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in association with

WSSC Bi-County Water Tunnel Rock Creek Hills Community Meeting October 8, 2009. in association with. PEER Consultants Haley & Aldrich McKissack & McKissack T. L. Brown A. Morton Thomas Dacco Sci. Closing the Gap in the Water System Backbone. Potomac

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  1. WSSC Bi-County Water Tunnel Rock Creek Hills Community Meeting October 8, 2009 in association with PEER Consultants Haley & Aldrich McKissack & McKissack T. L. Brown A. Morton Thomas Dacco Sci

  2. Closing the Gap in the Water System Backbone Potomac Water Filtration Plant Montgomery County Bi-County Water Tunnel Prince George’s County

  3. Overall Alignment

  4. Why Is It Needed? • Enhance reliable water supply to eastern region of the system • Maintain adequate water pressures in the Silver Spring/Wheaton area • Implement concurrent with projected low water pressures

  5. Basic Project Timing

  6. Tunnel Shaft Construction

  7. Tunnel Cross-Section

  8. Connecticut Avenue Shaft (S3)Working Shaft (Looking North) • Primary shaft/work site • Install TBM • Spoils/Muck Removal • Material delivery • Liner Installation • Grouting • Construction Field Offices Connecticut Ave. Ramp

  9. Connecticut Avenue Working Shaft • Tunneling goes both directions: Toward Stoneybrook Shaft & Tuckerman Shaft • Rock and water from Tunnel removed through this shaft • Primary location for installing pipe & appurtenances

  10. Truck Access from Conn. Ave Ramp to S3

  11. Truck Routes (Shaft S-3) Truck Entrance Truck Exit

  12. Stoneybrook Shaft (S4)Beach Dr & Stoneybrook Pkwy (Looking NE) • Connection to existing 96” pipeline • Some pipe & grouting • Access from Stoneybrook • Restoration with grass & trees Existing Shaft Stoneybrook Pkwy Stoneybrook Pkwy Beach Drive Beach Drive I-495 I-495

  13. Stoneybrook Shaft Access

  14. Major Construction Traffic Est.All Shaft Locations

  15. Montgomery County Noise Ordinance (MC Code 31B) • Construction regulations 7a.m. – 5 p.m. weekdays • 85 dBA (with approved plan) • At 50’ from source at property line-where noise is greatest • Points of reference1: • 50 - 75 air conditioner • 50 - 80 electric shaver • 75 - 85 flush toilet • 70 freeway traffic • 85 heavy traffic, noisy restaurant • Other times, 65 dBA daylight and 55 dBA nighttime • Waivers for specific activities possible • 65 - 95 lawn mower • 105 snow blower • 110 power saw • 110 leaf blower • 125 chain saw • 130 jack hammer 1 References from the League for the Hard of Hearing www.lhh.org

  16. Stoneybrook Shaft (S-4)1000’ from Blast Controlled Blasting Notifications 1,000 ft Radius

  17. What Precautions are takenin Controlled Blasting? • Work is being performed by experienced contractor under the supervision of a blasting consultant • Vibration limits are set to ensure no damage to property • Vibration will be vigorously monitored using seismographs • The Contractor must comply with all federal, state, and local ordinances

  18. What Precautions are takenin Controlled Blasting? • Residents within 1000’ of the blast will have opportunity to participate in a pre-blast survey of their home • Residents within 1000’ of the blast will receive door hanger notification at the start of blasting • Air horns will “announce” each blast • A Cover will be used to contain blast material and muffle sound

  19. Connecticut Ave. Shaft (S-3)PPV = 0.2 in./sec (Noticeable)would be between 400 and 800 ft. from blast 800 ft 400 ft 800 ft 1,000 ft 400 ft

  20. Stoneybrook Shaft (S-4)PPV of 0.2 in/sec (Noticeable) would be between 400 and 800 ft. from blast 1,000 ft 800 ft 3,000 ft 400 ft 1,500 ft

  21. General Guideline Limits of Vibration For Illustrative Purposes Only 1. Noise may make perception of vibration seem worse than actual.

  22. Blasting Sound Levels Nearest Residents: Noise in this range: less than 1 second of sound below that of a garbage disposal or lawn mower

  23. Current Status • Construction Started August 3, 2009 • Work proceeding at the Connecticut Avenue Shaft • Controlled Blasting to Start in Late October • Controlled Blasting Complete – around Christmas • Stoneybrook Shaft • Site Work to start in November • Blasting notification, public meeting and photo surveys for residents within 1000’ (Nov. 2009 –Jan 2010) • Begin Shaft Construction (Jan. 2010)

  24. Questions and Answers

  25. Back Pocket Slides

  26. Water Storage Facility North Woodside Standpipe Tank Level Tank Full – Elev. 495 (45 psi) With Bi-County Water Supply Main - Elev. 478 (37 psi) Without Bi-County Water Supply Main - Elev. 462 (30 psi)

  27. Tuckerman Shaft (S1)I-270 and Tuckerman Lane (Looking West) • Connect to existing 96” pipe • Removal of TBM • Pipe installation • Grout installation • Truck Access-Tuckerman • Other Access-Old Club Ct. • Restoration: reforestation & stream bank improvements I-270 Tuckerman Lane Daybreak Ct. Old Club Ct.

