Court Opinion

ID: 9383655
Source: CourtListenerOpinion
Date Created: 2023-03-30 21:03:31.380399+00
Date Added: 2024-06-11T17:17:47.261829
License: Public Domain

Filed 3/30/23
                      CERTIFIED FOR PUBLICATION

       IN THE COURT OF APPEAL OF THE STATE OF CALIFORNIA

                         FIRST APPELLATE DISTRICT

                                 DIVISION TWO

 BRIAN SHENSON et al.,
         Plaintiffs and Appellants,           A164045

 v.                                           (Contra Costa County
 COUNTY OF CONTRA COSTA et                    Super. Ct. No. CIVMSC1701267)
 al.,
         Defendants and Respondents.

       Plaintiffs and appellants (collectively, Owners) are two couples who
purchased residential properties in neighboring subdivisions within Contra
Costa County (County) in 2010 and 2016. Both properties are adjacent to a
creek. They sued the County and a flood control district (collectively,
Government Entities) for inverse condemnation and parallel tort causes of
action after drainage improvements the subdivision developers had
constructed 40-plus years earlier failed and serious erosion and subsidence
damaged Owners’ properties. Owners appeal from the judgment the superior
court entered after granting summary judgment against them on their
complaint.
       The parties litigated the case for about four years, completing all or
most discovery. The Government Entities filed motions for summary
judgment or in the alternative summary adjudication. The material facts are
undisputed. In substance, in the mid-1970s, the County approved

                                        1
subdivision maps for two subdivisions containing the parcels later acquired
by Owners. The creek that runs along Owners’ properties is a natural
watercourse that functions as the main receptacle for storm runoff emanating
from the watershed above Owners’ properties and is the only reasonable
means of collecting and conveying that runoff. Pursuant to the Subdivision
Map Act, the County required the developers to make certain drainage
improvements to collect and convey water from the two subject subdivisions
as well as one adjacent subdivision, to the creek. Among the properties that
contribute runoff to the creek by way of the improvements were three roads,
two private roads serving as ingress and egress to the subdivisions and one
county owned road that is adjacent to one of the subdivisions.
      As provided by the Subdivision Map Act, the County also required the
subdivision developers to dedicate drainage easements to the County. When
it approved the subdivision maps, however, the County did not accept the
offers of dedication for the drainage improvements, which remained in the
ownership of the developers and later the homeowners who purchased the
property.
      Owners claim the County assumed ownership and responsibility for the
drainage improvements by requiring the subdivision developers to construct
them and to offer to dedicate easements to the County to enable it to
maintain them. The County contends that it did not accept the offers to
dedicate the easements and did not otherwise assume responsibility for
maintaining them.
      Owners sued the flood control district under inverse condemnation and
other theories, positing that its collection of drainage fees from homeowners
in subdivisions within the watershed rendered it responsible for the drainage
improvements constructed by the subdivision developers. The evidence

                                      2
indicates the district did not fund those improvements, which preceded its
formation. It contends it cannot be liable for merely collecting fees for future
improvements that, thus far, have not been constructed because of the
unavailability of matching federal funds.
      We affirm the judgment. As a matter of law, a public entity must
either own or exercise actual control over a waterway or drainage
improvements to render them public works for which the public entity is
responsible. The undisputed facts here do not establish any such ownership
or control.
                               BACKGROUND
                                       I.
                                     Facts
      In the 1970s and 1980s, the County approved subdivision maps for
minor subdivisions in then-unincorporated parts of the County. As relevant
here, the County approved the developer’s application for a subdivision map
for Minor Subdivision (MS) 102-72 in 1973, subject to various conditions. It
approved the application for Subdivision 4983 in 1980, again apparently
subject to conditions.
      Both subdivisions were bordered on one side by a tributary of a creek
known as “Murderer’s Creek.” As the parties have done, for ease of reference
we will refer to the tributary as “Murderer’s Creek” or “the Creek.” The
Creek is a natural watercourse that has functioned historically as the main
receptacle for storm water runoff emanating from the watershed upstream of
these subdivisions. When the applications for the subdivision maps for
subdivisions MS 102-72 and 4983 were made, the County imposed certain
conditions relating to drainage.

                                       3
      One condition for approval of the MS 102-72 subdivision map was that
the subdivision developer “construct, install and complete . . . tract drainage”
and conduct related work and improvements “in a good, workmanlike
manner. In accordance with accepted construction practices and in a manner
equal or superior to the requirements of the County Ordinance Code and
rulings made thereunder . . . .” The developer was required by county
ordinance to collect and convey “[a]ll surface waters flowing from the
subdivision in any form or manner” from the development to the nearest
natural watercourse with a definable bed and banks or to a public storm
drainage facility. The developer of MS 102-72 was required, among other
things, to improve the channel of the Creek “to convey the peak design runoff
for the watershed” and to provide drainage of runoff from a private cul-de-sac
within the subdivision known as “Kelly Ann Court” via a conduit to the
Creek.
      Some of the other drainage improvements the developer constructed
and installed were an outfall at the Creek with a spillway to protect the bed
and bank of the Creek against erosion from the accelerated discharge of
surface water from the pipeline into the Creek, sidewalks, curbs, and gutters
on Gloria Terrace, a County road adjacent to the subdivision, and a means of
diverting and conveying surface water accumulating on that road through
MS 102-72 to the discharge point at the Creek. At some point during the
subdivision process, the County requested the developer’s cooperation in
obtaining an easement within MS 102-72 for the purpose of installing a drain
line to complete public improvements benefiting a neighboring subdivision
(Subdivision 4234). MS 102-72 improvement plans submitted to the County
included the “buried storm drain line” running along the western limit of the
subdivision where it adjoined Subdivision 4234, which received runoff from

