HomeMy WebLinkAbout12.04.19 Email from Mac Empleo and N. Chico Neighborhood Safety Group - N. Chico Land Use and Flooding Concerns
December 4, 2019
SENT VIA EMAIL (clerkoftheboard@buttecounty.net)
Chair Lambert and Board of Supervisor Members
Butte County Board of Supervisors
25 County Center Drive
Oroville, CA 95965
RE: North Chico Land Use and Flooding Concerns
Dear Chair Lambert and Board Members:
This firm represents the North Chico Neighborhood Safety Group. This group is
working to address issues in North Chico relating to flood hazards, new development
proposals that could worsen flooding, and other related concerns. In the past few months,
we have been gathering information to better understand the status of various issues
pertaining to existing and proposed land uses within the North Chico Specific Plan
and their associated environmental impacts including flood risk. Although our
research is ongoing, we have developed enough information to bring the concerns
discussed in this letter forward. The flooding that occurred in February 2019 was a major
precipitating factor in the need to update the Board and other County officials regarding
these issues. After heavy rains, Keefer Slough overtopped its banks and flooded the
streets of Autumn Park as well as areas downstream.
Water level at Garner Road bridge looking 4243 Anjou Court (2/27/19)
north (2/27/19)
Butte County Board of Supervisors
December 4, 2019
Page 2 of 12
The flooding events of February 2019 make clear that the County must take action
to address existing flood risks and avoid approving additional development that will
exacerbate existing flood risks. These flood risks are addressed in more detail in the
attached letter from MBK Engineers, who was asked to review flooding issues pertaining
to development in North Chico. (See Exhibit A.)
This letter includes:
A Discussion of the Factual Background regarding the North Chico Specific Plan;
A description of how proposed development in the NCSP would exacerbate flooding
and other environmental concerns;
An analysis of why new development must be analyzed in a single environmental
document; and
Requests for specific actions by County to address these concerns.
I. FACTUAL BACKGROUND
The Autumn Park Subdivision was constructed as part of the NCSP in the early
surface water runoff from the subdivision. That retention pond is located on a 1.49 acre
lot (APN 047-260-187), on the western side of Autumn Park that is owned by the
Nicolaus Family Trust, which is encumbered by a County easement to allow for the
construction and maintenance of a detention pond. The larger parcels to the west, north,
and southwest (around three sides of the Autumn Park Subdivision) is owned by farmer
and land developer George Nicolaus, and affiliated entities, such as ARCAPCO, Inc.
(APNs 047-260-199, 047-440-012, and 047-260-198).
Over the years, Mr. Nicolaus has endeavored to move forward on development of
his lands, which are currently in orchard use. For instance, in 2007, the County prepared
a Mitigated Negative Declaration for cancellation of Williamson Act
Contract for APN 047-260-199, the parcel immediately to the west of the Autumn Park
subdivision. This project was apparently never approved. Comments from Caltrans on
this project raised concerns with the exacerbation of flooding of Highway 99 from the
eventual development of this parcel, which would include raised building pads according
to the 2007 MND.
A. Actions by Mr. Nicolaus Exacerbated Flooding of Autumn Park
Unfortunately, Mr. Nicolaus has taken actions that worsen flood conditions in
Autumn Park and the greater region. For instance, in 2012, Mr. Nicolas planted a new
Butte County Board of Supervisors
December 4, 2019
Page 3 of 12
orchard in the area to the north of Autumn Park. In so doing, Mr. Nicolaus, leveled a
protective berm adjacent to neighboring property within Autumn Park to the south.
Newly planted orchard on APN 047-440-012, Google Earth Pro (5/2/2013)
When Keefer Slough overtopped its banks on February 14 and 27, 2019, the flood
waters overflowed to neighboring property. Water rushed through
orchard, and down the fire lane that borders Autumn Park, west of Garner Lane. From
the fire lane, water rushed down Bosc Drive to Magness and Anjou Courts. The retention
pond also filled and flooded back onto Anjou and Magness Courts. Flood waters came
within 15 feet of fronts doors, and were 4 feet deep.
Flood waters flowing down fire lane on south
Flood waters from Keefer Slough
side of Nicolaus orchard (2/27/2019)
flowing down Bosc Drive (2/14/19)
Mr. Nicolaus acted negligently when he laser leveled his orchard in 2012, which
included flattening a berm that previously protected neighboring property to the south
Butte County Board of Supervisors
December 4, 2019
Page 4 of 12
from flood damages. Private property owners are subject to traditional principles of
negligence when they make alterations to natural water channels or otherwise change the
flow of flood waters. (Ektelon v. City of San Diego (1988) 200 Cal.App.3d 804, 810
(Ektelon)
some protection to land owners making changes to protect themselves from flood waters,
it is not without limitation. (Id. at 809.) Further, no such protection would apply here as
Mr. Nicolaus was not attempting to protect his land from flood waters; rather, he
removed protections from such flood waters. Mr.
berm, whether inadvertent or purposeful, was unreasonable and negligent.
