WEF Collection Systems Conference 2017

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1 NOT IN MY BACKYARD, ANYMORE: A SUCCESSFUL BACKYARD SEWER REPLACEMENT PROGRAM Authors: Richard E. Underhill, P.E., PACP, Greeley and Hansen; Kelvin Coles, P.E., ENV SP, Greeley and Hansen, Belinda Wilson, Virginia Beach Department of Public Utilities ABSTRACT Purpose To present the process of designing and constructing a successful backyard sewer replacement project in a well-established, older neighborhood. To discuss the obstacles, challenges, and public concerns that needed to be addressed to obtain homeowner buy-in of the project and to provide a safe construction environment. Benefits The paper will share lessons learned in the design and construction phases of the project and provide suggestions to others on how to gain project acceptance from multiple stakeholders. Status of Completion The construction project is in progress and will be substantially complete by the date of the conference. Narrative Backyard sewers are common in many older sewers in American cities. The sewers in many residential subdivisions built in the 1950s were installed in the backyards of residences, along property lines or easements, because it was easier to put them there than in the street. Thus avoiding construction traffic disruption as new houses were built. In many older neighborhoods that originally had septic tanks and drain fields, it was easier to connect the lateral in the back of the house to a backyard sewer. This all seemed like a good approach back in the day. But, as any Collections System Operations and Maintenance supervisor will tell you, back yard sewers are difficult to maintain. Eliminating back yard sewers often involves constructing a new main line sewer in the street in front of the house and routing the sewer lateral around the house, from the back to the front. To do this, the designer must resolve many issues. Over the years home owners make improvements to their properties such as constructing fences, sheds, and other structures in the their back yards and by planting trees and shrubs along the property line. These amenities inhibit maintenance crew access and make manholes and cleanouts hard to find. Older sewers that were poorly constructed and have open, leaky joints contribute to higher wet weather flows due to infiltration and inflow (I/I). Open joints can also contribute to root intrusion and cave-ins due to soil migration, both of which can cause sewer blockages. Poor access makes clearing blockages with conventional truck mounted equipment difficult if not impossible. Sewer access problems, homeowner complaints, and the need for I/I reduction drove the City s decision to eliminate the back yard sewers in the project area. 557

2 Homeowners also make improvements to their property that inhibit routing new laterals around the house, such as garden and flowerbed hardscapes, ornamental structures, privacy fences, decks, driveway and sidewalk extensions, and trees and shrubs. In the project area, all of these things had occurred over the years, and the property owners took pride in how their yards looked. The neighborhood had been constructed in the mid 1950 s in a previously wooded area that contained many large white oak trees, some with diameters of 4 or more feet, hence the name of the neighborhood, White Oak. Because of the age of the neighborhood many trees that were planted years ago were also big and well dispersed about the properties. Another consideration in design of the new house laterals is the minimum slope required by the local building code, usually about 1%. This can become an issue at the end of the main line sewer where it is shallower and long lateral runs may be necessary. Maintaining vehicular and pedestrian access to properties during construction is an absolute requirement. Traffic control plans can become extensive and require several phases to construct the project. Our approach to addressing the project constraints and considerations discussed above included: Inspecting and photographing properties to document the existence of features that could impact lateral re-routing. Having discussions with property owners during the field inspections to hear their concerns. Sending maps of the proposed lateral re-routing to each property owner with a form requesting their acceptance and any information on abandoned septic tanks or underground fuel oil tanks. Conducting a public meeting at a nearby venue to describe the project and to get feedback from property owners. The project is currently under construction, with few complaints, and will be completed in the next several months. KEYWORDS Backyard Sewers, Public Participation, Mitigation INTRODUCTION Overview The City of Virginia Beach, Virginia is located in southeastern Virginia in the part of the state referred to as Hampton Roads. The city is bounded by the Chesapeake Bay to the north, the Atlantic Ocean to the east, North Carolina to the south, and the Cities of Norfolk and Chesapeake to the west. The city is one of the largest in Virginia with a total area of 1,287 square kilometers (497 square miles) and an estimated current population of about 456,000 people, which is about 27% of the total population in the Hampton Roads metropolitan area (1.7 million). The city is a thriving resort area with 59.5 kilometers (37 miles) of beaches, and includes three major 558