                                       4
that subdivision, merged with runoff from MS 102-72 in a catch basin and
was conveyed through an underground pipeline through MS 102-72 to the
Creek.
      The developers of MS 102-72 (and Subdivision 4234) designed and
constructed the improvements, not the County. However, a county ordinance
required developers to submit plans for required improvements to the
County’s Public Works Department for review and required the Department
to inspect the work and, when satisfied it was complete and met county
requirements, to recommend that the County Board of Supervisors accept the
improvements. The limited purpose of such acceptance was to establish an
end date for the contractor’s liability under a provision requiring it to
guarantee performance of the work and repair of defects for a one-year period
after acceptance.
      The Board by resolution accepted the improvements for MS 102-72 as
“completed for the purpose of establishing a terminal period for filing liens in
case of action under [the MS 102-72] Subdivision Agreement” in 1978. As
also required by ordinance, the Board adopted a resolution at the end of the
one-year period finding “the improvements have satisfactorily met the
guaranteed performance standards for one year after completion and
acceptance.”
      The developer was required to obtain or dedicate drainage easements to
the County for certain drainage improvements. The parcel map for MS 102-
72 depicts two drainage easements and a note indicating they are “dedicated
to Contra Costa County for drainage purposes.” The actual drainage
easement dedication language is contained in a separate document entitled
“Offer of Dedication” that was recorded in 1975. It provided that the
developer “being the present title owner(s) of record of the herein described

                                        5
parcel of land, do hereby make an irrevocable offer of dedication to Contra
Costa County and its successor or assign, of an easement for storm, flood and
surface water drainage, including construction, access, or maintenance of
works, improvements and structures, . . . or the clearing of obstructions and
vegetation, upon the real property . . . described as follows . . . .” The
document refers to the parcel map for the location of the easements. It
further states, “It is understood and agreed that CONTRA COSTA COUNTY
and its successor or assign shall incur no liability with respect to such offer or
dedication, and shall not assume any responsibility for the offered parcel of
land or any improvements thereon or therein, until such offer has been
accepted by appropriate action of the Board of Supervisors, or of the local
governing body of its successor or assign.” In December 1975, the County
issued and recorded an order stating that the offer was “ACCEPTED for
recording only.” (Italics added.)1
      The subdivision process for Subdivision 4983 took place a few years
after MS 102-72 was completed. The County required the developer of this
subdivision to make drainage improvements as well. The improvements
appear to have been more modest and included an asbestos cement pipe
coupled to a corrugated steel pipe storm drain to collect storm water runoff
from Via Ferrari, a small private street within the subdivision, and carry it to
an outlet at the Creek. The County did not design, construct or install the
drainage improvements on Subdivision 4983. It did inspect the drainage
plans and the improvements as required by local ordinance.

      1 Six months later, it rescinded that order because of an error in the
subdivision number and issued and recorded a corrected order, again
providing that the acceptance of the offer was “for recording only.”

                                         6
      On the subdivision map, the developer offered to dedicate two drainage
easements to the County. The County expressly did not accept or reject the
offer to dedicate the easements.
      There is no record of the County ever expressly accepting the offers of
the subdivision developers for either MS 102-72 or Subdivision 4983 to
dedicate drainage easements. There is no record of the County indicating it
has ever performed maintenance or repair of the drainage improvements
constructed on MS 102-72 or Subdivision 4983. Nor are there any County
records indicating the County performed maintenance of or repairs to
Murderer’s Creek at or upstream of the subdivisions.
      Owners purchased properties in the subdivisions three to four decades
after the subdivision maps were approved. In 2011, Brian Shenson and
Emily Shenson purchased real property at 1904 Via Ferrari in
Subdivision 4983 (the Shenson Property). The Creek flows along the
Shenson Property’s northeasterly property line. In 2016, Megan Frantz and
David Mariampolski purchased property near the Shenson Property at
18 Kelly Ann Court in MS 102-72 (the Frantz Property). The Creek flows
along or near the Frantz Property’s southwesterly property line.2
      In early 2016, the spillway the developer had constructed four decades
earlier failed and collapsed into the Creek bed. The uncontrolled discharge of
water into the Creek caused a scour hole to form and expand, eventually onto
the neighboring private subdivisions. Owners allege the scour hole caused

      2 Owners contend that a portion of MS 102-72 that includes part of the
Creek where it adjoins the lot that later became the Frantz Property was
deeded to the Pleasant Hill Park District and became part of Brookwood
Park. The Park District is not a party to this appeal. Whether some of the
improvements are on the Frantz Property or the Park District’s property is
not material to this appeal.
                                       7
erosion and subsidence damage to their respective properties. Owners
contend the Government Entities are responsible for the formation of the
scour hole because they failed to maintain the Creek’s bed and banks and
refused to repair or replace the spillway after it failed. In 2017–2018, the
expanding scour hole contributed to the failure of a second spillway that was
located 20 feet north of the first spillway and had served the water discharge
needs of Subdivision 4983.
                                        II.
             Complaint and Motion for Summary Judgment
      The operative third amended complaint alleged causes of action for
inverse condemnation, trespass, nuisance and dangerous condition of public
property.3 Owners alleged the County was responsible for the damage the
Creek and drainage improvements caused to their properties for several
reasons. First, the County approved subdivision MS 102-72; second, it
required the developer of that subdivision to construct the drainage
improvements, including a pipeline, a spillway and a catch basin; third, it
used those facilities to discharge water from another subdivision and from
city streets into the Creek; fourth, it required the developer to offer to
dedicate to the County an easement over the property containing those
improvements and portions of the bed and banks of the Creek; and fifth, it
permitted and encouraged private development of properties upslope from
Owners’ properties. Owners further alleged that the County accepted the
drainage improvements from the developer, used them for public purposes,
approved subdivision maps depicting the drainage easements and now “owns