B. New Well Installations Have Not Been Properly Overseen
currently in
agricultural use within the NCSP have disregarded County requirements and procedures
applicable to groundwater wells. This disregard for basic groundwater permitting
requirements also raise serious long-term groundwater sustainability concerns. In
f Autumn Park retention pond is
likely to exacerbate flooding conditions.
An existing agricultural well at the corner of Garner Lane and Kittyhawk Drive,
which serves Mr. Nico
1
well permitting system. It appears that a permit was issued in 2017 to attempt to make
improvements to this existing well. Those improvements, however, were apparently
ineffective.
In September 2018, Mr. Nicolaus applied for a permit to drill a new well on APN
047-260-199, directly west of the Autumn Park subdivision and within the parcel for
which Mr. Nicolaus is now seeking to build 4 homes (discussed below). The application
indicates it would be for a Large Diameter Well, ostensibly for agricultural use. The
permit for this well was not granted because no flood elevation certificate was ever
provided, according to County .
1
The 2016 Municipal Service Review and Sphere of Influence Plan for CSA 172
(2016 MSR/SOI Plan) indicates that this well is the irrigation well serving CSA 172.
This information is incorrect, as the irrigation and fire suppression well for CSA 172 is
actually located in a fenced area at the north side of Kittyhawk Drive between Winesap
Court and Bosc Drive. Given the description in the 2016 MSR/SOI Plan, it appears that
Drive. That could explain the large increase in PG&E costs over the past few years,
subsequent to the planting of the orchard by Mr. Nicolaus.
Butte County Board of Supervisors
December 4, 2019
Page 5 of 12
In August 2019, Mr. Nicolaus submitted another well construction permit
2
application, this time slightly to the west, located at Kittyhawk Drive and Comice Court.
When personnel for Sullivan Drilling were asked what they were working on by a
permit application does not indicate the well type, although it was apparently processed
as a replacement well for the failed well at Kittyhawk Drive and Garner Lane. According
to County EHS staff, the well was built to specifications for a Public Water System,
confirming the statement of Sullivan Drilling personnel, but the well does not meet the
setback from septic tank requirements.
Note no box checked for well type in application
Construction in County right of way south of Kittyhawk
Drive for
Maintenance of the retention basin has been an ongoing concern, both before and
after the February 2019 flood events. Residents within Autumn Park subdivision have
exchanged numerous emails, numerous phone calls with County Public Works to inspect,
maintain and service the retention pond, yet nothing has been done. This belies common
sense given the flooding in February 2019.
2
Though the well application lists APN 047-260-198 as the location of the well, the
location is actually on a County parcel (APN 047-260-053).
Butte County Board of Supervisors
December 4, 2019
Page 6 of 12
In addition to failing to maintain the pond, the County has also allowed Mr.
Nicolaus to use the pond for purposes unrelated to the provision of drainage for Autumn
Park. Subsequent to completion of drilling the new 600 foot deep well in September and
October 2019, Mr. Nicolaus proceeded to pump large amounts of water from the well
into the Autumn Park subdivision retention pond. Despite the fact that the retention pond
does not serve any of the parcels owned by Mr. Nicolaus and his parcels
are not charged for services provided by CSA 172, the Assistant Public Works Director
3
.
CSA 172 Retention Pond filled with well water pumped by George Nicolaus (10/1/2019)
Subsequent to pumping water into the retention pond, in November 2019, the fact
4
that bentonite was part of the drilling solution was identified. Bentonite is a sealer and
would be expected to decrease the infiltration rate of water in the detention pond.
Subsequently, County Public Works advised that Mr. Nicolaus would scarify, or till the
bottom of the pond to increase the percolation performance. On November 25, 2019, Mr.
Nicolaus apparently undertook this work, without any engineering or other County
oversight. The top layer of the soil contaminated with bentonite was simply moved to the
sides and then scarified the bottom. Like the initial pumping, these actions were not
formally authorized.
3
Later, a
4
See http://wildlife.tamu.edu/files/2010/04/1_Sealing_Ponds.pdf,
https://sturgismaterials.com/products-view/sodium-bentonite/.
Butte County Board of Supervisors
December 4, 2019
Page 7 of 12
Grading in the Autumn Park retention pond on November 25, 2019
In any case, these actions within the retention basin do nothing to address known
flood issues from Keefer Slough. Clearly, Mr. Nicolaus should not be worsening the
functionality of the Autumn Park subdivision detention pond (see Ektelon, supra, 200
Cal.App.3d 804, 809-810), and County staff have failed to provide adequate maintenance
and with respect to well drilling and use of the
retention pond.
