1212 FOURTH ST., SUITE Z SANTA ROSA, CA 95404 PHONE: 707.526.0992 FAX: 707.526.0217

100 BUSH ST., SUITE 1850 SAN FRANCISCO, CA 94104 PHONE: 415.243.4091

2277 FAIR OAKS BLVD., SUITE 320 SACRAMENTO, CA 95825 PHONE: 916.924.7024 FAX: 916.924.7034

August 29, 2011

Maritza Delgadillo, Principal Architect

Asian Neighborhood Development 1245 Howard Street San Francisco, CA 94103 RE: Altamont Residential Hotel, Mission District, 3048 16th St, San Francisco Structural Assessment of the Surrounding Sidewalk Maritza: We provide herein our assessment and recommendations for the subject: sidewalk which forms the roof over the basement on three sides of the building. On-going maintenance and water ingress is the catalyst for the assessment and, as shown herein, is timely before the associated structural steel dilapidation results in an imminent hazard to the public. We include in our assessment two approaches to mitigation, a replacement and an augmentation of the existing, and a recommendation that the latter be selected based on our judgment of the effectiveness and qualitative assessment of costs of each solution. Orientation The main residence entrance in the south elevation is located on 16th Street; and the east and west elevations are located on Wiese St and Julian Ave, respectively. As shown in Figure 1 below, there are numerous ancillary components atop the sidewalk, such as light poles, mail boxes, parking meters, etc.

Figure 1.

Site Perspective

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Figure 2.

West Side, Julian Ave

Figure 3.

South Side, 16th Street

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Figure 4.

East Side, Wiese Street Sidewalk Structural Configuration Along the west and south sides the sidewalk extends approximately 10 feet out from the building and 2.5 feet on the east side. The sidewalk on the west and south sides is formed from cast-in-place concrete that arches off the bottom flanges of beams supported on the building frames and the perimeter unreinforced masonry walls located beneath the curb. Please see Figure 5 below for detail and Figure 6 for photo.

Figure 5.

Typical South (West Similar) Sidewalk Section

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Figure 6.

Concrete Barrel Arch Springing from Bottom Flange Note: Delamination of bearing plate atop of URM and bearing function is maintained

The west side is of slightly different configuration and consists of probably flat slab for the few feet of sidewalk. At the entryways, the slab has cracked and sunk downward, please see photos 29 through 32. Observations and Findings There is a systemic issue with water ingress through slab penetrations and cracks, along the curb line and, feasibly, down the face of the exterior wall and through the slab via a control joint. The water tracks along the underside of the slab, particularly along the top flange of beams. The resulting dilapidation is structurally significant and is more prevalent along the west side. The condition if left “as-is” will pose a Life Safety hazard. Please see figures below showing typical cause, and damage patterns and degree.

Figure 7.

Typical air vent to street above Note: Provides path for water to and along underside of slab

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Figure 8.

Boiler Room, South Side

Figure 9.

Boiler Room, South Side Note: Top flange corroded segment protruding and being pulled from original position

Figure 10.

Boiler Room, South Side Note: Main sidewalk beam web corroded through, typical at connection

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Figure 11.

Boiler Room, South Side Note: Manhole and access ladder

Note: Water ingress and spalled concrete

Figure 12.

Mechanical Room, South Side

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Figure 13.

Mechanical Room, South Side Note: Spalled concrete

Figure 14.

Mechanical Room, South Side Note: Most ducts and pipes are supported overhead by sidewalk slab

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Figure 15.

Fire Life-safety component wrapped and taped, and paint container used to deflect water

Figure 16.

South Side, Storage Room

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Figure 17.

Parking Meter Anchor

Figure 18.

South Side, Storage Room Note: Assumed metal deck with concrete fill localized repair

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Figure 19.

West Side, Storage Room (just south of CMU) Note: Street light pole anchorage and spalled concrete

Figure 20.

South Side, Storage Room – Perimeter URM Retaining Wall Note: Plaster removed or spalled and brick delamination

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Figure 21.

West Side, Storage Room (looking to the south)

Figure 22.

West Side, Storage Room (looking to the north)

Figure 23.

West Side, Storage Room Note: Top flange of beam remaining

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Figure 24.

West Side, Storage Room Note: Remnants of beam on floor and web of supporting beam

Figure 25.

West Side, Storage Room – North End Note: Web of main beam is corroded through

Figure 26.

West Side, Storage Room – Access to street

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Figure 27.

West Side, Storage room – straight board forming left in place

Figure 28.

Air vent at side walk, typical

Figure 29.

East Side, Cracked slab and waste pipe

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Figure 30.

East Side, Cracked Slab at Entryway

Figure 31.

East Side, Typical Vent

Figure 32.

East Side, Cracked and Patched Slab

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Recommendations We provide herein two options to make these necessary structural repairs and provide a brief summary of the issues and benefits for each. We also note that a contractor be retained to install wood shoring for the first six beams at the north end of the basement along Julian Ave. While this is not an imminent hazard, the shoring should be installed in a timely fashion until the repair work can be completed. Option 1 At the south and west sides, provide new support line along the line where the flat slab abuts the barrel arched slab. This consists of a post and beam steel frame supported on new foundations. The area between the top of the new beam and soffit of the existing framing and slabs would be filled with non-shrink grout or drypack, same as done with baseplates. The width of the new beam is such that the structurally significant web corrosion of the main sidewalk beams is encapsulated after steel treatment. Other localized repairs are also anticipated. A list of the repair scope is below.

