HomeMy WebLinkAboutFDP201800013 Certified Engineer's Report 2019-12-16Schnabel T 610.696.6066 / F 610.696.7771
E N G I N E E R I N G 3 Dickinson Drive, Suite 200 / Chadds Ford, PA 19317 schnabel-eng.com
December 16, 2019
Mr. Walter Harris IV
County of Albemarle
Facilities & Environmental Services Department
401 McIntire Road
Charlottesville, VA 22902-4596
Subject: Hollymead Lake Dam Spillway Improvements, Record Documents Transmittal,
Albemarle County, Virginia (County Contract No. 2019-08013-02) (Schnabel
Reference 15615008.01)
Dear Mr. Harris:
SCHNABEL ENGINEERING, LLC (Schnabel) is pleased to submit the Record Drawings and DCR 199-
100 Record Report for this project.
In accordance with our agreement dated May 10, 2017, we observed the critical construction activities
related to construction of the principal spillway riser, articulated concrete block armoring on the
downstream slope, spillway conduit repairs, and other miscellaneous construction at the dam site.
In addition, as required by 4VAC50-20-80 (Alteration Permits) of the Virginia Impounding Structure
Regulations, we hereby certify' that to the best of our judgment, knowledge, and belief, the impounding
structure and its appurtenances were altered in conformance with the plans, specifications, drawings, and
other requirements approved by the Virginia Soil and Water Conservation Board.
We understand that the County will sign, compile, and submit the attached Record Documents, a copy of
this letter and necessary attachments to DCR for final approval.
We appreciate the opportunity to be of service for this project. Please contact the undersigned if
clarification is needed for any aspect of this transmittal.
Sincerely,
SCHNABEL ENGINEERING, LLC
Jeremy R. Young, PE
Senior Associate
' Certify means to state or declare a professional opinion whose true properties cannot be known at the time such certification was
made, despite the appropriate professional evaluation. A professional's certification of conditions in no way relieves any other party
from meeting requirements imposed by contract or other means, including commonly accepted industry practices.
County of Albemarle
Hollymead Lake Dam Spillway Improvements
I11:WAiTdi
Attachments:
(1) DCR 199-100 Record Report
(2) Record Drawings
Distribution (by email)
County of Albemarle
Attn: Mr. Walter Harris
Attn: Mr. Greg Harper
Project 15615008.01 / December 16, 2019 Page 2 Schnabel Engineering, LLC
'O
Date Prepared:
P�WNRWW
DCR Prepared By:
Nrginia Department of Conservation &Recreation
December 4, 2019
Andrew C. Vasko
RECORD REPORT FOR VIRGINIA REGULATED IMPOUNDING STRUCTURES
Reference: Impounding Structures Regulations, 4VAC 50-20-10 et seq., including 4VAC 50-20-70 and 80, Virginia Soil and Water
Conservation Board
1.
Project Information:
a. Name of Impounding Structure:
b. Inventory Number: 003174
Other Name (if any):
Hollymead Lake Dam
c. Name of Reservoir: Hollymead Lake
d. Check one: ®Old Structure ❑New Structure
2. Location of Impounding Structure:
a. City or County: Albemarle County
b. Located 5,020 feet/miles upstream/downstream of Highway Number
c. Name of river or stream: Powell Creek
SR 1670 — Ashwood Road
d. Latitude: 38.11517N Longitude: 78.433785W
3. Ownership:
a. Owner's Name: County of Albemarle
If a corporation, name of representative: Greg Harper
b. Mailing Address: 401 McIntire Road, Charlottesville, VA 22902
c. Telephone: (Residential) (Business) (434) 296-5832 x 3410
d. Other means of communication: ghamergalbemarle.org
4. Construction/Alteration Design Report:
a. Design Report prepared by: Greg Harper
b. Design Report date: April 18, 2018
c. Check one: ❑Construction ® Alteration Permit #: 003174 Date Issued: May 21, 2018
5. Owner's Engineer:
a. Engineering Firm and Engineer: Schnabel Engineering, Jeremy R. Young, PE
b. Professional Engineer Virginia Number: 0402053988
c. Mailing Address: 3 Dickinson Drive, Suite 200, Chadds Ford, PA 19317
d. Telephone: (Business) 610-696-6066
6. Impounding Structure Data (Identify datum used for all elevations):
a. Type of material: earth ® concrete ❑ masonry ❑ Other:
b. Top of Impounding Structure Elevation
Design Configuration
Varies 440.210 446.0 Feet
(DCR199-100) (09/08) Page 1 of
c. Downstream Toe Elevation (Lowest)
d. Height of Impounding Structure
e. Crest Length (Exclusive of Spillway)
f. Crest Width
g. Upstream Slope (Horizontal to Vertical)
h. Downstream Slope (Horizontal to Vertical)
7. Reservoir Data
a. Maximum Capacity
b. Maximum Pool Elevation
c. Maximum Pool Surface Area
d. Normal Capacity
e. Normal Pool Elevation
f. Normal Pool Surface Area
g. Freeboard (to lowest crest elevation)
8. Spillway Data Type
a. Low Level Drain Slide Gate
396.8
Feet
43
Feet
300
Feet
50
Feet
3 H: 1
V
3 H: 1
V
Design Configuration
798
Acre-feet
445.6
Feet
47.7
Acres
226
Acre-feet
426.4
Feet
20
Acres
13.8
Feet
Construction Design Invert
Material Capacity Elevation
Stainless Steel 73 cfs 420.0 Feet
b. Principal Spillway Riser Reinforced Concrete 73 cfs 426.4 Feet
c. Emergency Spillway Pipe w/ anti vortex Reinforced Concrete 199 cfs 427.1 Feet
plate and trash rack
d. Briefly describe the low level drain and principal spillway, include dimensions, trash guards, and orientation of intake
and discharge to dam if looking downstream: The low level drain is located on the upstream face of the riser. It consists of
a slide gate that can be operated using a tumwheel on the top of the riser. The principal spillway riser consists of three weirs
(one on each side and one on the upstream face of the riser) all at EL 426.4. The weirs are each 3 ft in length. A trashrack is
Drovided at each side weir and a full height trashrack at the uostream face covers both the weir and low level gate.