      3  The pleading also included claims against the Pleasant Hill Park
District. The claims against the Park District are not the subject of this
appeal.
                                        8
and controls” the land within the drainage easements. They alleged that the
County “approved, owned, operated, controlled, repaired and/or maintained a
public drainage system” of which the Creek is a part and that the drainage
system caused damage to Owners’ properties.
      Owners alleged that the Contra Costa County Flood Control and Water
Conservation District (District) incorporated the Creek into the public
drainage system through its establishment of a statutory drainage area
known as Drainage Area 46 that includes the Creek, Owners’ properties and
other properties in the area. They alleged the County and District assessed
and continue to assess “storm drainage fees” from property owners within
Drainage Area 46 to offset the increased burden that new and expanding
development in the area has put on the public drainage system. They further
alleged that the District chose to hold the funds from the collected drainage
fees to be used for a future project instead of using them to install mitigation
measures against the increased water runoff or to repair the spillway.
      The County and the District filed motions for summary judgment or
summary adjudication. The County argued it was not liable to Owners for
inverse condemnation because (1) the Creek was not a public improvement
owned or controlled by the County; (2) its acts in approving the subdivisions
and requiring drainage improvements and offers of dedication did not
transform the Creek into a public storm drain system or otherwise make it or
the improvements a public work; (3) it had not accepted the offers of
dedication of drainage easements after they were made; and (4) it had not
made repairs or maintained the improvements or otherwise impliedly
accepted the offers. Finally, the County argued that Owners’ related tort
causes of action for nuisance, dangerous condition of public property, and

                                       9
trespass also fail since neither the Creek nor the drainage improvements
were public improvements owned or controlled by the County.
      The District made similar arguments. The District explained that it
was formed in 1951 and was statutorily authorized to establish “drainage
areas” and to “institute drainage plans for the specific benefit of such areas.”
It argued that none of its activities, including forming Drainage Area 46
“with the goal of implementing a regional concept-plan for flood protection to
protect areas in the City of Pleasant Hill downstream of Taylor Blvd.,”
adopting a Drainage Fee Ordinance, establishing a drainage facilities fund
for that project, and requesting (but not receiving) matching federal funds,
transformed the Creek into a District-owned or controlled public
improvement. Further, it argued that it was not an offeree and did not
accept the offers of dedication by the subdivision developers, did not provide
any storm drainage services, is not a landowner in the watershed, does not
divert flows from outside areas into the watershed, does not own any
upstream properties or discharge any runoff into the creek, and did not use or
otherwise impliedly accept the easements.
      In opposition to the County’s motion, Owners contended the County
was liable for inverse condemnation because it (1) required the developer of
MS 102-72 to install drainage improvements as a condition of approval so
that surface water from Gloria Terrace (a County road) and a neighboring
subdivision could be conveyed through MS 102-72 and into the Creek; (2)
required the developer to place drainage easements over these improvements
and dedicate them to the County; and (3) jointly with the District, exercised
dominion and control over the Creek by requiring all property owners within
Drainage Area 46 to discharge additional runoff caused by improvements to
their properties into the Creek.

                                       10
      Owners opposed the District’s motion on grounds similar to those in its
opposition to the County’s motion. Owners additionally argued that the
District incorporated the Creek into the public drainage system by (1)
creating Drainage Area 46; (2) compelling property owners who develop land
in the watershed to use the Creek to dispose of additional storm drainage;
and (3) collecting storm drainage fees from property owners for this use.
      As part of their oppositions, Owners submitted the declaration of
Douglas Flett, a civil engineer. As relevant to this appeal, the declaration
stated that if the County had intended the drainage improvements in
MS 102-72 to be private instead of public, it would not have required the
property owner to dedicate the drainage easements to the County for public
use. Further, if the County had intended for the owner to maintain the
improvements, the easements would have been conveyed to a homeowners’
association. The expert concluded that this was “evidence that at the time of
the creation of [MS 102-72], the parties understood that the County would
have the maintenance obligation for the drainage system that serves the
subdivision.” The County and the District objected to this testimony on the
bases of lack of foundation (Evid. Code, § 403), improper expert opinion (id.,
§ 801), and speculation (id., § 801, subd. (b)).
      The trial court granted summary judgment in favor of the County and
the District, concluding there was insufficient evidence to support the
assertion that they exerted control over or assumed responsibility for either
the Creek or the drainage system and that the County’s use of the Creek to
drain surface water from county roads and to require other riparian owners
in the watershed to do the same did not transform the Creek into a public
drainage system. The court held that under our Supreme Court’s decision in
Locklin v. City of Lafayette (1994) 7 Cal.4th 327 (Locklin), requiring the

                                        11
dedication of drainage easements as a condition precedent to subdivision
approval “does not demonstrate [defendants’] control over a natural
watercourse.” The undisputed evidence established that the County did not
accept the drainage easements on the Shenson Property and accepted the
easements on the Frantz Property for recording purposes only. The trial
court sustained the County’s objection to a portion of Flett’s declaration.
      Nor, the court held, were the District’s acts in collecting fees from
property owners evidence of control of the Creek or storm drain facilities.
The fees collected were “in service of a proposed plan that has not been
implemented.” There was no evidence that the District provided storm
drainage services or maintained any of the easements and the court
concluded the evidence failed to show control by the District.
      The court entered judgment in favor of the County and the District, and
Owners timely appealed.
                                DISCUSSION
                                       I.
                             Standard of Review
      Summary judgment is proper “if all the papers submitted show that
there is no triable issue as to any material fact and that the moving party is
entitled to a judgment as a matter of law.” (Code Civ. Proc., § 437c,
subd. (c).) A defendant seeking summary judgment “bears the burden of
persuasion that there is no triable issue of material fact and that [it] is
entitled to judgment as a matter of law.” (Aguilar v. Atlantic Richfield Co.
(2001) 25 Cal.4th 826, 850.) A defendant meets this burden by showing that
plaintiff “has not established, and cannot reasonably expect to establish” an
essential element of his claim. (Saelzler v. Advanced Group 400 (2001)
25 Cal.4th 763, 768.)

