Combined Sewer Overflow Reduction Program Briefing

Transcription

1 F e b r u a r y 8, 2 0 Combined Sewer Overflow Reduction Program Briefing S e a t t l e C i t y C o u n c i l S e a t t l e P u b l i c U t i l i t i e s & N e i g h b o r h o o d s C o m m i t t e e

2 Commitments for Next 5 Years Comply with current NPDES Permit, Administrative order and Consent Decree negotiations: Improving existing system through retrofits Constructing CSO projects Windermere, Genesee, and Henderson basins Implementing green infrastructure projects in Ballard Completing Long-term Control Plan

3 Genesee CSO Reduction Project Top Priority Basin 700 Acres Construction Reduces CSOs from 0 times to time per year Storage Volumes: Basins 40/4: 430,000 gal Basin 43: ~250,000 gal

4 Basin 40/4: Storage Sites Considered A: Pipeline storage along Lake Washington Blvd and new pump station at Genesee Park B: Triangle Parking Lot (recommended) C: Private Property Acquisition (would require acquisition of 3-5 properties around Lake Washington Blvd and 49 th Ave S.)

5 Basin 43: Storage Sites Considered Alternative D Alternative B Alternative A A: 54 th Ave S. B: Open Space at 54 th Ave S and S. Alaska St. C: Private property acquisition (would require acquisition of up to 5 properties around S. Alaska St & 54 th Ave S.) D: 53rd Ave S. & Lake Washington Blvd Parking Lot (recommended)

6 Genesee Project: Community Feedback & Report Out Pipeline storage on 54 th Ave S has significant construction impacts on private property owners. Underground storage in open space at S. Alaska St and 54 th Ave S is less impacting, but green space and trees should be protected as much as possible. Consider parking lot at 53 rd Ave S and Lake Washington Blvd as alternate site. Consider private property along S. Alaska Street. Consider constructing along S. Alaska Street instead of 54 th Ave S. If a Parks site is selected, constructing the tank underneath an existing impervious surface (e.g., parking lot) is least impacting.

7 Henderson CSO Basins Top-Priority for CSO reduction,800 Acres North Henderson South Henderson Seven basins CSOs discharge approximately 7 times per year Storage Volumes: Basins 44: 2,000,000 gal Basin 45: 200,000 gal Construction must begin in 205

8 North Henderson Workshops November 8, 200 Presented CSO reduction options (storage, transfer, separation, treatment) Obtained feedback to consider separation, inflow/infiltration reduction, and more innovative technologies to reduce CSOs. Obtained input on community values and concerns December 4, 200 Present site-specific CSO reduction alternatives Obtain feedback on alternatives Confirm evaluation criteria (i.e., community values and concerns) Weight relative importance of evaluation criteria January 9, 20 Present results of alternatives evaluation Obtain feedback on results Narrow down site-specific alternatives

9 Summary of Alternatives Distributed Storage Basin 44 (Storage under private property, Seward Park parking lot, or Lake Washington Blvd) Basin 45 (Storage under private property, Martha Wahsington Park open space, or 57 th Ave S.) Tunnel Storage Conveyance and Storage Complete Sewer Separation (includes Inflow & Infiltration Reduction)

10 North Henderson Project: Community Feedback & Report Out Private property acquisition is significantly opposed. General public support for the Distributed Storage alternative. Strong interest in preserving the character and use of Seward Park and Martha Washington Park. General opposition to the Tunnel alternative. Some public support for the Complete Sewer Separation alternative.

11 Ballard Area Combined Sewer Overflows (CSOs) Two overflow points (NPDES 50/5, 52) Approximately overflows per year Approximately million gallons of overflow per year In December 200: 23 million gals CSO 0 CSO events

12 Ballard Area CSO Reduction Solutions Retrofits Make small modifications to existing infrastructure to maximize existing system capacity. Green Allows stormwater to slowly filter into ground, keeping it out of sewer system; applicable to public and private property Storage Increase capacity of underground pipes and tanks. B a l l a r d o ff e r s a u n i q u e o p p o r t u n i t y f o r g r e e n s o l u t i o n s

13 Ballard Roadside Raingardens Pilot project was designed and constructed in 200 Installed 0 blocks of roadside raingardens; total of 93 raingarden cells Additional plants will be planted in the Spring 20. Pilot Project

14 Performance 66 E2 B 66 E2 A Monitoring W3 66 W2 D 66 W2 C 66 W2 B 66 W2 A 66 W C 66 W B 66 W A 66 E B 66 E A Performing at design standards Not performing at design standards but expected to meet them by fall 20 Not performing at design standards NW 66 th St 65 W4 65 W3 B 65 W3A 65 W2 B 65 W2 A Not raingarden 65 W 65 E2 65 E B 65 E A S o m e o f t h e r a i n g a r d e n s have n o t p e r f o r m e d a c c o r d i n g t o t h e d e s i g n c r i t e r i a. Raingardens not exactly to scale.

15 Performance Monitoring Summary Raingardens that are draining within 72 hours Raingardens not meeting performance standard; but are expected to meet performance standard after plant establishment Raingardens that are not draining within 72 hours 9

16 Ballard Roadside Raingardens Pilot Project: Community Feedback & Report Out Raingardens are not draining within 72 hours; standing water is unacceptable because of health and safety. There are too many signs, they are unnecessary, and they do not fit in this residential neighborhood. The raingardens are ugly, and my property value has gone down. The raingardens are too deep and the slopes are not safe.

17 What has SPU learned from this pilot project so far, and what are we doing about it? We need to slow down and take more time as we roll these out to other neighborhoods. We need to improve our neighborhood communications throughout the development and construction process. We need to review our performance standards for these facilities to better address citizen concerns. We need to institute a modification process during construction to accommodate changing site conditions.

18 Past Project Example: Broadview Greengrid Just planted +4 years - winter

19 Contact Information