1. Construct foundations and new structural frames prior to selective demo or any vibration-induced work is performed to the sidewalk slab (See Appendix A for conceptual scope).

a. This work will involve coordination of new footing and posts with the existing mechanical equipment and selective (quite limited) relocation of electrical conduit and pipe work.

b. The new foundations shall consist of shallow foundations of 3’-0” square and 12” deep at a bearing level of 3’ below existing grade.

c. The steel is likely to be brought through the single trap door street access. d. At probably three locations the critical web length of the main steel member is

corroded through (see Figure 25). This will require local steel replacement. e. Remove loose corrosion deposits off of existing steel with wire wheel. Coat steel with

corrosion inhibitor. Corrosion on top of top flange to remain in place. 2. The manhole access in the boiler room should be abandoned by concrete infill and building of

a concrete corbel of, say, 2’ by 2’ in plan and 1’ deep (See figure 11) 3. Remove abandoned wood and framing used as slab forms along the west side (Figure 27) 4. With coordination with local municipalities et al, unless otherwise noted remove and replace

the following items: a. Parking meters should be able to remain in place and a waterproof boot provided b. Street lights (total 2) and provide new steel corbel to support these off of the URM

wall c. Mail box (total 1) d. Garbage container e. Fire and water mains should be able to remain in place and a waterproof boot

provided f. Electrical, standpipes, and gas conduits/pipes should be able to remain in place and a

waterproof boot provided 5. Abandon air vents by installing metal deck soffit and infilling with non-shrink grout. 6. Provide new air circulation method for the entire basement. 7. Remove abandoned boiler tank and all other non-operating components directly beneath the

storage area to facilitate efficient construction. 8. Remove all foreign objects around Fire and Life Safety components (See Figure 15) 9. Where anchors supporting pipes and ducts are cut through concrete slab scabbling (see item

10), provide supplemental support with shallow embed anchor.

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10. Remove top 1/2” to 3/4” of concrete slab with scabbler. Provide epoxy binder preparation and fiber glass reinforcement (20 lb/cyd cloth) overlay. Top slab with membrane and finish, extending up and flashing wall per architectural details.

11. Along Wiese Street, locally remove damaged slab and provide new ledgers and reinforced concrete slab. Provide drill and grout dowels along four sides of the existing slab.

12. Provide sump pumps and drainage in all areas beneath sidewalk. 13. Locally remove dilapidated framing and drypack with concrete (Allow six locations of 2 square

feet each). 14. Prior to slab work, infill trap door opening with reinforced concrete supported by metal with

angle ledgers. 15. Repoint exterior brick finish and paint to seal 16. Replace failed window sills and flashings on the ground floor.

Option 2 The south and east sides could be completely removed and replaced with steel framing and concrete fill on metal deck. The east side appears to be localized sidewalk dilapidation, where the slab has cracked and sunken down. We recommend a local slab remove and replace occur, which would consists of 4 by 4 ledger angles supporting a metal deck with concrete fill. The concrete fill on both sides would be reinforced and dowelled into the adjacent existing brick and concrete substrates. This would significantly impact the shop operation and building function. All of the mechanical and electrical equipment in the basement would require temporary alternate sources while the duct and pipe work is removed during the slab construction.

We recommend Option 1 and a reasonable contingency be provided as there is a risk of unforeseen conditions. Further, we would recommend either a cost estimator substantiate the recommendation by comparing the cost of the two Options provided. Please contact me at 415-243-4091 so that we can arrange a time to meet and go over these findings.

Sincerely, ZFA STRUCTURAL ENGINEERS

Mark A. Moore, SE, LEEP AP Executive Principal Enclosures: Plan and details of as-is condition and proposed Option 1 work

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B C D E F G

1 1

2 2

3 3

4 4

5 5

15'-4" 14'-6" 15'-6" 15'-6" 16'-0"

20'-8

7/8

"20

'-1 1/8

"20

'-5"

21'-1"

82'-4

"

4'-0

"

WIESE STREET

16TH

STR

EET

JULIAN AVENUE

FOUNDATION AND SIDEWALKPERIMETER

(E) MAIN SIDEWALK BEAMAT 5' O.C.

A

15'-11"

65"X70" TRAP DOOR

TITLE / PROJECT NAME

SECTION ENGR / CKR DATE PAGEJOB#

ALTAMONT HOTEL

GROUND FLOOR PLAN SKO 08/25/11 111309

1/16" = 1'-0"1 Ground Level

NORTH

G

(E) 6" DEEP BEAM3xà FLANGE

(E) FLAT SLAB

EXTERIOR OF BUIDLING

(E) ~å" BEARING ƒ

(E) 12" DEEP BEAM

(E) PIER &FOUNDATION

CURB

16TH ST

5'-0" 10'-0"

3 1/2"

(E) URMRETAINING WALL

G

NON-SHRINK GROUT

C8x13.7 (TOT 2)W/ å" ƒ @ COLUMN

á"x8"x12" ƒ BETWEENCHANNELS @ 3'-0"

W8x13 GALV POST@ EVERY THIRD BEAM

3'-0"x3'-0" W/ #5 @ 8" EW

å" GALV BASE ƒW/ (6) ANCHORS

C12x25 CURB

16TH ST

~5"

3 1/2"

(E) 12" DEEP BEAM

SIDEWALK

1/4" = 1'-0"1 Section A-A (EXISTING)

TITLE / PROJECT NAME

SECTION ENGR / CKR DATE PAGEJOB#

ALTAMONT HOTEL

SECTIONS SKO 08/29/11 211309

1/4" = 1'-0"2 Section A-A (NEW)

1/2" = 1'-0"3 Section 1-1 (EXISTING)