                                       12
      We review a grant of summary judgment de novo, which means we
“decide independently whether the facts not subject to triable dispute
warrant judgment for the moving party as a matter of law.” (Intel Corp. v.
Hamidi (2003) 30 Cal.4th 1342, 1348.) In deciding whether a material issue
of fact exists for trial, we “consider all of the evidence set forth in the papers,
except the evidence to which objections have been made and sustained by the
court, and all inferences reasonably deducible from the evidence.” (Code Civ.
Proc., § 437c, subd. (c).) We view the evidence in the light most favorable to
the plaintiffs, as the nonmoving parties, liberally construing their evidentiary
submission while strictly construing the defendants’ own showing and
resolving any evidentiary doubts or ambiguities in plaintiffs’ favor. (Saelzler
v. Advanced Group 400, supra, 25 Cal.4th at p. 768.)
                                        II.
                                Substantive Law
      A.    The Subdivision Map Act
      “The Subdivision Map Act is ‘the primary regulatory control’ governing
the subdivision of real property in California. [Citation.] The Act vests the
‘[r]egulation and control of the design and improvement of subdivisions’ in
the legislative bodies of local agencies, which must promulgate ordinances on
the subject. ([Gov. Code,] § 66411.) The Act generally requires all
subdividers of property to design their subdivisions in conformity with
applicable general and specific plans and to comply with all of the conditions
of applicable local ordinances.” (Gardner v. County of Sonoma (2003)
29 Cal.4th 990, 996-997 (Gardner), fn. omitted.)
      “Ordinarily, subdivision under the Act may be lawfully accomplished
only by obtaining local approval and recordation of a tentative and final map
pursuant to [Government Code] section 66426, when five or more parcels are

                                        13
involved, or a parcel map pursuant to [Government Code] section 66428 when
four or fewer parcels are involved. [Citation.] A local agency will approve a
tentative and final map or a parcel map only after extensive review of the
proposed subdivision and consideration of such matters as the property’s
suitability for development, the adequacy of roads, sewer, drainage, and other
services, the preservation of agricultural lands and sensitive natural
resources, and dedication issues. (See, e.g., [Gov. Code,] §§ 66451–66451.7,
66452–66452.13, 66453–66472.1, 66473–66474.10, 66475–66478.)” (Gardner,
supra, 29 Cal.4th at p. 997.)
      “By generally requiring local review and approval of all proposed
subdivisions, the Act aims to ‘control the design of subdivisions for the benefit
of adjacent landowners, prospective purchasers and the public in general.’
[Citation.] More specifically, the Act seeks ‘to encourage and facilitate
orderly community development, coordinate planning with the community
pattern established by local authorities, and assure proper improvements are
made, so that the area does not become an undue burden on the taxpayer.’ ”
(Gardner, supra, 29 Cal.4th at pp. 997-998.)
      The Act defines “[d]esign” to include, among other things, “drainage
and sanitary facilities and utilities, including alignments and grades thereof.”
(Gov. Code, § 66418.4) It defines “[i]mprovement” to include “any street work
and utilities to be installed, or agreed to be installed, by the subdivider on the
land . . . as are necessary for the general use of the lot owners in the
subdivision and local neighborhood traffic and drainage needs as a condition
precedent to the approval and acceptance of the final map thereof.” (§ 66419,
subd. (a).) It has been said that “[o]ne of the main purposes of the

      4All further statutory references are to the Government Code unless
otherwise specified.
                                       14
Subdivision Map Act is to require the subdivider to install properly the
streets and drains under the provisions of that act.” (City of Buena Park v.
Boyar (1960) 186 Cal.App.2d 61, 67.)
      The Act provides “the key authorization for imposing conditions on
development.” (4 Manaster & Selmi, Cal. Environmental Law and Land Use
(2022) Subdivision Regulation (4 Manaster & Selmi) § 61.03[6] at pp. 61-28 to
61-28.1 (rels. 51-10/2009, 60-3/2014).) “In approving subdivisions, local
agencies require that land be dedicated for public uses, that public and
private improvements be built, that design review fees be paid to cover the
cost of design review, and that capital or impact fees be paid to cover the
subdivided land’s share of the costs for a wide range of amenities.” (Id.,
§ 61.06[1] at p. 61-74.2 (rel. 76-4/2022).)
      The Act contains “provisions authorizing local agencies to impose
specific conditions on subdivision approvals to achieve certain public
purposes or offset particular impacts.” (4 Manaster & Selmi, supra,
§ 61.06[2] at pp. 61-74.2 to 61-74.3 (rel. 76-4/2022); see Youngblood v. Board
of Supervisors (1978) 22 Cal.3d 644, 652 [“The Subdivision Map Act
contemplates that the local agency, when it approves a tentative map, will
normally attach conditions to that approval, such as the completion of
planned subdivision improvements, and will approve the final map only after
certifying that the subdivider has complied with those specified conditions”].)
This includes improvements for such things as streets, utilities and drainage.
(4 Manaster & Selmi, supra, § 61.03[6] at pp. 61-28 to 61-28.1 (rels. 51-
10/2009, 60-3/2014).) Indeed, requiring the subdivider to install drainage has
been described as one of “several salutary purposes” of the Act. (Pratt v.
Adams (1964) 229 Cal.App.2d 602, 605-606.) It is typical for a subdivision
agreement to require a subdivider to perform the work constructing

