | P a g e centerline must be free from ponding resulting from storms of a 10-year frequency.

Compliance with UFC 3-201-1 paragraph 3-9.1 is intended, however due to the rehabilitation limitations of this project, full compliance within Drainage Basin II will not be achieved, however improvements to the existing conditions will be accomplished with this scope of work.

The Time of Concentration for the system ranges from 5 minutes minimum to 20 minute maximum. The TR-55 Curve numbers range from 61 for open space grass cover greater than 75%, hydrologic soil group B to 98 for impervious areas per the Georgia Stormwater Management Manual Volume II. The weighted Curve Number for the entire modeled drainage area is 85.

Several assumptions were required when analyzing the system due to the lack of video in portions of the storm water network and include the following:

• Manning’s Roughness Values o RCP, Poor Joints, Rough Walls = 0.017 o CMP = 0.024 o Channels = 0.013 – 0.032

• Parallel pipe transitions from 48-inch RCP to 54-inch CMP at Combined JB II- 200 / 300

• Increased manning’s roughness to 0.025 to represent debris/blockage within pipe noted by survey (utility or TV)

• Where possible, specific inlet grates are selected in the model to best represent grate type, open area and wetted perimeter. All other inlets are modeled as FHWA HEC-22 Generic Rectangular drop inlets with the appropriate grate length and width either on grade or on a sag

• Ponding areas were established using 1 foot contour data for inlets on sag.

• Headwalls are modeled as storage nodes with depth area curves to produce available volume based on 1 foot contour data

• Junctions o Junctions boxes are modeled as storage nodes with a constant area per depth to produce the available volume o Buried or no access junctions and manholes are modeled with a max surcharge elevation which prevents flow from leaving the system

• Outfalls are modeled with a normal boundary condition (Tailwater from pond is not currently being modeled).

The AE performed modeling of the system for a 2 year, 10 year and 25 year – 24 hour storm events. The analysis resulted in a surcharge within the pipe network and ponding of water at some inlets and headwalls. Inlet GI-II-705 near Taxiway L and the maintenance area pad is overwhelmed with surface runoff and restricted by lack of downstream capacity near the electrical vault and therefore experiences flooding. The model indicates that the flooding at inlet GI-II-705 encroaches the shoulder of Taxiway L during the 10 year event

11 | P a g e and the Taxiway L pavement during a 25 year event. The modeling confirmed that most of the existing ponding that occurs at the inlets and headwalls does not reach the taxiway or runway pavements. Therefore the pavement ponding appears to be isolated to the areas where vegetation has become overgrown causing water to back onto the airfield and not by the drainage system itself. The existing ponding will be corrected with grading modifications. There is a known ponding issue at the electrical vault, located at the intersection of 7th Street and the maintenance road, south of the overrun area and outside of the airfield security fencing. The model confirmed this ponding, which is caused by a drainage system restriction across the maintenance road. A proposed 3’ x 5’ double box culvert in this location should eliminate the ponding in the area near the electrical vault and reduce the extent of the flooding that occurs upstream at inlet GI-II-705 so that the extent of the flooding no longer reaches Taxiway L pavement during a 10 or 25 year event.

e. Storm Water Management

The existing system contains corrugated metal pipe (CMP) that is in need of repair, based upon the video inspection. The AE investigated two types of methods to line the existing CMP within the drainage system. One method is to install a cured in place polyurethane (CIPP) liner. This method requires inserting a liner in the pipe and then forcing steam through the length of the pipe to expand and cure the polyurethane pipe in place. In order to effectively perform the method, access along the pipe network has to readily available.

With airfield closures limited to a maximum of 4 days and restriction on the contractor’s equipment within the airfield, the use of this process is not feasible. Due to equipment limitations, the CIPP method would also require an increase in the number of new drainage structures constructed. The addition of the polyurethane liner reduces the working volume of the CMP, thus reducing the hydraulic capacity of the stormwater system. During construction, the existing flow through the pipe being lined will need to be diverted around the area of work through a temporary bypass system.