II. PROPOSED DEVELOPMENT PROPOSED IN THE NCSP WOULD
EXACERBATE FLOODING AND OTHER ENVIRONMENTAL
CONCERNS
A. Nicolaus Proposed Four Home Subdivision Application
Mr. Nicolaus submitted a four one-acre lot predevelopment application on
February 19, 2019 for APN is 047-260-199. It is directly north of the proposed Legacy
Village project (discussed below). (See Map, attached as Exhibit B.) Mr. Nicolaus has
requested that the tentative parcel map be processed as a separate application from
Legacy Village. It appears that the four homes would rely on the existing stormwater
detention basin in Lot 44, despite the fact that the County has determined that APN 047-
260-199 does not benefit from CSA 172. The decision to approve the project would be
As discussed in the MBK letter attached as Exhibit A, construction of these homes
could increase flood risks on nearby parcels, since they would be raised. As can be seen
in Exhibit B, the outdated flood map shows the Zone A flood line going through three of
the four proposed parcels. Given recent flooding events, it is a nonstarter for additional
drainage water being added to the community retention pond from these four houses.
Moreover, the County specifically identified APN is 047-260-199 as not benefitting from
Butte County Board of Supervisors
December 4, 2019
Page 8 of 12
CSA 172 facilities. Last, the proposed access from the existing subdivision would not be
compatible with existing development in Autumn Park.
B.
In October 2018, a predevelopment application to develop 100 clustered homes on
25 acres was submitted by Mr. Nicolaus. The Legacy Village project (previously called
Almond Ranch) would be located on APN 047-260-198, with density transfer from
. A golf course is also included in the plans. The golf
course and homes would be located in APN 047-260-198. (See attached Exhibit B.)
Drainage facilities are proposed to be located in the southernmost parcel. The application
states that a lot line adjustment, tentative subdivision map, and rezone will be needed.
County staff has indicated that an E) will be required
for this project. (See attached Exhibit B.) Traffic, flood and drainage have been
identified as key environmental issues by County staff.
Flooding
As discussed in the MBK letter attached as Exhibit A, development is constrained
by the flood zone shown in the Standard Digital Flood Insurance Rate Map
(Zone A in DFIRM). The existing DFIRM map product is not a precise indication of
actual flood flows, nor is it intended to be. Though the proposed development is mostly
aligned to avoid flood zone, with the homes proposed for the southeast corner of the
parcel, there is no detailed, up-to-date flood map for this area, and the flooding of
February 2019 showed that the mapped flood zone is incorrect.
In 2017, the Nord community was approved for State funding to conduct
feasibility study projects under the Small Communities Flood Risk Reduction Program.
There is insufficient information upon which to base any determination of the current
flood status of the area, or the effect of future development such as the Legacy Village.
A new model would be updated to reflect existing topography and development, as well
as storm event frequency. It is likely that the map will be different than the current
DFIRM map. Even with the homes proposed out of the flood zone identified in the
DFIRM map for insurance purposes, roads and other improvements associated with the
project would be within the floodplain and could significantly constrain flood flows.
These restrictions and the effect on regional flooding would need to be analyzed in an
EIR.
The 2016 LAFCo Municipal Services Review and Sphere of Influence report does
not adequately address drainage issues in this area. For instance, drainage into Keefer
Slough from the Pheasant Landing/Sierra Moon subdivision (CSA 169) is omitted. The
Butte County Board of Supervisors
December 4, 2019
Page 9 of 12
actual storm water drainage from this CSA of 140 homes is pumped into Keefer Slough
by two pumps, contributing to flooding of the Keefer Creek Estates subdivision, homes
off Dusty Lane, and Autumn Park Subdivision.
5
adequate infrastructure and flood protections improvements. The Sierra Moon
development did not install adequate retention ponds; thus, stormwater runoff from these
homes is diverted directly into Keefer Slough. More homes in this subdivision are being
built every day.
In addition, many other homes built off both sides of Keefer Road over to
Highway 99 and the Garner Lane homes are not a part of a CSA. These homes are also
annually flooded in their neighborhoods. Keefer Slough cannot accommodate drainage
from existing development, let alone future development such as the Four Parcel
Subdivision and Legacy Village projects proposed by Mr. Nicolaus.
On November 5, 2019, the Board of Supervisors unanimously passed item 4.04
North Chico Flood Plan, where the Board acknowledged the flood problems in North
Chico and adopted a resolution that requires the Planning Division to notify developers
and prospective homeowners that it floods in North Chico. This is an important step
forward, but more action and leadership is necessary given the severe flood risks posed.