                                        15
improvements in accordance with plans and specifications previously
approved by the local agency and to require security to ensure performance of
the work. (4 Manaster & Selmi, supra, § 61.04[9][b][ii] at pp. 61-58 to 61-59
(rel. 38-3/03).) Another common condition is that the subdivider dedicate or
make an irrevocable offer of dedication for such purposes such as streets,
drainage, public utilities or public access. (See § 66475.)
      B.    Inverse Condemnation

      The primary theory asserted by Owners is based on the law of inverse
condemnation. To understand the parties’ allegations and arguments and
the issues in the summary judgment proceedings at the heart of this appeal,
some background about tort and inverse condemnation law as it pertains to
subdivisions and drainage is required.
      A public entity may be liable as a property owner when alterations or
improvements to its own upstream property result in the discharge of an
increased volume of or velocity of surface water in a natural watercourse
causing damage to the property of a downstream owner. (Locklin, supra,
7 Cal.4th at p. 337.) As with any upstream property owner, whether public
or private, a government entity is only liable if, considering all of the
circumstances, its conduct was unreasonable and the lower property owner
acted reasonably. (Ibid.) Damage resulting from improvements on publicly
owned property may also result in inverse condemnation liability. (Id. at
pp. 337-338.)
      Further, a government entity may be liable in inverse condemnation
where the increased volume or velocity of surface waters and resulting
damage are caused by discharge of increased surface waters from public
works or improvements on publicly owned land or if it has incorporated the
watercourse or public improvements into a public drainage system. (Locklin,

                                        16
supra, 7 Cal.4th at pp. 337-338.) The theory underlying inverse
condemnation liability in these contexts is similar to that for inverse
condemnation generally: the downstream owner “may not be compelled to
accept a disproportionate share of the burden of improvements undertaken
for the benefit of the public at large.” (Id. at p. 338; see also id. at p. 367;
Belair v. Riverside County Flood Control Dist. (1988) 47 Cal.3d 550, 558
[decisive consideration is whether owner of damaged property if
uncompensated would contribute more than his proper share to public
undertaking].) Similar to a tort, under inverse condemnation, the
reasonableness of the public entity’s conduct matters. The public entity will
be liable only “if it fails to use reasonably available, less injurious
alternatives.” (Locklin, supra, at p. 338.) In addition, the downstream owner
must take reasonable measures to protect his property and if he fails to do so,
there is no liability. (Ibid.)
       “A storm drainage system constructed and maintained by a public
entity” is a public work. (Souza v. Silver Development Co. (1985)
164 Cal.App.3d 165, 170.) To convert an existing watercourse into a public
work, “[a] governmental entity must exert control over and assume
responsibility for maintenance of the watercourse if it is to be liable for
damage caused by the streamflow on a theory that the watercourse has
become a public work.” (Locklin, supra, 7 Cal.4th at p. 370.) The same is
true of converting privately constructed improvements into public works.
(Ullery v. County of Contra Costa (1988) 202 Cal.App.3d 562, 570 (Ullery).)
“Official acts of dominion and control constituting acceptance of the private
drainage system can be shown if the public entity does maintenance and
repair work. [Citations.] Use of land for a public purpose over time may
constitute implied acceptance of the offer of dedication. [Citation.] On the

                                         17
other hand, where ‘there is no acceptance of a street or the drainage system
within it, there is no public improvement, public work or public use and
therefore there can be no public liability for inverse condemnation.’ ” (Id. at
pp. 568-569.)
      “[I]nverse condemnation liability will not lie for damage to private
property allegedly caused by private development approved or authorized by
the public entity, ‘where the [public entity’s] sole affirmative action was the
issuance of permits and approval of the subdivision map.’ ” (Ullery, supra,
202 Cal.App.3d at p. 570.)
                                       III.
                       Plaintiffs’ Theories on Appeal
      Owners assert three theories to support their claims of inverse
condemnation, one as to the County only and two as to the County and the
District jointly.
      As to the County alone, Owners claim the MS 102-72 spillway was a
component of a drainage system that must be considered public. This is so,
they argue, because (1) the County required the subdivider to construct it as
a condition of approval of the subdivision; (2) it serves two off-subdivision
needs and provides no benefit to the subdivision itself; and (3) the drainage
system does not follow any “natural” drainage path but instead collects and
conveys water that would never enter the subdivision if not for the system.
This evidence, they contend, raises a triable issue whether the drainage
system is a public use under inverse condemnation standards.
      As to the County and the District jointly, Owners claim there is a
triable issue whether defendants “have incorporated Murderer’s Creek into
the public drainage system through their joint management, and evident
mismanagement, of Drainage Area 46.” Owners also claim that even if

                                       18
defendants’ “joint management of and control over the Murderer’s Creek
watershed did not incorporate the Creek into the public drainage system,”
they are liable “if their management of Drainage Area 46 places a
disproportionate and therefore ‘unreasonable’ burden on downstream
riparian property owners.” They contend the trial court erred by failing to
apply the six “Locklin factors” required to analyze this issue.
                                        IV.
                 Plaintiffs’ Claims Fail As a Matter of Law.
        Whether an improvement or waterway is a public use or public work
for purposes of inverse condemnation liability is a question of law when
factual issues are not in dispute. (See Locklin, supra, 7 Cal.4th at pp. 369-
370.)
        A. Plaintiffs Have Not Raised a Triable Issue Whether the
           Spillway Is a Public Improvement or Use and Given the
           Undisputed Facts It Is Not a Public Work As a Matter of Law.
        Locklin established that “a governmental entity may be liable under
the principles of inverse condemnation for downstream damage caused by an
increased volume or velocity of surface waters discharged into a natural
watercourse from public works or improvements on publicly owned land” “if it
fails to use reasonably available, less injurious alternatives, or if it has
incorporated the watercourse into a public drainage system or otherwise
converted the watercourse itself into a public work.” (Locklin, supra,
7 Cal.4th at pp. 337-338, italics added.) Owners contend there is a triable
issue of fact as to whether the MS 102-72 spillway—the failure of which they
assert caused turbulence that damaged their land—was a public
improvement.
        The three facts Owners contend support a finding of public
improvement or use are, as we have said, that the County required the