The other method is to apply centrifugal spray concrete to the inside of the CMP pipe. The concrete can be applied by a machine for smaller diameter pipes or manually by human access for larger diameter pipes. With the potential for human access in the large diameter pipes, all OSHA requirements for confined space entry must be strictly adhered to. The concrete will be applied with a thickness that will eliminate the interior corrugation that exist in CMP pipes. By eliminating the corrugation, the Manning’s value for the pipe is reduced, increasing the effectiveness of the storm drainage system. This method also, requires the existing flow through the pipe being lined to be temporarily diverted around the area of work during the construction process. The spraying process will be utilized to repair separated joints from the interior of pipes. The concrete provides additional structural integrity to the existing pipe. After coordination with DARB personnel, it was determined that the centrifugal spray concrete method would be the most effective and least intrusive method to help improve the existing drainage system without having to replacing the entire system.

A hydraulic analysis of the system with the centrifugal spray concrete revealed that the surcharging was still evident in the main double 48-inch and 54-inch pipes. The system is functioning in the manner it was designed while demonstrating the surcharge. There is no

12 | P a g e evidence of flooding within the airfield and thus it was determined to maintain the current drainage system design and only add features to the system that assist in the general maintenance and upkeep of the current system.

The addition of drop inlets at strategic locations in the system will assists in general maintenance and upkeep of the system. Inlets are to be installed where access to the system is limited. Currently there are buried junction boxes that are being used at change direction of the pipe, it is proposed to replace the existing junction boxes in their entirety with new inlets. These inlets will provide the base operations and maintenance proper access to the drainage network in order to keep the systems free of debris and sediment.

In adding to the pipe lining and new inlets, new pipes will be install under Taxiway M and Taxiway L. A new pipe is required under Taxiway M for two reasons. The first is the entry headwall into the system currently requires a waiver. The desire is to replace the headwall with a drop inlet, thereby, eliminate the need for a waiver. This could be completed by lowering the drainage system. The other reason is that there is an existing fiber optic line within the pipe segment. As such, it will be abandoned in place and filled with flowable fill to prevent future settling underneath the taxiway.

The second pipe replacement is under Taxiway L. The current system is submerged and the downstream edge is below grade. The proposed pipe replacement will keep the pipe from being submerged.

f. Demolition

The demolition associated with the drainage improvements include open trenches cut through Taxiways L and M for the installation of proposed storm water pipes, and the demolition and removal of underground junction boxes in order to install new inlets and junction boxes.

Grading in certain areas within the project limits will be required to establish positive drainage flow. The existing sod and topsoil will be removed within a 10-foot wide area along the shoulders of the runway and taxiways and along the edge of pavement of the maintenance access roads as indicated on the construction plan sheets.

g. Pavement Design

The pavements selected for this project are concrete and asphalt paving. The intent is to replace the paving only in areas impacted by construction of the proposed drainage system improvements. The existing pavement has no known settlement issues over the existing stormwater infrastructure.

Concrete Paving: Concrete paving will be utilized in the areas of Taxiways L and M where the proposed drainage improvements are to occur, as well as, to reconstructed areas of the maintenance roads. The proposed sections are to match the existing pavement sections of the taxiways. Based on the pavement evaluation provided by the base, these sections are 16-inches in depth. However, the contractor is to field verify the existing pavement section

13 | P a g e before installing the proposed pavement section. The pavement shall be placed in accordance to the construction design plans and the UFC 3-260-02.

Asphalt Paving: Asphalt paving will be utilized for the paving of the shoulders along Taxiway Land M where the proposed drainage improvements are to. The pavement design shall match the existing pavement. The contractor will be responsible for field verifying the existing pavement design. The pavement shall be placed in accordance to the construction design plans and the UFC 3-260-02.

h. Pavement Thickness Design

The DARB existing runway is classified as type B based upon its capacity to accommodate a C-130 which is the most commonly used aircraft at DARB. This classification is also based on its potential to accommodate C-5 and C-17 aircrafts per UFC 3-260-1 Table 3.1.