3 Department of Defense bases. Visitors to the city almost equal the resident population, averaging about 450,000 per month. Virginia Beach Location 559

4 Virginia Beach Oceanfront The City s sewage collection system consists of about 1,947 kilometers (1,210 miles) of gravity sewers ranging size from centimeters (4 inches) to centimeters (36 inches). The area is relatively flat; therefore, sewer run lengths away from a central sewage pump station are limited by the practical depth of the pump stations and the need to maintain minimum sewer slopes. As a consequence, there are about 405 sewer basins in the city, each served by a sewage pump station. 560

5 Project Area The project presented in this paper is located in the White Oak neighborhood, which is served by Virginia Beach Sewer Basin pump station 417. A map of the sewer basin is shown to the right. White Oak is a relatively older neighborhood in the city, with the majority of the 50 residential structures built in the early 1950 s. There are many large white oak trees scattered through the neighborhood which is probably how it got its name. Over the years, the various homeowners have made improvements to their property including hard and vegetative landscaping, drive way extensions, fences, gardens, walkways, decks and building additions. For the most part, the home owners take pride in the appearance of their properties which results in an overall attractive looking neighborhood. Some photographs of the neighborhood before the construction project are shown below. Project Area Location 561

6 White Oak Drive (New Pavement Overlay) White Oak Drive (Large Trees) Englewood Drive (Landscaping) 562

7 Wellston Court (Landscaping) Gravity Sewer System The original homes were served by on-site septic tank / drain field systems, which were abandoned when a developer installed a vitrified clay pipe and cast iron pipe gravity collection system in the mid 1950 s. The developer installed most of the main line sewers along the back property lines of the residences, with one connecting sewer located in a city street right of way. This was done because it was easier to connect to the house sewers formerly going to septic tanks in the back yards and it avoided disruption to existing streets and traffic access. Homes built after 1955 were connected directly to the new sewers. This seemed to be a good idea at the time, but has become a problem for maintenance sixty years down the road. Fences, sheds and other amenities constructed by the homeowners along the back of their lots and trees and shrubs that have been planted or have emerged over the years have made access to the backyard sewers practically impossible. The photos below show some of the existing conditions along the backyard sewer routes. Backyard Sewer Along Fence Line 563

8 Backyard Sewer (Fences and Trees) Side Yard Sewer (Trees and Fences) The tables below present the characteristics of the existing collection system. Sanitary Sewer Collection System Summary Category Characteristic Installation Year 1955 Gravity Main (LF) 3,858 No. of Manholes 13 No. of Public Main Line Cleanouts 7 No. of Laterals

9 Gravity Main Characteristics Material Diameter 6 (LF) 8 (LF) 10 (LF) Total (LF) Clay 1,167 1, ,059 Iron Total 1,167 2, ,858 The figure below shows the locations of the existing mainline sewers in the neighborhood. White Oak Neighborhood Backyard Sewer System 565

10 The sewershed that the White Oak neighborhood is part of was designated as a Sanitary Sewer Evaluation Study (SSES) basin based on field investigations and flow monitoring by the City. The results of SSES field investigations that were conducted in the White Oak neighborhood are shown in the figure below. Based on CCTV inspection, many of the existing sewer segments had a NASSCO PACP grade of 4 or 5 (based on the quick score method). The existing sewer conditions are shown in the figure below, which shows the sewer segments with a PACP grade of 4 or 5 as red lines. The poor sewer conditions and a history of service calls for blocked house sewers further justified the sewer replacement project. Replacing the old clay sewers with new PVC sewer pipes will reduce infiltration and inflow from the project area. Existing Sewer Conditions 566

11 Four alternative sewer alignments were considered, ranging from no action to replacement of all gravity sewers. The selected alternative was replacement of the sewer system at a new tie-in location. The new 954 m (3,130 linear foot) neighborhood sewer system consists of 20.32, 25.40, and cm (8, 10 and 12 inch) PVC pipe. The new sewer system is shown below. New Gravity Sewer System 567