Unfortunately, the Resolution fails to reference existing County requirement for
new development that the site be reasonably safe from flooding. (MBK Letter, Exhibit
A, pp. 5-6, Butte County Code, § 26-23.) In its review,
the County must take into consideration that the existing FEMA Zone A
maps are outdated and are not accurate, based on the flooding that occurred
in February 2019. As per Section 26-23(a)(2), the County must require the
developer to prepare a cumulative hydraulic impact analysis to demonstrate
that the proposed developments do not increase the water surface elevation
on neighboring properties.
(Id. at p. 6.) Thus, in addition to warning developers and permit applicants, the County
must also responsibly assess incremental flood risks posed by new development and
make sure the development does not increase flood base elevations on neighboring
5
Sierra Moon hat is failing and is causing
wells to be contaminated. This same sewer package facility is slated to be used in the
Legacy Village development, causing additional concerns.
Butte County Board of Supervisors
December 4, 2019
Page 10 of 12
property. We know from flooding in February 2019 that this duty has not been carried
out, and that new pending development proposals will only make conditions worse.
Groundwater
The project description in the predevelopment application states the project would
groundwater use would be consistent with the requirements of the Sustainable
6
From
Nicolaus, groundwater is only available in the deep aquifer. To the extent Mr. Nicolaus
intends to rely on the new well assumed to replace the agricultural well on the corner of
Garner Lane and Kittyhawk Drive, it cannot meet the setback from septic requirements
for a Public Water System.
Wastewater Treatment
The Legacy Village project would rely on a package Waste Water Treatment
WWT plant. It is unclear where the waste water would discharge. Combined with
the flooding issues, winter-time wastewater disposal could be a serious problem. This
has been an ongoing issue in the Sierra Moon subdivision, for instance, where the
package WWT is not functioning properly.
Traffic
Traffic issues and traffic congestion in North Chico continues to worsen, and
would be exacerbated by the Legacy Village project. If housing continues to be approved
in North Chico, issues to be addressed include mitigation for traffic congestion, delayed
safety response times, and flooded evacuation routes. There are currently no mitigation
plans for these serious traffic issues.
III. SEPARATE ENVIRONMENTAL REVIEW OF THE FOUR PARCEL
SUBDIVISION AND LEGACY VILLAGE WOULD CONSTITUTE
UNLAWFUL PIECEMEALING
Mr. Nicolaus has requested that the County analyze the environmental effects of
the two adjacent development projects separately. This would constitute impermissible
piecemealing. Piecemealing or segmenting means dividing a project into two or more
6
See https://www.buttecounty.net/waterresourceconservation/Sustainable-
Groundwater-Management-Act/Butte-County-Subbasins/Vina.
Butte County Board of Supervisors
December 4, 2019
Page 11 of 12
pieces and evaluating each piece in a separate environmental document, rather than
evaluating the whole of the project in one environmental document. This is explicitly
forbidden by CEQA, because dividing a project into a number of pieces would allow a
Lead Agency to minimize the apparent environmental impacts of a project by evaluating
individual pieces separately, each of which may have a less-than- significant impact on
the environment, but which together may result in a significant impact. Segmenting a
project may also hinder developing comprehensive mitigation strategies.
Given the intertwined environmental impacts associated with the proposed Four
Parcel Subdivision and the Legacy Village project, they must be analyzed together in a
single EIR. Under CEQA, the whole of the action must be considered and that the
The
piecemealing or segmenting issue is also de novo. (Communities for a Better
Environment v. City of Richmond (2010) 184 Cal.App.4th 70, 98.)
The County has been aware for decades that there is a flooding issue in North
Chico yet has continued to approve new developments without adequate attention to
flood control. In addition to flooding, groundwater and traffic impacts necessitate review
of these North Chico development projects in a single EIR. Continuing to approve
housing projects without adequate drainage and flooding facilities imperils existing
communities. Interim fixes implemented by the County, Rock Creek Reclamation
District and others are only temporary, one season fixes; a comprehensive solution is
needed.
* * *
The North Chico Neighborhood Safety Group requests that the Board of
Supervisors adopt a moratorium on all development within the NCSP area until flooding,
infrastructure, and safety concerns are addressed.
updated to address the current drainage conditions in North Chico, including the
overreliance on Keefer Slough. If any new development is to proceed, it must only do so
in full compliance with existing flood and safety requirements, including a showing that
flood elevations will not increase, in addition to compliance with other environmental
laws. The County must also provide proper oversight over CSA facilities, and not allow
them to be managed or damaged by unauthorized parties not designated as beneficiaries.
Last, environmental review of new development projects in the NCSP must not be
segmented and must fully address and mitigate flooding impacts.