e. Describe the emergency spillway to include dimensions and orientation to dam if looking downstream
a common 54" Dia. RCP conduit.
9. Watershed Data:
a. Drainage Area: 142 square miles
b. Type and Extent of Watershed Development: Suburban/commercial with woods and some
c. Time of Concentration: 1.72 (hours) Routing Procedure: HEC-HMS
d. Spillway Design Flood used (mark appropriate box):
X PMF, source 24-Hr PMP (32.2 inches) From Probable Maximum Precipitation Study of Virginia
(Applied Weather Associated, 2016)
PMF, source
100 Year, source
50 Year, source
Other, source
e. Design inflow Hydrograph: Volume: 2,051 acre-feet
Peak inflow: 7,143 cfs
Rainfall duration of design inflow hydrograph: 24 hours
f. Freeboard during passage of spillway design flood: N/A designed for Overtopping feet
10. Impounding Structure History:
a. Date construction completed:
b. Designed by: Unknown
c. Built by: Unknown
1974
Date:
Date: Unknown
(DCR199-100) (09/08) Page 2 of 5
d. Inspections by: Unknown Date: Unknown
e. Description of repairs: There was originally a 36" diameter CMP riser and 24" diameter CMP spillway conduit near right
abutment. At some point (unknown), the risers were abandoned but there is no documentation of the
methods used. The existing auxiliary spillway appears to have been installed in the late 1980s.
f. Has the impounding structure ever been overtopped? ❑ yes ® No
11. Operational Procedures: Provide a narrative describing the following impounding structure procedures:
a. Operation: The County of Albemarle operates the low level outlet on an as -needed basis. Refer to procedures described in
DCR Operation and Maintenance Certificate prepared by Albemarle County.
b. Maintenance: The County of Albemarle cuts the grass and corrects erosion issues. Refer to procedures described in DCR
Operations and Maintenance Certificate prepared by Albemarle County.
c. Filling: N/A
d. Emergency Action Plan Implementation: The County of Albemarle is responsible for performing routine surveillance and
Implementing the EAP as needed.
e. Structure Evaluation: The County inspects all structures for cracking, leakage, or deterioration on a regular basis. Refer to
Procedures described in DCR Operation and Maintenance Certificate prepared by Albemarle County.
12. Hydraulic/Hydrologic Data: Provide a narrative describing the following hydraulic/hydrologic data:
a. Spillway Design Flood: PMF, obtained from VA 2015 PMP study
b. Hydrologic records: None
c. Flood experience: The embankment has not overtopped.
d. Flood potential: The dam is categorized as a high hazard structure.
e. Reservoir regulation: The County has the ability to control the reservoir level by opening/closing the low level slide gate.
f. Comments/ Recommendations: New riser and outlet basin constructed, Articulating Concrete Block overtopping protection
added to downstream slope, and spillway conduits repaired in 2019.
(DCR199-100) (09/08) Page 3 of
13. Dam Stability: Provide a narrative and evaluation describing impounding structure stability:
a. Foundation/abutments: Bedrock with a relatively thin layer (4 ft to 9 ft) of residuum.
b. Embankment materials: Embankment fill consists of both fine and coarse grained soils. Fine grained samples were
classified as lean clay, elastic silt, and silt. Consistency of the soils was stiff to very stiff. Coarse grained samples were
classified as silty sand. A slope stability analysis was performed using Geostudio software. The resulting factors of safety
were each above the minimum factors of safety required by USACE guidance for appropriate load cases.
14. Attachments:
a. Attach Record Drawings signed and sealed by a licensed professional engineer and signed by the owner.
(DCR199-100) (09/08) Page 4 of 5
CERTIFICATION BY OWNER'S ENGINEER
I hereby certify that the information provided in this Record Report and the attached Record Drawings have been examined by me
and found to be true and correct in my professional judgment.
Signed:
Signature Print Name
This 16th day of December 120 19
Engineer's Virginia Seal:
Certify means to state or declare a
professional opinion of conditions whose
true properties cannot be known at the
time such certification was made, despite
appropriate professional evaluation. A
professional's certification of conditions in
no way relieves any other party from
meeting requirements imposed by contract
or other means, including commonly
accepted industry practices.
Virginia Number. VA PE 0402053988
ww�A TH OF Dr
r�
JEREMY R. YOUNG Y
Lic. No. 0402053988
"01W,'O1VAL
BY OWNER
I hereby certify that the information provided in this Record Report and the attached Record Drawings have been examined by me.
Signed:
This 19th
Signature
day of June
20 20
Greg Harper
Print Name
Mail the executed form to the appropriate
Department of Conservation and Recreation
Division of Dam Safety and Floodplain Management
Regional Engineer
(DCR199-100) (09/08) Page 5 of