The existing pavement sections consists of a 16 inch Portland Cement Concrete (PCC) layer over a variable depth separation or engineered fill layer. The design of the replacement PCC section follows with UFC 3-260-02 Pavement Design for Airfields.

1. Traffic Per UFC 3-260-02 Chapter 3 Section 1.a, bases such as Dobbins should be designed as medium airfield type. The lifetime pass criteria for the airfield as defined in the UFC consists of the following.

Aircraft Weight, lb Passes

Type A Traffic

Type C Traffic

F-15E 81,000 60,750 100,000

C-17 580,000 435,000 400,000

B-52 400,000 300,000 400

For lesser used portions of the airfield such as the hangar apron at the end of Taxiway L light airfield type aircraft will be used for evaluation. This seldom used apron once held Navy F-18 aircraft. The light airfield traffic pattern is as follows:

Aircraft Weight, lb Passes

Type A Traffic

Type C Traffic

F-15C 68,000 51,000 400,000

C-17 585,000 438750 400

2. Frost The climate at DARB has a Mean Annual Temperature of 61.4°F and an Air Freezing Index of 50 for a 50 day freezing season. This limited frost season and the limited frost penetration per UFC 3-301-01 is taken into account in the pavement design and is determined not to pose an impact to the pavement structure.

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3. Existing Subgrade The existing subgrade at DARB largely consists of stabilized and compacted clay type soils. Specifically, Pacolet soils (SC/SM =Silty / Clayey Sands)beneath the majority of the runway. The UFC recommends in absence of other information a K value of 50-250 psi/in should be used. The selected k value will be 150psi/in.

Historical structural testing performed by AFCESA and issued in a draft report in March of 2013 on the existing pavements at DARB has been requested. The report breaks down CBR / K value by pavement area and layer.

4. Crushed Aggregate Base

The replacement section for medium airfield usage will consist of 10 inch of graded crushed aggregate base course to provide a structural base for the pavement section. This section was determined through PCASE using a 16 inch Portland Cement Concrete Pavement section to match the existing section of taxiway M.

For lesser used portions of the airfield such as Taxiway L using the existing pavement section of 11.25 inches the resultant graded aggregate base course section is 6 inches for Traffic Area C, Air Force Light design.

6. Drainage layer There is no known drainage layer existing so this a drainage layer will be omitted as part of the proposed repair section.

7. Resultant PCC Sections The existing Portland Cement Concrete Pavement sections were used per the report provided by DARB and included in Appendix G. The aggregate base layers were adjusted to make the existing pavement sections work.

i. Pavement Construction Materials

This section discusses the properties required for the materials to build the runway.

Included are concrete, hot mix asphalt (HMA), drainage layer, stabilized bases, and crushed aggregate bases.

1. Rigid Pavement.

The design flexural strength of the Portland cement concrete is 650 psi at 14 days.

Regional material sources are readily available with several quarries being located in or near the Atlanta area. The 16 inch PCC pavement section will generally use 25 foot by 25 foot joint spacing to match existing pavement. Longitudinal and transverse construction joints will use 1 inch diameter dowel bars 20 inches long at 18 inch spacing.

The 11.25 inch PCC pavement section will use 12.5 foot by 15 foot joint spacing.

The Longitudinal and transverse construction joints will use 1 inch diameter dowel bars 16 inches long spaced 12 inches apart. The transverse contraction joints will be sawcut and rely on aggregate interlock for load transfer. All construction and

15 | P a g e contraction joints will be sealed with field poured silicon joint sealant. Expansion joints will be ¾ inch minimum and sealed with field poured silicon joint sealant.

The asphalt / concrete shoulder joint will be a ½” field poured joint with backer road and silicone joint sealant.