Butte County Board of Supervisors
December 4, 2019
Page 12 of 12
Please feel free to contact me with any questions about the information contained
in this letter.
Very truly yours,
SOLURI MESERVE
A Law Corporation
By:
Osha R. Meserve
ORM/mre
Attachments:
Exhibit A
Exhibit B, Map of Nicolaus Legacy Village and 4 Home Subdivision Proposal
cc (via email):
Butte County Board of Supervisors:
Bill Connelly, bconnelly@buttecounty.net
Debra Lucero, dlucero@buttecounty.net
Tami Ritter, tritter@buttecounty.net
Steve Lambert, district4@buttecounty.net
Doug Teeter, dteeter@buttecounty.net
Butte County Planning Commissioners:
District 1, Michael Evans, oneniceplace@hotmail.com
District 2, Vice Chair Peter Hansen, pzhbuttecounty@gmail.com
District 3, Second Vice Chair Henry Schleiger, schleiger.bcpc@gmail.com
District 4, Chair Rocky (Daniel) Donati, rockdonati@aol.com
District 5, Ruby Roethler, rroethler@digitalpath.net
Public Works Director Dennis Schmidt, publicworksdept@buttecounty.net
Public Works Assistant Director Radley Ott, ROtt@buttecounty.net
Environmental Health Director Elaine McSpadden, emcspadden@buttecounty.net
County Counsel Bruce S. Alpert, balpert@buttecounty.net
Deputy County Counsel Brunella M. Wood, bwood@buttecounty.net
Butte County LAFCo Director, Steve Lucas, slucas@buttecounty.net
EXHIBIT A
WaterResourcesFloodControl WaterRights
G
ILBERT C OSIO, J R., P.E. A NGUS N ORMAN M URRAY
M ARC V AN C AMP, P.E. 1913-1985
W ALTER B OUREZ, III, P.E.
R IC R EINHARDT, P.E.
D ON T RIEU, P.E. C ONSULTANTS:
D
ARREN C ORDOVA, P.E. J OSEPH I. B URNS, P.E.
N ATHAN H ERSHEY, P.E., P.L.S. D ONALD E. K IENLEN, P.E.
L EE G. B ERGFELD, P.E.
B
EN T USTISON, P.E.
T HOMAS E NGLER, P.E., CFM
M ICHAEL M ONCRIEF, P.E.
November 27, 2019
Sent Via Electronic Transmittal
Osha Meserve
Soluri Meserve
th
510 8Street
Sacramento, CA 95814
Subject: Flood Comments on Proposed North Chico Specific Plan
Development Projects
Dear Ms. Meserve:
George Nicolaus and other affiliated entities are proposing two housing developments
near the Autumn Park Subdivision, north of the City of Chico and within the North Chico
Specific Plan. These two housing developments are located near or within a Federal Emergency
Management Agency (FEMA) Zone A and in an area which has historically flooded. These two
housing developments have the potential to:
1.Put additional residences/homes in a flood hazard zone.
2.Exacerbate flooding in surrounding parcels.
MBK Engineers (MBK) has compiled and reviewed existing reports, studies, photos and
videos, maps, ordinances, etc., to help better inform local, state, and federal agencies the
1
potential flood hazard in this area and has summarized key findings and comments below.
Proposed Development
The proposed developments are to the west and south west of the Autumn Park Subdivision. The
first development is located on a 52.5 acre parcel (APN 047-260-199) of the subdivision.
The proposal is to sub-divide the western portion of the parcel into four 1 acre lots (Figure 1).
1
Attached is Exhibit 1 showing my qualifications and experience to review and comment on
flood issues.
455 University Ave. Suite 100 Sacramento, California 95825 Phone: (916) 456-4400 Fax: (916) 456-0253 Website: www.mbkengineers.com
Osha MeserveNovember 27, 2019
Flood Comments on Proposed North Chico Specific Plan Development ProjectsPage 2
Figure 1. Western Portion of the Parcel Divided in Four 1-acre lots
The second development (Legacy Village, a.k.a. Almond Ranch) is located southwest of the
subdivision near the projected intersection of Kittyhawk Drive and Highway 99. The proposed
development is on a 51 acre parcel (APN-047-260-198) with plans for 100 clustered residential
lots and a nine-hole golf course with associated facilities (Figure 2). The proposed housing
density is about 5 units/acre.
Figure 2. Proposed Development
Osha MeserveNovember 27, 2019
Flood Comments on Proposed North Chico Specific Plan Development ProjectsPage 3
FEMA Flood Hazard Zone
The two proposed developments are in or near a FEMA Zone A (see Figure 3). A FEMA Zone A
is defined as “Areas subject to inundation by the 1-percent annual chance flood event generally
determined using approximate methodologies. Because detailed hydraulic analyses have not
been performed, no Base Flood Elevations (BFEs) or flood depths are shown. Mandatory flood
insurance purchase requirements and floodplain management standards apply.”
