May 9, 2014 Dear Resident: On Thursday, April 24, 2014, at the monthly First Street Tunnel Forum Meeting, DC Water discussed the removal of planter boxes (tree boxes) at the intersection of First and V Streets NW and north and south along First Street near V Street. Removal of the planter boxes is necessary to safely accommodate traffic lanes during construction of the First Street Diversion Chamber. Following the discussion at the Tunnel Forum Meeting, members of the community expressed concern regarding the safety of pedestrians in the area. The purpose of this letter is to describe in more detail the work involved and the additional measures which will be taken to ensure the safety of area pedestrians. Throughout the design phase of the First Street Tunnel Project, DC Water developed mitigation requirements to minimize construction impacts based on input from project stakeholders including, but not limited to,

• DC Fire and Emergency Medical Services (DC FEMS), • Metropolitan Police Department (MPD), • District Department of Transportation (DDOT), • MedStar Washington Hospital Center, • Children’s National Hospital, MedStar National Rehabilitation Hospital, • Veterans Affairs Medical Center, and • the Bloomingdale community.

Major areas of concern that were common among project stakeholders during these coordination efforts were parking and traffic impacts. Based on feedback received from the stakeholders, DC Water developed a Maintenance of Traffic Plan that maintained two-way traffic along First Street NW at all times during construction, except for an eight-month period when the First Street Diversion Chamber will be under construction. During this eight-month period, First Street NW will be limited to one lane northbound only. The following narrative describes the technical basis for temporarily eliminating parking and removing the existing curb and planter boxes along First Street NW, in the vicinity of the V Street Construction Staging Area.

May 9, 2014 Maintenance of Traffic Page 2 of 8 As illustrated in Figure 1, the existing First Street Trunk Sewer is located along the center of First Street NW. The sewer terminates at V Street NW. Overflow at this termination point is a primary contributor to flooding in the neighborhood. In order to divert flow from this sewer, a diversion chamber (First Street Diversion Chamber) must be constructed at the end of the pipe to send flow (that typically would flood the area) to the new First Street Tunnel, which will be located approximately 80 feet below the existing sewer. The diversion chamber is required to be approximately 45 feet deep to capture flows from the sewer and deliver them to the tunnel. (See Figure 3 for more specifics on the First Street Diversion Chamber.)

Figure 1. Intersection of First and V Streets NW showing the Existing First Street Trunk Sewer

May 9, 2014 Maintenance of Traffic Page 3 of 8

Because the excavation required to construct the First Street Diversion Chamber is very deep, Skanska will need to support the ground around the perimeter of the proposed structure using concrete cylinders called “secant piles.” The secant piles will support the ground and prevent ground movements around the excavation, minimizing impacts to adjacent structures. Figure 2 illustrates a typical secant pile wall, which was described to the community during the January 2014 outreach meetings.

What is a Secant Pile? 9" for guide wall

Guide wall

8" to site perimeter fence

6"–8" concrete cover at secant pile

3'-8" – 4'-4" distance from edge of permanent structure to site perimeter fence

Very common type of support used for

vertical excavation in areas with high water table

• Vertical steel soldier piles used to support the earth load

• Excellent for water cutoff

• Rigid walls good for protecting adjacent structures

Secant pile construction steps (top diagram): • Step 1 – Install guide walls

• Step 2 – Install secondary wall piles (green) – act as lagging

• Step 3 – Install primary wall piles with soldier pile (blue) – take the load

• Excavate and install struts (cross-supports, shown in photo at right)

3" construction tolerance

TOP PLAN VIEW Edge of permanent structure

Steel section: 18"– 24"

Figure 2. Images of Typical Secant Pile Wall

May 9, 2014 Maintenance of Traffic Page 4 of 8

Figure 3 illustrates the eastern secant pile wall and construction staging area necessary to construct the First Street Diversion Chamber. As illustrated, most of the travel area along First Street NW will be used, leaving only 5 feet between the construction staging area fence line and existing curb. This distance is not enough to maintain the minimum travel lane requirement of 10 feet. Therefore, the curb and planter boxes need to be removed to accommodate traffic. A temporary 4-foot-wide sidewalk will be installed for use while the First Street Diversion Chamber is being constructed.

Figure 3. Site Plan of V Street Construction Staging Area and Existing Curb Conditions

May 9, 2014 Maintenance of Traffic Page 5 of 8 Figure 4 illustrates the plan and general cross-section of the proposed northbound travel lane along First Street NW with the modified curb line. The purpose of the reinforced concrete barrier shown in the cross-section is to safely separate vehicular traffic from pedestrians using the sidewalk. The 10-ft wide lane for vehicular travel plus the thickness of the proposed reinforced concrete barrier and buffer distance from the construction staging area fence totals approximately 12 feet. Therefore, the existing curb, planter boxes, and portions of the sidewalk will temporarily be removed to support traffic operations in the areas shown on Figure 5. Parking will also be restricted in this area to accommodate the lane shift and travel lane northbound.

Figure 4. Site Plan and Cross-section of V Street Construction Staging Area and Modified Curb Line

May 9, 2014 Maintenance of Traffic Page 6 of 8

Figure 5. Addresses Surrounding the Construction Staging Area. For addresses shown in green, please remove any personal items from the planter boxes that you wish to save (bushes, shrubs, ornamental grasses, border stones, or other materials) by May 30, 2014.

May 9, 2014 Maintenance of Traffic Page 7 of 8

After the eastern portion of the First Street Diversion Chamber is completed, two-way travel will resume through this intersection. At that time, Skanska will complete construction on the other portions of the diversion chamber as shown in Figure 6.

Figure 6. Two-way Maintenance of Traffic Plan at First and V Streets NW

May 9, 2014 Maintenance of Traffic Page 8 of 8

The proposed Maintenance of Traffic Plan to accommodate First Street NW travel was developed in accordance with the DDOT-approved traffic study and meets District standards (including Americans with Disabilities Act guidelines), as well as the requirements of the project stakeholders. Upon completion of the work at the intersection, structures will be restored to equal or better conditions. In conjunction with Skanska, DC Water will continuously monitor this area to ensure safe travel is maintained for both pedestrians and vehicular traffic. If issues should arise with the proposed plan, DC Water will revisit and revise the traffic measures with the appropriate level of stakeholder input. Mitigating construction impacts to the project stakeholders is of the utmost importance to DC Water and Skanska. We understand that certain services (e.g., trash and recycling pickup) may be impacted as part of the implementation of this project. We will work directly with residents to ensure their needs are met. Please note that while DDOT has approved the overall plan of maintaining travel lanes along First Street NW during construction of the V Street Facilities, they have not yet approved the details associated with the concrete barrier and sidewalk (e.g., materials, heights, widths). DC Water and Skanska are currently pursuing the required permits to complete the work at the V Street Construction Staging Area through District agencies, including DDOT. Therefore, some of the temporary details associated with the maintenance of traffic plan may change prior to construction. We will continue discussions on this project with you at the next Tunnel Forum Meeting on Thursday, May 29, 2014. We want to stress that this plan was developed with your safety in mind. We look forward to working with you and toward our shared goals of mitigating flooding and restoring your neighborhood to as beautiful as it was before construction, and better.

If you have any questions, please feel free to call the hotline at 844-FST-INFO (844-378-4636) and we look forward to seeing you on May 29th.

Sincerely,

Tom Lindberg DC Clean Rivers Project / First Street Tunnel Public Outreach Lead

c: Councilmember Kenyan R. McDuffie, Ward 5

James M. Cheeks, Jr., Manager, Transportation Operations Administration, DDOT Dierdre N. Porter, Fifth District Commander, MPD