2. Flexible Pavement Hot Mixed Asphalt (HMA) will be utilized for the paved overrun and shoulders on the airfield. The section will be 2” thick on a minimum 8” stabilized section. The contractor will have the option of submitting GDOT mixes for consideration in lieu of a traditional job mix formula (JMF) for the surface course.

3. Base Courses

1) The crushed aggregate base course layer will be constructed of fresh quarried crushed aggregate.

j. Grading

There are several areas of the site in which standing water occurs in low lying areas. These areas will be re-graded to obtain positive drainage. In many cases, standing water occurs along the shoulder of pavement due to sediment build up over the years. These areas will be lower and graded to ensure positive drainage away from the pavement surfaces and into inlets. Longitudinal and transverse grade changes within the runway clear zones will be as gradual as practical and abrupt changes or sudden reversals will be avoided, in accordance with UFC 03-260-01 Table 3-2. All areas will be stabilized using rolled sod that is pined to the ground to prevent disturbance and damage to aircraft in the area.

k. Erosion Control

The proposed erosion control measures for the construction of the proposed drainage system improvements will be in accordance with the State of Georgia Erosion Control Manual and will consist of silt fencing, inlet protection, and outlet protection and stabilization measures. Erosion and Sedimentation Control Plans will be submitted to the base and the Local Issuing Authority for approval. Erosion control within 300 feet of the airfield shall be selected as to reduce the potential of FOD.

l. Utilities

The contractor will be responsible to locate all utilities within areas of disturbances. The contractor will also be responsible for any damages done to the utilities during the course of this work.

The utilities along Taxiways L and M shall be located by hand in order to prevent damages to the utilities during the construction of the proposed storm water drainage pipe.

m. Landscaping

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Other than sod, no landscaping will be included in this project. Sod will be required for all disturbed areas in accordance with the DARB turf establishment requirements.

m. Design Considerations

� A geotechnical engineer should be retained by the contractor to evaluation subgrade compaction and to collect concrete break samples.

� For pipe lining activities the following should be considered.

� For the pipe crossing taxiway m getotechnical data showed the potential for rock at depth.

Rock may be incountered in this area.

� MATERIAL VALIDATION. Values reported in Technical Data Sheets should have recent test reports conducted to ASTM Standards within the past two years from independent, certified testing laboratories which confirm the values as reported. These validations should be made using samples of the material applied as it will be in the field so that the values stated will more closely match those achieved by the contractor in the field. There should also be qualifications based testing geared towards assessing the installed liner's in-place performance which should include long-term testing done to determine any variations to these values that will occur over time under load. This material's engineering is essential to establishing the valid engineering properties to be used in the structural engineering of the liner.

� THIXOTROPY. The concrete mix must possess the ability to become fluid (or experience a significant decrease in viscosity) when energy is applied (i.e. mixing, pumping) to enable pumping distances up to 500 feet without separating; and, once cast into place on the wall of the host pipe, it must quickly revert to its initial viscosity to provide sufficient adhesion to build onto to the crown and walls of the host pipe.

� WATER CONTROL. Changes from prescribed volumes (i.e. the water-cement ratio) can make a big difference to the materials finished properties so amounts must be closely controlled. Processes that employ dry mixes must have controls in place that regulate the water introduced downstream to eliminate the opportunity of human error.

� FIELD PLACEMENT. The material and its application method to the pipe must provide sufficient void filling, densification, and adhesion. The impact velocity of the concrete against the prepared pipe surface along with alternating the direction of the spinning head is the best way to ensure consistently high quality. There should be little or no rebounding of material. The proper impact velocity range should be empirically derived and the relationship found committed to a solution that is computer calculated to operate at the best speed for uniform compaction for the numerous diameters and shapes of the host pipe.