The FEMA Zone A for Keefer Slough was developed in April 2000 as part of a county wide
effort to investigate the existence and severity of flood hazards. To determine flood hazards,
hydrologic and hydraulic analysis was performed which:
1.Quantifies the flows in the river/slough.
2. Computes or estimates the water surface elevations in the river and floodplain
associated with the 1% chance annual flood (100-year flood).
Figure 3. Location of the Two Proposed Developments
Hydrologic Analysis
The April 2000 hydrologic analysis estimated the 100-year flood event for Rock Creek and
Keefer Slough. Rainfall-runoff models were developed using software developed by USACE
Hydrologic Engineering Center (HEC). HEC-1 was the computer model used in the April 2000
hydrologic analysis. This computer model used 30 years of recorded precipitation data from the
City of Chico and physical parameters of the Rock Creek/Keefer Slough dating back to a
USACE 1975 study.
A key assumption in the hydrologic model is the determination of how much of the Rock Creek
total flow gets diverted into Keefer Slough. For the April 2000 analysis, a rating curve was
Osha Meserve November 27, 2019
Flood Comments on Proposed North Chico Specific Plan Development ProjectsPage 4
developed using normal depthcalculations using typical cross sections/topography at the Rock
Creek and Keefer Slough flow split. It was estimated that approximately 44% of the Rock Creek
100-year flow is diverted into Keefer Slough.
Table 1 below shows the estimated 1% annual peak flows along Keefer Slough used in the April
2000 analysis.
Table 1. Estimated 1% Annual Peak Flows used in April 2000 Analysis
Location100-Year Flood Peak Discharge (cfs)
Keefer Slough approximately 1125 ft downstream of
560
Hicks Lane
Keefer Slough approximately 500 feet upstream of
680
Garner Lane
Keefer Slough at State Highway 99525
Source: FEMA (2011)
Hydraulic Analysis
The hydraulic analysis to develop the FEMA Zone A shown on Figure 3 was also performed in
April 2000. A hydraulic analysis typically requires a discharge rate, topography, and parameters
associated with vegetation within the river/slough. The April 2000 hydraulic analysis utilized the
computer model HEC-2, developed by the U.S. Army Corps of Engineers (USACE). Ground
elevations of Keefer Slough and surrounding floodplains were obtained from U. S. Geological
Survey (USGS) 7.5 minute quadrangle maps.
Flooding Dynamics/Historic Flooding
The Autumn Park Subdivision and surrounding parcels are located within the south overbank of
Keefer Slough. During periods of extreme flow rates on Keefer Slough, water will overtop its
bank and flow in a southwesterly direction, overtop Highway 99, and continue to flow towards
the town of Nord. Butte County has documented flooding in January 1995, March 1995, January
1997, and February 1998 (Butte County Supervisor Agenda Item 4.05, January 8, 2013). Other
years that this area experienced flooding include 1969, 1970, 1973, 1974, 1978, 1982,and 1983.
The cause of the flooding in the Rock Creek/Keefer Slough system has been attributed to:
1. Insufficient channel capacity in Rock Creek and Keefer Slough for flows produced by the
watershed size and slope (USACE,2008).
2. Leveling of fields (California Department of Water Resources \[DWR\], 2014).
3.Private levees (DWR,2014).
4. Sedimentation at the Rock Creek-Keefer Slough flow split (DWR, 2014; USACE, 2008;
FEMA,2011).
Most recently, this area flooded in February 2019. Exhibit 2 shows pictures of flooding in the
Autumn Park Subdivision. Keefer Slough overtopped its banks downstream of Garner Road then
flowed in a southwesterly direction through the streets of Autumn Park Subdivision then
continued to sheet flow towards Highway 99 ponding against overtopping the highway causing
closure of the highway. There was widespread media coverage of flooding in February 2019:
Osha Meserve November 27, 2019
Flood Comments on Proposed North Chico Specific Plan Development ProjectsPage 5
https://www.chicoer.com/2019/04/12/north-chico-flooding-focus-of-listening-session/
https://www.chicoer.com/2019/04/17/north-chico-resident-irate-over-flooding-issues/
https://krcrtv.com/news/butte-county/county-finds-temporary-fix-for-keefer-slough-flooding-
nord-more-troublesome
https://krcrtv.com/news/butte-county/sandbag-barrier-put-up-to-protect-se-chico-subdivision-
from-flooding
https://www.actionnewsnow.com/content/video/506412552.html
https://kpay.com/kpay-news/archives/2019-02/
https://twitter.com/CALFIRE_ButteCo/status/1101536680916336641
Of particular note, the FEMA Zone A map does not show flooding within the Autumn Park
Subdivision. However, Exhibit 2 clearly shows streets and yards being flooded.
