DESIGN MEMORANDUM, 1430 S. DONOVAN STREET RESIDENTIAL YARDS AREA LDW Superfund Site Terminal 117 Early Action Area

February 6, 2013

Integral Consulting Inc. 411 1st Avenue S. Suite 550 Seattle, WA 98104 telephone: 206.230.9600 facsimile: 206.230.9601 www.integral-corp.com

MEMORANDUM

To: Piper Peterson

Cc: Mary Mitchener

From: Eric Pilcher, Linda Baker

Date: February 6, 2013

Subject: Final Design Memorandum for Removal Action at 1430 S. Donovan Street, Appendix H to T-117 Residential Yards Removal Action Design Report

Project: T-117 Residential Yards Cleanup

This removal action design memorandum presents design details for removal of soil from the front yard of 1430 S. Donovan Street in Seattle, Washington. This final memorandum responds to EPA comments to 1) clarify the excavation areas and 2) update the restoration plan based on feedback from the property owner.

The City of Seattle (City) was directed to perform this soil removal in a letter from the U. S. Environmental Protection Agency (EPA), dated September 5, 2012, as part of the Residential Yards cleanup within the Terminal 117 Early Action Area (T-117 EAA). The EPA directed the removal in this yard based on the presence of dioxin/furans at levels exceeding 50 nanograms per kilogram toxicity equivalency (ng/kg TEQ), which is EPA’s default value for federal action at the T-117 EAA.

In a conditional approval letter dated November 20, 2012, EPA required revisions be made to the removal action design report (RADR). One of the required revisions was the preparation of this design memorandum to more thoroughly detail the removal action at 1430 S. Donovan Street. This design memorandum is Appendix H to the RADR. The remaining EPA required revisions were addressed separately and revised documents were submitted to EPA on November 30, 2012. EPA provided approval of these documents and authorization to proceed with the removals at all properties except for 1430 S. Donovan Street in an email dated December 4, 2012.

This design memorandum supplements the RADR, providing details specific to the additional removal action at 1430 S. Donovan Street. Unless stated otherwise, the design

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basis and construction requirements described within the RADR and appendices are applicable to 1430 S. Donovan Street. The following portions of the RADR are hereby amended to include the additional information presented herein.

Section 1.3 Removal Action Objectives

The removal action objectives are hereby amended to state that, based on EPA direction, the City will remove soil from the front yard of 1430 S. Donovan Street (decision unit 23 [DU 23]) with dioxin/furan concentrations greater than 50 ng/kg TEQ. As indicated below, previous sampling in DU 23 identified soil from 0 to 0.2 ft below ground surface (bgs) with a dioxin/furan concentration greater than 50 ng/kg TEQ. The dioxin/furan concentrations in deeper soil from 0.2 to 0.5 ft bgs were below 50 ng/kg TEQ.

Section 2.2 Nature and Extent of Contamination

Section 2.2 of the RADR is amended to provide information on the nature and extent of dioxins/furans contamination at 1430 S. Donovan Street. Existing sampling results for dioxins/furans at 1430 S. Donovan Street were summarized in a letter to EPA from the City dated October 5, 2012.

Previous sampling reported dioxin/furan concentrations in soil from 0 to 0.2 ft bgs in the front yard of 1430 S. Donovan Street at 80.3, 83.4, and 83.7 ng/kg TEQ, exceeding the 50 ng/kg TEQ default value for federal action. Dioxins/furan concentrations from 0.2 to 0.5 ft bgs measured 29.7 ng/kg TEQ, less than the default value. The removal has been designed for constructability to extend to a minimum depth of 0.5 ft.

Section 3.5 Soil Excavation and Material Handling

Section 3.5 of the RADR is amended to include design details for 1430 S. Donovan Street. Detailed construction drawings added to Appendix A of the RADR are included in Attachment 1. Table 3-1 of the RADR which provides a summary of excavation design details including area, depth, estimated volume, and removal elevations is revised to include 1430 S. Donovan Street. The revised Table 3-1 is included in this Design Memorandum as Attachment 2.

Section 4.5 Cost Estimate

Section 4.5 of the RADR is amended to include the cost for the addition of 1430 S. Donovan Street to the Residential Yards Cleanup. This increases the Engineer’s construction cost estimate by $50,000 to a total of $1,050,000.

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APPENDIX A1: CONSTRUCTION DRAWINGS

Appendix A1 of the RADR is amended to include construction drawings for 1430 S. Donovan Street. These additional construction drawings are in Attachment 1 to this Design Memorandum and include site plan, excavation plan, hardscape plan, existing landscape conditions, landscape restoration plan, and details. EPA and property owner approval of these plans are required prior to implementing the cleanup at 1430 S. Donovan Street yard.