                                        19
developer to construct a drainage system and place it within an easement
dedicated to the County; that the spillway served the needs of two areas
outside of MS 102-72 while “providing essentially no benefit to the residents
of [MS 102-72]”; and that the drainage system collects water from outside its
“natural” drainage path and directs it to the discharge point at the Creek.
         1. Requiring Construction of the Drainage System and an
            Offer of Dedication Did Not Convert Private Improvements
            into Public Works.
      There is no genuine dispute about the material facts concerning the
spillway or the other drainage improvements. The County imposed on the
developer a condition requiring it to “construct, install and complete . . . tract
drainage,” and a County ordinance required it to collect and convey “[a]ll
surface waters flowing from the subdivision in any form or manner” from the
development to the nearest natural watercourse with a definable bed and
banks or to a public storm drainage facility. It required the developer to offer
to dedicate easements for drainage purposes to the County.
      The developer of MS 102-72—not the County—designed and built
improvements to satisfy these requirements, including underground drainage
pipelines, catch basins, and an outfall at the Creek with a “spillway feature
(‘Spillway’) comprised of grouted and loose rock riprap lining the earthen
banks of the Creek.” The waters flowing through the pipelines consisted of
runoff from MS 102-72, including a private road serving that subdivision
known as “Kelly Ann Court”; runoff from an adjacent subdivision referred to
as “Sub. 4234”; and runoff from Gloria Terrace, a county road adjacent to the
subdivision. The purpose of the spillway was to protect the bed and bank of
Murderer’s Creek against erosion from the waters spilling into the creek from
the pipeline.

                                        20
      The County required the subdivider to offer easements to the County
for drainage purposes, and the subdivider did so. The County has thus far
never expressly accepted the offer. There are no records of the County ever
having maintained or repaired the pipeline, outlet or spillway. The County
has never performed maintenance or repairs to the portion of Murderer’s
Creek upstream of plaintiffs’ properties or installed any improvements in the
creek bed or channel.
      The facts Owners claim indicate the spillway is a public work are
essentially undisputed.5 And for the following reasons, we conclude as a
matter of law that they do not show the County converted the Spillway into a
public drainage system.
      Owners’ argument is somewhat difficult to follow. It begins with the
proposition that “ ‘construction and maintenance of storm drainage systems
are matters of “public policy,” and such a system created by a public entity
becomes a “public improvement” and a “public use.” ’ ” Citing pre-Locklin

      5  Owners assert, without citation, that the drainage improvements
required as conditions for their subdivision “provid[e] essentially no benefit to
the residents of the Subdivision.” (Italics added.) There is no evidence to
support this assertion, and the County’s evidence shows the opposite is true.
For example, a catch basin and the pipeline buried under the MS 102-72
collected and carried runoff from that subdivision, including the private cul
de sac that serves it, to the outfall and into the creek. The spillway beneath
the outfall was designed to prevent erosion of the creek bed and banks
adjacent to it, which were part of the subdivision.
      Owners also assert, again without citation, that the drainage “system”
that the County required the subdividers to construct convey waters that
would “never enter the Subdivision . . . were it not for the drainage system.”
We have reviewed the evidence proffered by Owners and find no support for
this assertion. Further, we note it is undisputed that the road and
subdivision that Owners describe as the “off-subdivision” areas served by
these improvements, Gloria Terrace and Subdivision 4234, are immediately
adjacent to MS 102-72.
                                       21
cases for that proposition, it proceeds to contend that “[i]t does not matter
whether the public entity constructed the drainage improvements itself or
whether, as is more common (and happened here), the public entity required
a private property owner to construct [them] through its ‘approval of the
subdivision maps and plans which include the drainage systems.’ ” The 1963
decision it quotes for that proposition, Frustuck v. City of Fairfax,
212 Cal.App.2d 345 (Frustuck), has since been rejected by this court in
Ullery, rejecting the proposition in Frustuck for which plaintiffs cite it here.
Division Three of this court stated, “Appellants misconstrue the law when
they state that the subdivision map approval process represents a sufficient
level of governmental involvement to constitute a public use or improvement
subjecting the public entity to inverse condemnation liability. The cases do
not stand for the proposition that approval alone creates liability in inverse
condemnation.” (Ullery, supra, 202 Cal.App.3d at p. 571.)
      Further, Frustuck was implicitly overruled by Locklin. In Locklin, the
plaintiffs alleged that the city and county had allowed development of
properties upstream of plaintiffs’ properties, required developers to construct
roads, rights of way, culverts, storm drains and other public improvements in
the watershed and required irrevocable offers of dedication of storm drainage
easements on creekside properties as a condition of development permits.
(Locklin, supra, 7 Cal.4th at pp. 340-342 & fn. 10.) Locklin held neither this,
nor evidence that the city assisted residents in removing falling trees from
the creek bed with permission from the owners and repaired an outfall above
the creek, was sufficient to establish that the creek had been converted into a
public work or improvement or a part of the public storm drainage system. A
government entity, it opined, “must exert control over and assume
responsibility for maintenance of the watercourse if it is to be liable for