Technical Flood Comments
1. The existing FEMA Firm Maps for the area are not detailed flood zones and are based on
outdated hydrologic and hydraulic analysis and underlying data. The hydrologic and
hydraulic models (HEC-1 and HEC-2) are legacy models dating back to the 1980s and
1990s. The HEC-2 model is a simplified standard-step backwater calculation of water
surface elevation, and cannot accurately simulate the shallow overland flow that actually
occurs in the Rock Creek/Keefer Slough floodplain. The topography used in the HEC-2
model dates back to 1951, and has an accuracy of plus or minus 2.5 feet.
2. The FEMA Zone A along Keefer Slough is based on a 100-year flow rate of 560-680 cfs.
This flow rate is based on a rating curve which approximated a total of 41% of the total
Rock Creek flow being diverted into Keefer Slough. This rating curve was based on
USGS quadrangles dating back to 1951. As noted by USACE and DWR, this area has
experienced significant sediment deposition, which has the potential to send more flood
waters down Keefer Slough. The use of a rating curve to estimate the flow rate in Keefer
Slough is not accurate and is not reflective of the actual site conditions today. This may
result in flooding in areas not delineated by the FEMA FIRM Maps.
3.The Legacy Village planned development and the four lots shown in Figure 1 has lots at
the edge of the FEMA Zone A. The FEMA Zone A is an estimated delineation of the
flood hazard and is not accurate and outdated based on comments 1 and 2 above. DWR
acknowledges that the existing FEMA FIRM maps are outdated and is currently working
through a Co-operative Technical Partnership with FEMA to revise the FEMA FIRM
maps in the Rock-Keefer Slough areas (as per a teleconference with Todd Hillare).
4. In the County’s review of these two proposed development projects, the County must
follow Butte County Code 26-23, cited below. Section 26-23(a)(1) requires the County to
Osha Meserve November 27, 2019
Flood Comments on Proposed North Chico Specific Plan Development ProjectsPage 6
determine that the site is reasonably safe from flooding. In its review, as per this section,
the County must take into consideration that the existing FEMA Zone A maps are
outdated and are not accurate, based on the flooding that occurred in February 2019.
As per Section 26-23(a)(2) the County must require the developer to prepare a
cumulative hydraulic impact analysis to demonstrate that the proposed developments do
not increase the water surface elevation on neighboring properties.
26-23 - Review of development permit applications—Generally.
(a)The Department of Development Services and Department of Public Works shall
review all development permit applications to determine that:(1)The site of the proposed
development is reasonably safe from flooding;(2)All necessary permits have been
received as required by federal or state law;(3)The proposed development does not
adversely affect the carrying capacity of areas where base flood elevations have been
determined but a floodway has not been designed. For purposes of this article, "adversely
affects" means that the cumulative effect of the proposed development when combined
with all other existing and anticipated development will increase the water surface
elevation on neighboring properties. The county will not allow development to increase
the water surface elevation of the base flood more than one (1) foot at any point, nor will
it allow any increase in the base flood elevation which adversely affects any neighboring
property.
5. The four proposed lots shown in Figure 1 are within a FEMA Zone A. As per Butte
County Code 26-24(b)(3). The applicant must determine the FEMA BFE in accordance
using detailed hydrologic and hydraulic analysis.
26-24(b)(3) In an A Zone, without BFE's specified on the FIRM (unnumbered A Zone),
all structures, residential and nonresidential, shall be elevated at least one (1) foot above
the BFE as determined by methods comparable to those in a Flood Insurance Study or by
using the detailed methods as described in the most current edition of FEMA publication,
FEMA 265, "Managing Floodplain Development in Approximate Zone A Areas—A Guide
for Obtaining and Developing Base (100-year) Flood Elevations" or any successor
FEMA document.
References
1. (DWR, 2014). Mid and Upper Sacramento River Regional Flood Management Plan.
November 10, 2014.
2. (FEMA, 2011). Flood Insurance Study, Butte County California and Incorporated Areas,
Federal Emergency Management Agency.January 6, 2011.
3. (USACE,2008). Rock Creek-Keefer Slough, Butte County CA, 905(b) Reconnaissance
Report. September 2008.
Osha Meserve November 27, 2019
Flood Comments on Proposed North Chico Specific Plan Development ProjectsPage 7
If you have any questions or require additional information, please call or email me.
Sincerely,
MBK ENGINEERS
Don Trieu, P.E.