12 Water System The homes in the White Oak neighborhood were originally served by individual water wells. Cast iron water mains ranging in size from to cm (4 to 6 inches) were installed in The characteristics of the water distribution system which existed prior to this project are presented in the tables below. Water Distribution System Characteristics Category Characteristic Installation Year 1972 Water Main (LF) 3,013 No. of Service Lines 50 No. of Water Meters 50 No. of Fire Hydrants 3 No. of Isolation Valves 12 Water Main Characteristics Diameter Material 4 (LF) 6 (LF) Total (LF) Cast Iron 691 2,332 3,013 The City s water distribution system model and hydrant tests were used to check the fire flow adequacy of the existing looped system and it was determined to be inadequate due to high pipe velocities (>11 fps). This and the age and material of the pipe drove the decision to replace the water mains with a new looped system as part of the sewer replacement project. The original and new water distribution systems are shown in the figures below. The new water lines are 4, 6, and 8 inches in diameter. The new system will meet fire flow requirements while not exceeding the City s maximum desired water flow velocity of 2.44 meters per second (8 feet per second). 568

13 Existing Water System New Water System METHODOLOGY Field investigations: The field investigations that were conducted as part of the preliminary engineering phase included: Topographic survey of the neighborhood which included all structure and out building lines, property lines, trees and shrubs, driveways and sidewalks, and site improvements. Information on trees included the diameter and type of tree. Some of the older trees had diameters of around 1.22 m (4 feet). Property owners were requested to mark the location of the sewer lateral at the back of their houses for planning the new lateral tie-in locations. Subsurface utility investigations included utility markings by the Virginia Miss Utilities organization. Existing utilities included water and sewer mains, storm drains, gas mains and communications cables. Utility test holes were dug in areas of potential utility conflicts with new sewer and water mains. Soil corrosivity evaluation consisted of taking soil samples along the proposed water main route and analyzing the soil corrosiveness in the laboratory. The soils were found to be corrosive, and polyethylene wrapping of the ductile iron water mains was recommended and included in the design. 569

14 Soil borings to assess new pipe and manhole bedding requirements. Soil borings to the along the proposed sewer main routes were made at about every m (500 linear feet). Project Constraints There were a number of project constraints that needed to be resolved in order to design the new water and sewer mains as follows: Tapping the City water main: The existing water mains tied into a City water main located in a major four lane divided roadway. In order to avoid traffic disruption, the City required the contractor to make the new water main taps at night when traffic volume was low. The contractor used a detailed traffic control plan that was approved by the City as part of the design package. Maintaining water and sewer service during construction: The new water mains were constructed on the opposite side of the street from the existing mains and water service was transferred to the new main as it was advanced up the streets. The plan for the suggested sequence of construction was to install the sewer and water lines on one street at a time to avoid traffic disruption. The contractor opted to install the water system first and make all new connections prior to installing the sewer. The sewer mains were installed in the street with laterals up to the property lines. Connections to the existing backyard sewers remained in order to maintain service while the new sewers were being constructed. When all of the new sewers were in place, the contractor began rerouting the service laterals to the new street sewers. Sewer Constructed After Water Line (White Oak Drive) 570

15 Water Main Removed to Install New Sewer (Englewood Drive) Small Backhoe Used for Lateral Installation Along several reaches of the new sewer, the existing sewer was located in the same area as the new sewer and had to be removed. A sewer bypassing plan was developed to allow removal of the existing sewer pipe and installation of the new pipe. The contractor had initiated bypassing, but determined that the day time, dry weather flows we so low that he could temporarily plug upstream existing sewers, let them surcharge and then remove sections of pipe to allow the new sewer to be installed in its place. The existing sewer was about the same elevation of the new sewer, so at the end of each day, the contractor made a temporary connection to maintain flow. 571

16 Bypassing for Sewer Removal / Replacement Existing Sewer Removed and Replaced in Same Trench (Ravenswood Drive) Traffic Control Plan: The City required that a detailed traffic control plan with detours and signage be part of the design project. This requirement added to the design cost. For the most part, the contractor was able to control traffic in the neighborhood without setting up detours. This deviation was approved by the City inspector. Not using the approved traffic control plan resulted in a cost savings for the contractor. New Sewer Lateral Routing: Since the sewer laterals along the backyard sewers were located in the back of the houses, the laterals needed to be routed either around the house to the street or the plumbing under the house needed to be rerouted to allow the lateral to exit from the front of the house. Locating the new laterals on each property required an extensive process that involved home owner participation as follows: 572