APPENDIX A2: TECHNICAL SPECIFICATIONS

Section 01 71 23 Field Engineering

Part 3.04, paragraph C.2 is amended to include Existing Conditions Documentation at 1430 S. Donovan Street.

APPENDIX D: COMMUNITY HEALTH AND SAFETY PLAN

The Community Health and Safety Plan (HASP) text was previously amended to include 1430 S. Donovan Street. However, key figures require revision. Figures 1-1 and 2-1 are amended to include 1430 S. Donovan St.

Enclosures Attachment 1. Drawing Sheets 29 through 31 of 31 Attachment 2. RADR Table 3-1 Attachment 3. Community HASP Figures 1-1 and 2-1

ATTACHMENT 1 DRAWING SHEETS 29 THROUGH 31 OF 31

 

ATTACHMENT 2 RADR TABLE 3-1

 

T-117 Residential YardsRemoval Action Design Report January 8, 2013

Integral Consulting Inc. Page 1 of 1

Table 3-1. Excavation Depths, Elevations, and Quantities

Affected Property, Ownership, and Decision Unit

Minimum Removal Depth

(ft bgs)a

Lowest DU Elevation

(ft NAVD88)

Target Removal Elevation

(ft NAVD88)Removal Area

(sf)

Removal Volume

(cy)b

8523 Dallas Avenue S. (Security National Mortgage)DU01 1.0 17.9 16.9 1,878 121.4

1410 S. Cloverdale Street (McKnight)DU03 2.0 18.7 16.7 2,829 261.3

1421 S Cloverdale Street (Hill)DU36a 1.5 20.1 18.6 233 17.6 DU36b No Removal - - - -

1425 S. Cloverdale Street (Collins/Johnson)DU35 2.0 19.9 17.9 1,747 132.9 DU35a 2.5 19.9 17.4 770 73.7

1440 S. Cloverdale Street (Collins/Malagon)DU14 1.0 19.5 variesd 3,198 154.0

1445 S. Cloverdale Street (Barnett)DU32a 0.5c 20.4 19.9 749 23.1 DU33a 1.0 20.6 19.6 546 25.4 DU33b No Removal - - - -

1418 S. Donovan Street (Carroll)DU25 2.0 19.6 17.6 864 93.2 DU25a No Removal - - - - DU25b No Removal - - - -

1430 S. Donovan Street (Colson)DU 23 0.5c 23.2 variese 715 30.6

Yard Subtotal 13,529 933.3

S. Cloverdale Street Planting Strip, North (Seattle DOT)PS North A 1.0 19.1 18.1 947 48.5 PS North B 2.0 19.8 17.8 359 35.5 PS North C 1.0 20.2 19.2 260 15.2

S. Cloverdale Street Planting Strip, South (Seattle DOT)PS South A 2.0f 19.2 17.2 305 29.7 PS South B 2.0f 19.5 17.5 348 34.0 PS South C 2.0f 19.9 17.9 642 63.1

Planting Strip Subtotal 2,861 226.0

Southern Alleyway (Seattle DOT)14a, 14b, 14c 2.0 21.2 19.2 1,086 91.0 15a, 15b, 15c 2.0 20.5 18.5 1,531 153.8 16a, 16b, 16c 1.0 20.1 19.1 733 42.9 17a, 17b 1.0 19.7 18.7 1,419 80.2 21a, 21b 3.5, 3.0 21.1, 20.5 17.5 839 112.1

Northern Alleyway (Seattle DOT)18b No Removal - - - - 19b No Removal - - - - 20b No Removal - - - -

Alleyway Subtotal 5,608 480.0

Project Total 21,998 1,639.3 Notes:

a Minimum removal depth defined by pre-design confirmational sampling concentrations below the removal action level of 1.0 mg/kg. Refer to the pre-excavation confimation sampling results for the Residential Yards study area (Appendix G of the removal action design report; Integral 2012).b Based on level excavation at the target elevation across the entire decision unit.

f Removal depth was not pre-confirmed due to presence of shallow utility line. Additional excavation may be necessary based on post-excavation confirmation sampling results.

c 0.5 ft held as minimum excavation depth. Pre-design confirmation sampling indicated non-exceedence below 0.2 ft.

e Target elevation varies from 22.7 to 24.5 ft NAVD 88 based on discrete areas within the yard.

d Target elevation varies from 18.5 to 19.5 ft NAVD 88 based on discrete areas within the yard.

ATTACHMENT 3 COMMUNITY HASP FIGURES 1-1 AND 2-1

 

Figure 1-1.T-117 Early Action Cleanup Site Overview

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Figure 2Soil Excavation Boundaries for Residential YardsLower Duwamish Superfund Site - Terminal 117 Early Action Area