S01. Amendment 02 - Beaver Creek Dam_Observations of Pool Response to Storms.pdf
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- Solicitation number
- 12FPC321B0003
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This document contains details regarding a federal solicitation for the rehabilitation of the Beaver Creek Dam located in Chester County, Pennsylvania. The United States Department of Agriculture Farm Production and Conservation Acquisition Division is seeking a contractor to rehabilitate the dam to meet state and federal dam safety criteria and maintain the originally planned level of flood protection. The scope of work includes armoring the auxiliary spillway exit channel and side slopes with roller compacted concrete, replacing the principal spillway riser structure, installing access to existing toe drains through the impact basin headwall, installing riprap wave protection on the upstream face of the dam, and re-grading an area adjacent to the downstream toe and installing a trench drain. The solicitation is set aside for small businesses with a NAICS code of 237990 and size standard of $39.5M. The period of performance is 501 calendar days from notice to proceed with an estimated contract value between $1M-$5M. Questions are due by February 1, 2021 and answers will be provided in an amendment by February 7, 2021.
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Beaver Creek Dam: Information on Pool Response to Rainfall Events
1/26/2021
Pool Response on December 25, 2020 to 2.2 inches of rain Since the pool was dewatered in September 2020, the most significant runoff event happened on 12/24/2020. The Beaver Creek watershed received approximately 2.2 inches of rain in 18 hours from the afternoon of 12/24/2020 into the early morning hours of 12/25/2020. The pool increased approximately
3.8 feet as a result of the runoff from this event. Note that the sluice gate was fully open for this event.
Flood Detention Pool at Beaver Creek Dam, Riser in center of photo, photo taken on 12/25/2020 at 7:40 am.
Daily pool elevations from March 2013 through December 2016 In March 2013, CCWRA installed an automated pool level monitor, and we have daily pool elevations from March 2013 through 2016. Please note that the level is measured each day at 8am, so it is not the peak water elevation for the day, just a reasonable reference elevation. As depicted on the attached hydrograph of the pool elevations, the pool was 2.4 ft above normal pool seven times between March 2013 and December 2014.
0.4
1.4
2.4
3.4
4.4
5.4
6.4
01/01/13 07/02/13 01/01/14 07/02/14 01/01/15 07/02/15 01/01/16 07/01/16 12/31/16
Fe e t ab o ve n o rm al p o o l
Water Elevation above normal pool (ft)
487 ft 489 ft 491 ft 493 ft Height above normal pool
Beaver Creek Dam: Information on Pool Response to Rainfall Events
1/26/2021
Chronology of Key Flood Events from 2003 to 2020 when Beaver Creek Dam had a sediment pool The table below are peak pool elevations when there was a permanent pool. The following pool elevations are from either key storm events, or from dates when CCWRA staff were onsite for routine site visits or routine maintenance tasks. CCWRA staff typically conduct storm surveillance at Beaver Creek Dam when we get significant rainfall (often over 3 or 4 inches).
During smaller rain events, the pool elevation will frequently raise up to a foot over normal pool (between the orange and green lines on the accompanying map). However, CCWRA staff are typically not onsite to record the pool elevation for these smaller rain events.
Date
Peak Pool Level
Feet above normal pool
Notes
9/15/2003 491’ 4.4’ Hurricanes Henri and Isabel
12/11/2003 492’ 5.4’
10/9/2005 495.3’ 8.7’ Nearly 9 inches over 2 days
6/28/2006 493.9’ 7.3’ 6.8 inches over 6 days (with 5 inches on 6/26)
4/16/2007 489’ 2.4’
4/15/2009 490.0’ 3.4’
3/13/2010 488.3’ 1.7’
10/1/2010 495.2’ 8.6’
3/11/2011 481.5’ 4.9’
8/29/2011 485.1’ 8.5’ Hurricane Irene (approx. 5 inches over 2 days)
9/7/2011 494.0’ 7.4’ Tropical Storm Lee (approx. 3.8 inches over 3 days)
9/24/2011 494’ 7.4’
10/23/2011 490.5’ 3.9’ Small rain events on 10/19 and 10/20
1/19/2012 487.9’ 1.3’ Series of small rain events on 1/16 and 1/17
10/29/2012 492.8’ 6.2’ Superstorm Sandy
1/13/2013 488.1’ 1.5’ Series of small rain events over 2 days
6/10/2013 488.9’ 2.3’ 3.8 inches over 6 days (with 1.6 inches on 6/10)
6/28/2013 491.6’ 5.0’ Approx. 3.7 inches in preceding 48 hours
8/13/2013 490.2’ 3.6’ Approx. 2.3 inches of rain
10/11/2013 490.6’ 4.0’ Series of small rain events over 4 days
11/27/2013 488.4’ 1.8’ Nearly 2 inches over 2 days
1/11/2014 488.0’ 1.4’ Approx. 1.1 inches of rain
3/13/2014 488.3’ 1.7’ Small rain event (less than 0.5 inches)
4/15/2014 490.5’ 3.9’ Approx. 2.4 inches of rain over 2 days
5/1/2014 499.5’ 12.9’ Approx. 7 inches over 16 hours on 4/30/2014
3/11/2015 489.7’ 3.1’ Approx. 0.75 inches of rain
2/4/2016 488.0’ 1.4’ Approx. 1.04 inches of rain
2/25/2016 490.3’ 3.7’ Approx. 3 inches of rain
8/13/2018 491.6’ 5.0’ Approx. 2.8 inches in 2 hours
8/4/2020 495.2 8.6’ Approx. 4.3 inches in 6 hours, TS Isaias
Elevations are referenced to NGVD1929 vertical datum.
Normal pool is 486.6’ NGVD1929.
File details come from the government source that posted it. Updated .