17 The first step was inspecting and photographing properties to document the existence of features that could impact lateral routing. Discussions were held with property owners during the field inspections to hear their concerns. Maps of the proposed lateral routing plans were sent to each property owner with a form requesting their acceptance of the proposed routing. They were requested to sketch-in any information on the location of abandoned septic tanks or underground fuel oil tanks on the map and return it to the designer. An example of the lateral routing maps is shown below. Lateral Routing Map A public meeting was conducted at a nearby elementary school to describe the project to the residents and to get feedback from property owners. Some property owners requested changes to the lateral routing to avoid hardscaped improvements. One property owner was particularly proud of his lawn which was an exotic type of Australian grass, Zoysia Grass. The design included the requirement that the contractor restore any of the grass that was disturbed in front of his house with the same type of grass. That made the home owner very receptive to the project. 573

18 Property with Zoysia Grass Subsequent follow up as the new sewers were constructed. At one house, it was determined that the lateral could not be routed around the house as shown in order to avoid damage to two large Oak trees. We met the home owner in the field and proposed an alternate routing on the other side of the house that he approved. Proposed Lateral Would Impact Big Trees In another case, a new home owner was concerned about the condition of the drain piping under their house (in the crawl space) and proposed that the pipes under the house be rerouted to have the lateral exit at the front of the house and connect to the street sewer. The bid form for the project included a line item for the contactor s plumber to turn around piping under houses. So, this change was easily accommodated prior to construction of the new sewer along the street where the new home owner was located. House lateral minimum slopes. Another consideration in design of the new house laterals was the minimum slope required by the local building code, 1%. This 574

19 could become an issue at the end of the main line sewer where it is shallower and long lateral runs may be necessary. The new mainline sewer has one tie-in to an existing manhole in the four lane street. This set the beginning invert elevation of the new sewer. Once the preliminary layout and grades of the new mainline sewers were determined, each proposed sewer lateral was checked to make sure that the lateral could be routed around the house and be at a depth of about 0.61 m (2 feet) where it would tie in to the existing house lateral. A spreadsheet was developed to make the calculations. It included the proposed invert of the mainline sewer connection at each house, the proposed lateral length, and the calculated depth of at the lateral tie-in while maintaining minimum slope. We were successful! The last house at the end of the line where the new sewer was shallowest had a lateral depth of slightly deeper than 0.61 m (2 feet). RESULTS As of the date of this conference, all of the new sewer and water lines had been constructed and all tie-ins to existing sewer laterals were well under way. The next step will be to CCTV the new sewers for acceptance by the City. The existing roads in the neighborhood will be milled and a new asphalt surface coat will be installed. The project was constructed with minimal disruption to existing landscaping, trees, shrubs, and other physical features. The photographs below show how impacts were minimized and mitigated. Lateral Installed Between Existing Features 575

20 Zoysia Grass Sodding After Water Main Constructed New Water Service Avoided Landscaping Conflicts with Post Design Additions Avoided 576

21 DISCUSSION As the construction project progressed, the contractor made changes to the sequence of construction which saved him time and money, and did not result in water and sewer service disruption or major traffic access issues. Changes included avoiding detours and signage and extensive bypass pumping. This demonstrates that even though certain aspects of a design are necessary to get approvals by the owner s agencies, the contractor can often figure out an alternative way to get the job done that works to his advantage. CONCLUSIONS Doing extensive preliminary field investigations and working closely with property owners both during design and construction are important to a successful backyard sewer replacement project. A backyard sewer replacement program can be successful if the following elements are part of the design and construction process: Gaining an understanding of the history of the existing utilities and how they came to be where they are. Conducting thorough subsurface utilities locating. Locating and naming all major topographic features during the topographic survey. Doing detailed field reconnaissance and making contact with property owners to assess lateral routing constraints. Working with homeowners to get project buy-in including consent letters and public information meetings. Being flexible during construction to address changing conditions and to address new concerns by property owners. This project was constructed with very minimal complaints by the area residences. The project will likely increase the value of their properties by having new, sustainable sewer and water systems. REFERENCES None. End of Manuscript. 577