                                        22
damage caused by the streamflow on a theory that the watercourse has
become a public work.” (Id. at p. 370, italics added.) Without a showing that
the city or other defendants exercised control over the creek, it “remain[ed] a
privately owned natural watercourse.” (Id. at pp. 370-371.)
      The Locklin court was not moved by the assertion that the city had
required drainage easements. Noting that the evidence did not establish an
express or implied acceptance of the drainage easements, the court expressed
doubt that “requiring and/or accepting drainage easements across private
property to a privately owned natural watercourse” is even “evidence of
control over the watercourse itself.” (Locklin, supra, 7 Cal.4th at p. 370,
fn. 21, italics added.)
      Notably, Owners cite no current authority for the proposition that a
county’s imposition of conditions of approval through the Subdivision Map
Act, including requirements that drainage improvements be implemented
and that an offer to dedicate easements be made converts the improvements
or the watercourse they affect into a public work, and we are aware of none.
And Locklin repudiated the notion when, in rejecting an argument that the
evidence in that case converted a creek into a public work, it opined,
“Utilizing an existing natural watercourse for drainage of surface water
runoff and requiring other riparian owners to continue to do so does not
transform the watercourse into a public storm drainage system.” (Locklin,
supra, 7 Cal.4th at p. 370.) The latter is precisely what the County did in
this case when it adopted an ordinance requiring upstream property owners
of the Creek in the watershed to convey surface waters to and discharge them
into the Creek. In doing so, it exercised its authority under the Subdivision
Map Act to regulate the “design and improvement” of subdivisions by
requiring subdivision developers to construct drainage improvements. (See

                                       23
§§ 66411, 66418, 66419, 66421; 7 Miller & Starr, Cal. Real Estate (4th ed.
2022) §§ 20:1, 20:25.)
      Requiring drainage-related improvements as conditions of approval of a
map and offers to dedicate of easements is not an exercise of control over, or
an assumption of responsibility for, maintenance of the improvement or the
watercourse—especially where, as here (and in Locklin), there has been no
acceptance of the dedication. (See Locklin, supra, 7 Cal.4th at p. 370 & fn. 21
[questioning whether even accepted offer of dedication would suffice].) The
County also argues persuasively that Ruiz v. County of San Diego (2020)
47 Cal.App.5th 504 (Ruiz) and the cases it relies on (Locklin, supra, 7 Cal.4th
327, DiMartino v. City of Orinda (2000) 80 Cal.App.4th 329 (DiMartino) and
Ullery, supra, 202 Cal.App.3d 562), likewise refute the notion that
improvements constructed in connection with a subdivision over which
easements are offered but not accepted by the public entity, nonetheless
become public works when they are used for drainage of public or other
private properties. (See Ruiz, at pp. 509, 515-519; Ullery, at p. 570 [although
creek was part of system draining 40-acre watershed, absence of dominion
and control by public entities supported finding of no public use].) This is so
even where the public has used the improvements for drainage for decades
(see Ruiz, at pp. 514, 516 [50 or “ ‘over 60’ ” years].)
      Owners attempt to distinguish Locklin, claiming in that case the city
had required developers “to place drainage easements over natural drainage
swales across private property,” whereas here the County sought “to allow
future County access to the drainage improvements (curbs, gutters, two drop
inlets and catch basins, two underground drainage pipelines, and the
MS 102-72 Spillway that ultimately failed) that the County had required [the
developer] to install to serve two off-subdivision drainage needs. These

                                         24
drainage improvements collect and convey surface water from two off-
Subdivision locations onto and across the Subdivision, into an area that this
water could never reach without them.”
      While Owners’ argument is not entirely clear, we take it to mean that
by requiring offers to dedicate easements with respect to drainage
improvements that served an adjacent subdivision and an adjacent street
owned by the County (Gloria Terrace) and by diverting surface water to catch
basins and pipelines to convey it to the Creek, the County in effect converted
the improvements into public works. They cite no authority for this
proposition, and we do not agree with it.
      Locklin held that using an existing natural watercourse for drainage of
surface water runoff and requiring other riparian owners to do so “does not
transform the watercourse into a public storm drainage system.” (Locklin,
supra, 7 Cal.4th at p. 370.) We hold that requiring and using drainage
improvements within a subdivision to convey water, including from an
adjacent public road and adjacent subdivision, does not convert the
improvements into public works either. As the County puts it, “Drainage
improvements in all developments are designed to accommodate the
anticipated storm water runoff quantities to be received by the
development—including any runoff flows emanating from beyond a
subdivision’s boundary.” Further, because developments “disrupt the natural
drainage patterns,” “installation of artificial drainage facilities that collect
and convey the runoff” that before “may have been conveyed as natural sheet
flows” is necessary “to ensure the waters will safely pass through the
community without causing damage.”

                                        25
         2. That the Drainage Improvements Serve Some Off-
            Subdivision Needs Does Not Convert Them into Public
            Works.
      Contrary to Owners’ arguments, requiring artificial drainage facilities
and conveying water across properties over which it might not have flowed
when the area was undeveloped does not convert those improvements into
public works. Development requires that drainage systems be constructed to
channel water beneath or around the obstacles development creates. A
government could not require owners whose properties are not adjacent to a
natural watercourse (i.e., landlocked) to drain waters from their properties
into such a watercourse without allowing them to flow through properties
that are closer to and/or adjacent to the watercourse. Thus, waters from
landlocked properties must at least sometimes be conveyed through drainage
improvements on other properties to reach a natural watercourse. This is
recognized by the County in its ordinance regarding conveyance of surface
waters, which provides that when “surface waters must be collected or
conveyed beyond the boundaries of the subdivision in order to discharge into
a natural watercourse,” appropriate easements must be obtained from “all
property owners between the boundaries of the subdivision and the point at
which the surface waters will be discharged into a natural watercourse.”
      For these reasons, it is not surprising that the Subdivision Map Act
contemplated that improvements would be used for the good of the
subdivision and properties beyond it. Its aim was to require local
governments to exercise control over “ ‘the design of subdivisions for the
benefit of adjacent landowners’ ” as well as “ ‘prospective purchasers and the
public in general’ ” (Gardner, supra, 29 Cal.4th at p. 997.) It defined
“[i]mprovement” to include work “necessary for the general use of the lot
owners in the subdivision and local neighborhood . . . needs.” (§ 66419,