  28. Typical Controlled Blasting Sequence • Drill holes • Load charges • Blast • Muck out debris (½ day) • Support walls (½ day) • Repeat sequence

  29. Requirements for Controlled Blasting • Blasting required for shafts, tail tunnel, starter tunnel • Contractor must comply with all Federal, State and County Codes • Contractor must use experienced, independent, licensed Blasting Consultant • Blasting Plan must be submitted for approval prior to blasting • Peak Particle Velocity limited to < 1 inch/sec at nearest structure or utility • Reports on vibration monitoring data required after the blasting • Blasting limited to daylight hours.

  30. Hypothetical Blasting Operation • Assume maximum charge density per delay of 65 lbs (25-ft. column at 2.5 lb./ft.) • Then, may expect: • PPV of 0.2 in/sec (distinctly perceptible) would be between 400 and 800 ft. from blast • PPV of 0.02 in/sec (barely perceptible) would be between 1,500 and 2,000 ft. from blast (Note: actual blasting charge density will be determined by permit and contractor’s blasting methods.)

  31. Vibration Monitoring Source: US Dept. of Transportation For Illustrative Purposes Only 1. Noise may make perception of vibration seem worse than actual.

  32. Blasting Sound Levels A steel blasting cover and baffles will be used to muffle the sound generated by each blast. In addition, noise levels will be monitored during each blast. The table below present noise levels in decibels (dBl) for blasting without the use of a cover with respect to distance from the blast source.

  33. Vibration Monitoring Cell Tower Potential Monitoring Point Tunnel Shaft 170’R 560’R

  34. Blasting required for shaft and tunnel construction. Contractor must comply with all Federal, State and County Codes. Contractor has employed an experienced, independent Blasting Consultant, McKown Associates, LLC. Blasting Plan has been submitted for approval. Controlled blasting program has been designed to limit Peak Particle Velocity to < 1 in/sec at nearest structure. Reports on vibration monitoring data prepared after each blast. Blasting allowed between 7:00 a.m. and 7:00 p.m. or as otherwise allowed by the Montgomery County Fire Marshall. Controlled Blasting

  35. Frequently Asked Questions Will the nearby blasting cause my house to shift or create structural damage? No, the controlled-blasting program has been designed to maintain vibration levels below levels where residential structures have been documented to have been damaged by blasting-induced vibration levels. Controlled blasting can be performed within inches of structure without causing structural damage to it. Will blasting cause cracking in my driveway, sidewalks, or on my property? No, the blasting program has been designed to be a controlled-blast. The energy created by the blast decreases with distance from the source as the travel through rock and soil. The controlled blasting program for this project has been design such that vibration levels remain below Maryland regulatory standards and other project requirements for adjacent structures.

  36. Frequently Asked Questions If I believe blasting has caused damage to my house, what do I do? Notify the WSSC communications Manager, Mike McGill at 301-206- or by e-mail mmcgill@wsscwater.com. WSSC will notify the tunneling contractor who will schedule an appointment with you to review the damage. For those who had a pre-blast survey, we will compare photos with the area in question and will be able to resolve the matter quickly. If no pre-blast survey was conducted, additional coordination will be necessary to determine whether or not the blasting was the cause of the damage. If at any time you are not satisfied with the responsiveness, you may formally file a claim directly with WSSC. What if I am not satisfied with the contractors handling of a claim for damage? Notify WSSC of your concerns and we will work to address those issues. If you are still unsatisfied, WSSC has a claims office and you may file a formal claim through that office.

  37. Frequently Asked Questions Do the fumes released in the air by the explosion pose any health risk? While there is always a release of gases from the explosives which have the potential to be harmful, the amount and concentration of the gases are very low and will not pose any health risk to the surrounding environment. Will the construction around my home make it difficult to get in/out of my home? No, the construction will be taking place on site locations with private access roads. Traffic delays are not expected as a result of construction activity. How will I know when the blasting begins and when it is complete? Door hangers will be distributed 48 hours in advance. Go to WSSCwater.com for updates.

  38. Controlled Blasting Legwire for Blasting Cap Crushed Stone Stemming 4 Sticks 1-1/2”x16” Extra Gelatin (4x1.4 +/- lbs. Each) ------ 5.6 lbs. 1 Stick 2”x16” Extra Gelatin (2.5 lbs) Electric or Non-Electric Blasting Cap

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