� CRACKS. Concrete is rigid and can be prone to cracking as a result of movement from settlement or dynamic loading. Common engineering practice is to limit the acceptable

17 | P a g e crack width to 0.0625” to protect against soil penetration and/or formation of shards and to 0.010” crack width to prevent water penetration (approximately ½ the thickness of a credit card). Although such cracks are small, without further treatment, they get worse. Materials should have the ability to repeatedly “heal” such cracks after they develop to prevent leaks and long- term structural damage.

� FLEXURAL TOUGHNESS. Rigid concrete liners are very strong in compression and can withstand soil and hydrostatic loading independent of the host pipe. Most concrete mixes are not designed to be very strong in tension. However, the engineer should be advised that the new generation of concrete liners are capable of being designed to demonstrate a degree of ductility which, in turn, produces flexural toughness

(the ability to absorb energy up to fracture). This value is measured by ASTM C293.

Modulus of Rupture Values should be 1,500 psi or higher.

� EXPERIENCE is a necessary prerequisite because it immediately impacts the quality of the installed lining. Inexperience makes for disastrous results. Because the properties of the installed liner are critical, both materials and the installation system should be from a single source with a proven success record of at least ten(10) years. Time is the best judge of performance.

� COLD JOINTS. Materials should have exceptionally high bonding strengths that allows additional layers to be applied with as much as three (3) days between applications without fear of creating cold joints that can lead to separation, dis-bonding or delamination. Demonstration of this should be a part of any manufacturer's material validation process.

� MULTIPLE COMPACTED LAYERS. Just as soil is placed in thin lifts for a denser level of compaction under highways, multiple layers in the placement of the liner can create a more densely compacted liner. Single pass applications at thickness greater than 0.5 inch can cause minute amounts of sagging that takes away from the densification of the application process and may entrap air that produces voids in the liner.

Such voids typically can go undetected during the acceptance inspection only to manifest as a failure later on.

� FILLED CORRUGATIONS. The most practical and reliable way of delivering the designed minimum wall thickness is to make the basis for the wall thickness the crests of the corrugations, as required by ASTM A979, so that all valleys are completely filled because:

o Attempting to follow the corrugations result in uneven material application that is heavy on one side and thin on the other side of each corrugation; (see diagrams below) o Flows through the pipe are improved by a uniform inside dimension eliminating restrictive turbulence

18 | P a g e and impediments that retain soil and debris.

o Visual verification of the thickness by the inspector is much easier.

o Minimum coverage over protruding bolts prevent concentrated areas for stress cracks.

Asymmetrical Lining Fully Filled Lining

� IMPROVED FLOW. The uniform inside dimension should permit unobstructed flows that precludes debris settlement and minimizes damage from abrasion.

� MAXIMIZE PIPE CAPACITY. Centrifugally compacted lining must have the physical values that provide full structural reinforcement and sealing without restriction or loss of pipe capacity. Uniform inside diameters provide better flow characteristics than the original pipe's corrugations and sliplining typically results in 35-

45% reduction in capacity.

� IMPERMEABILITY. Leaks are the enemy of pipe because soils wash in with the ground water creating voids around the pipe exterior and sink holes during settlement.

Moisture trapped in the concrete will expand and spall during freeze/thaw cycles. Voids allow water and air around metal pipe contributing to external corrosion. Concrete liners with very high density (<50 Coulombs) prevent water from migrating through capillaries and microfractures. The industry uses ASTM C1202 to measure its resistance to water penetration.

� ENGINEERING. The thickness design should be based upon proven soil-pipe interaction for the specific liner material that is specified. The design should be stamped by a registered professional engineer.

� CORROSION PROTECTION. The liner material should contain rust inhibitors when covering corrugated steel culverts in storm water applications. In sanitary sewers, it should provide MIC prevention.

� ENVIRONMENTALLY SAFE. The liner material should not contain industrial waste products that may leech into waterways either before, during or after curing. ASTM

A979 limits the amount of fly ash that is permitted. Liners using styrene are not allowed.