Regional Connector Transit Project

Transcription

1 Regional Connector Transit Project Public Hearing June 30 and July 7, 2015 Project Update

2 Public Hearing Agenda 1. Open House 2. Presentation on SEIS Purpose and Tunneling Method Alternatives 3. Public Comments 2

3 Regional Connector Transit Project Based on two decades of planning and environmental review Final EIS was prepared for the Locally Preferred Alternative (LPA) approved by the Metro Board of Directors on April 26, 2012 Federal Transit Administration (FTA) issued a Record of Decision (ROD) on June 29,

4 Purpose of the SEIS Per Order of the U.S. District Court issued May 28, 2014 Draft Supplemental Environmental Impact Statement (DSEIS) prepared to provide additional detail on tunneling methods not selected for construction along Flower Street between 4 th Street and the 7 th Street/ Metro Center Station, specifically: - Open-Face Shield - Sequential Excavation Method (SEM) 4

5 Flower Street Segment Challenges Flower Street has major underground constraints that impact tunneling Mesh of building foundation tie-backs and many utilities Unstable soils and challenging mixed-face geologic conditions Perched groundwater and hazardous gases 5

6 Locally Preferred Alternative (LPA) 6

7 LPA Construction Elements LPA designed to address Flower Street segment challenges EPBM tunneling north from 4 th Street is most viable tunneling method given underground conditions of Flower Street segment Cut and cover construction - Allows for safe removal of tie-backs - Minimizes risk of ground loss and settlement due to unstable soils and geologic conditions - Vents hazardous gases - Minimizes risk of encountering utilities during construction 7

8 SEIS Project Alternatives Two tunneling method alternatives were identified to evaluate the use of other tunneling techniques on Flower Street: Alternative A a combination of Earth Pressure Balance Tunnel Boring Machine (EPBM), Open-Face Shield, and Sequential Excavation Method (SEM) construction methods Alternative B a combination of EPBM and SEM construction methods 8

9 Ground Stabilization Ground stabilization required for Open- Face Shield and SEM tunnel methods Jet grouting recommended given soil conditions on Flower Street Mix of cement grout and soil is injected to form a grid of 6-foot diameter columns extending 40-feet below grade - Alternative A requires 1,900 jet holes - Alternative B requires 1,000 jet holes Even with grouting, total ground stability is not assured given Flower Street underground conditions 9

10 Tunneling Method Alternative A 10

11 Tunneling Method Alternative B

12 Construction Schedule Impacts Comparison of Construction Schedule Impacts Construction Duration Change in Construction Duration (Over Project) Required Preconstruction Activities Total Project Delivery Duration Revenue Service Date Total Project Delivery Delay (Over Project) Alternative Months Months Months Months Date Months Years The Project Mid Alternative A Early Alternative B Mid

13 Excavation Material Handling Excavation Activity on Flower Street and in Little Tokyo Hauling of Excavated Materials from Flower Street On Flower Street Percentage of total Flower Street materials Duration of hauling activities In Little Tokyo Percentage of total excavation activities Duration of hauling activities Excavation/Construction Trucks Per Day Impact The Project Alternative A Alternative B 81% 9 Months 19% 2.5 Months 25% 1 Month 75% 19 Months 20% 1 Month 80% 17 Months On Flower Street In Little Tokyo Duration of Truck Impacts (for hauling excavated materials) 9 Months 19 Months 10 Months longer 17 Months 8 Months Longer 13

14 Public Comments Public comment period through 5pm on July 27, 2015 Complete comment form - At a Public Hearing June 30 at Central Library July 7 at JANM - By Mail: Dolores Roybal Saltarelli, Project Manager One Gateway Plaza, MS Los Angeles, CA Via web: regionalconnector@metro.net 14