DT/oh
R:8888.9/Flood Comments on Proposed Development 11-25-2019
Enclosures:Exhibit 1. Qualifications and Experience
Exhibit 2. Autumn Park Subdivision Photos
EXHIBIT 1
D ON T RIEU
EDUCATION
California State University, Sacramento
BS in Civil Engineering, 1995
California State University, Sacramento
MS in Civil Engineering, 2002
PROFESSIONAL LICENSES &SOCIETIES
Registered Civil Engineer, California No. C058284
Member, American Society of Civil Engineers
EXPERIENCE
1995 to Present MBK Engineers, Sacramento, CA
Principal
Principal Engineer in charge of hydraulic/hydrologic models for evaluation of flood control alternatives and
development of design water surface elevation. Perform hydraulic/hydrologic analysis of flood problems and
evaluation of flood control alternatives using HEC-RAS, RMA-2, FLO-2D, UNET, HEC-1.
EXPERIENCE HIGHLIGHTS
Technical adviser, hydraulic model development, and 200-year floodplain mapping for the lower San
Joaquin River Flood Control Project and Stockton urban area streams in support of DWR’s Central
Valley Floodplain Evaluation and Delineation Program (2008-2013).
Formulation, oversight and review of hydraulic analysis in support of alternatives evaluation and
hydraulic impact analysis for widen of the Sacramento Weir (2019).
Hydraulic model development and re-calibration of a SRFCP hydraulic model in support of USACE
WRDA 2016 projects.
Develop 2D model and hydraulic analysis of the Yuba River Goldfields in support of a new levee south
of the Yuba River Goldfields (2017-2019).
Reconnaissance level hydraulic impact analysis in support of alternatives formulation for Little Egbert
Tract Multi-Objective Project (2017).
Prepare cumulative hydraulic impact analysis in support of Lower Sacramento River/Delta North
regional flood control components (2017).
Update hydraulic model of the North Delta region in support of the McCormack-Williamson Tract Levee
Modification and Habitat Development Project and Sacramento County Point Pleasant FEMA Base
Flood Elevation Study.
Developed 2D model of the lower San Joaquin River and tributaries in support of hydraulic impact
analysis of 1700 acres of habitat restoration at Dos Rios Ranch (2017).
Principal in charge of hydraulic analysis for the Lower Feather River Corridor Management Plan.
Evaluate hydraulic impacts of wetland restoration project on Cougar Wetlands using the North Delta
HEC-RAS model.
Evaluate hydraulic impacts using the North Delta HEC-RAS for the Cosumnes Mitigation Bank.
Evaluate hydraulic impact using RMA-2 for Liberty Island Conservation Bank on the Yolo Bypass.
Technical adviser for development of RMA-2 model of the Sutter Bypass for evaluation of vegetation
management.
EXHIBIT 2
Osha Meserve November 27, 2019
Exhibit 2Page 1
Photo No. 1. Flood waters from Keefer Slough Flowing down Bosc Drive (2/14/19)
Osha Meserve November 27, 2019
Exhibit 2Page 2
Photo No. 2. Flooding of Fire Lane between Orchard and Northern Boundary of Autumn Park (2/27/19)
Photo No. 3. 4243 Anjou Court (2/27/19)
Osha MeserveNovember 27, 2019
Exhibit 2Page 3
Photo No. 4. 4243 Anjou Court (2/27/19)
Photo No. 5. 4231 Anjou Court (2/27/19)
Osha Meserve November 27, 2019
Exhibit 2Page 4
Photo No. 6. 4231 Anjou Court (2/27/19)
Osha Meserve November 27, 2019
Exhibit 2Page 5
Photo No. 7. 4231 Anjou Court (2/27/19)
Photo No. 8. Water level at Garner Road Bridge looking North (2/27/19)
Osha Meserve November 27, 2019
Exhibit 2Page 6
Photo No. 9. Looking west from Garner Road Bridge down Keefer Slough (2/27/19)
Photo No. 10. East End of Orchard where Water Flowed into Orchard; Garner Road Bridge in background (2/27/19)
Osha Meserve November 27, 2019
Exhibit 2Page 7
Photo No. 11. Water in Nicolaus Orchard (2/27/19)
Photo No. 12. Water being Pumped from CSA-172 Retention Pond back into Keefer Slough (3/3/19)
Osha Meserve November 27, 2019
Exhibit 2Page 8
Photo No. 13. Sand Bags being Installed in Nicolaus' Orchard bordering Keefer Slough (early March 2019)
Osha Meserve November 27, 2019
Exhibit 2Page 9
Photo No. 14. Sand Bags on Nicolaus' Orchard bordering Keefer Slough (early March 2019)
EXHIBIT B
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