                                      26
subd. (a), italics added.) As a leading commentator has put it, “[t]he local
authorities have a great deal of latitude to require a subdivider to make
adequate arrangements for drainage and sewage disposal both within and
outside of the subdivision.” (7 Miller & Starr, Cal. Real Estate, supra,
§ 20:30.)
      A rule that government-required improvements on one subdivision are
public if they serve drainage needs of properties outside that subdivision or
convey water that might not naturally have flowed through the servient
subdivision would undermine the purposes of the Subdivision Map Act.
Indeed, local governments would be reluctant to “ ‘facilitate orderly
community development, coordinate planning with the community
pattern . . . , and assure proper improvements are made’ ” (Gardner, supra,
29 Cal.4th at pp. 997-998) if doing so would impose responsibility and the
associated costs on them for maintaining and repairing all such
improvements.
      Owners contend our decision in DiMartino, supra, 80 Cal.App.4th 329
supports the rule they propose because it “distinguished the installation of
drainage improvements by private property owners to achieve private
objectives from County-mandated drainage improvements required by public
entities to achieve public objectives.” Owners misconstrue what we decided
in DiMartino. In concluding the drainage pipe installed under the plaintiffs’
house was not a public work, this court focused on whether the city had
played any role in constructing that pipe and concluded the evidence did not
show that it had. (Id. at pp. 336-344.) We referred to the purpose for which
the pipe was built simply as evidence that it had been installed by an earlier
owner of the lot. We did not hold or suggest that improvements that serve

                                       27
drainage needs that extend beyond the subdivision are necessarily public
works. (Id. at p. 344.)
      On the contrary, as the County points out, in DiMartino we rejected the
argument that “connection of a private pipe segment to an admittedly public
pipe segment converts the former to a public improvement.” (DiMartino,
supra, 80 Cal.App.4th at p. 343; see also Ruiz, supra, 47 Cal.App.5th at
p. 518 [fact that pipe was part of system that was used to drain valley
watercourse, even over an extended period, did not constitute implied
acceptance of drainage easement].) We further observed that “such a rule
would allow circumvention of the Subdivision Map Act: a developer would no
longer need to comply with requirements of dedication and acceptance,
connection of any pipe on private property to a public roadway cross-culvert
would transform the private pipe to a public one. We have found no case
recognizing such a doctrine.” (DiMartino, at p. 343.)
      Owners also contend there is a triable issue here because the County
“both refused to either ‘accept or reject’ the drainage easements [it] required
developers to place over the bed and banks of the Creek” and therefore may
have effectively accepted them and converted the improvements and the
Creek into public works. Owners disregard the well-established rule that an
acceptance of an offer to dedicate must be unqualified and unequivocal. (See
Mikels v. Rager (1991) 232 Cal.App.3d 334, 353-354 [valid acceptance of offer
must be “absolute and unqualified”]; Flavio v. McKenzie (1963)
218 Cal.App.2d 549, 551-552 [“ ‘To effect a dedication of land by a private
owner to public use, it is essential that there be an unequivocal offer of
dedication by the owner and an unequivocal acceptance of the offer by the
public’ ”].) “ ‘A dedication without acceptance is, in law, merely an offer to
dedicate, and such an offer does not impose any burdens nor confer any

                                       28
rights, unless there is an acceptance.’ ” (Mikkelsen v. Hansen (2019)
31 Cal.App.5th 170, 176.)
      With respect to the drainage improvements on MS 102-72, the County
did not accept the offer for the purpose it was offered, i.e., to access the
improvements. It accepted the offer only for the purpose of recording the
deed. An acceptance “for recording only” is not the kind of unequivocal and
unconditional acceptance required to create a valid dedication. As for
Subdivision 4983, the County stated it “did not accept or reject on behalf of
the public any of the streets, roads, avenues or easements shown [on the
Final Map] as dedicated to public use.” This was not an unequivocal or
absolute acceptance. Given that the offer was irrevocable, declining to accept
or reject it left open to the County the option to accept it at some later time.
It is undisputed that it never expressly did so.
      Although there can be implied acceptance of an offer of dedication, it is
undisputed that the County made no effort to maintain or repair the
Spillway, any other improvements or the Creek itself. “Absent an easement
or accepted dedication, liability is imposed on a public entity only when the
public entity has exercised dominion and control over the private property.”
(Ruiz, supra, 47 Cal.App.5th at p. 523.) In other words, in the absence of an
express acceptance, there must be evidence of implied acceptance of
dedication through, for example, the public entity’s assumption of
maintenance or repair of the property. (Ibid.) In Ruiz, the court held the fact
that public water drained through a privately owned pipeline did not
constitute an implied acceptance of an offer of dedication that the public
entity had previously expressly rejected. (Id. at p. 517.) The court indicated
a previous case answered the question of “how much more” was required to
constitute an implied acceptance, noting that in the earlier case “the public

                                        29
entity was substantially involved in installing the privately owned pipe. For
example, a surveyor employed by the public entity instructed the property
owner ‘ “exactly what pipe to lay and how to do it” ’ and “provided the trucks,
dirt, and water to complete the installation.” (Id. at p. 518.) There is no
similar evidence here, and the County has provided evidence showing that it
never owned, constructed or repaired the drainage improvements.6
          3. There Was No Implied Acceptance of the Drainage
             Easements by the County.
      Owners further contend they have raised a triable issue of fact as to
whether the County otherwise assumed control or maintenance of the
spillway because (1) it required the developer to install the drainage
improvements; (2) its acceptance of the easements for MS 102-72—for
recording only—suggests it impliedly accepted the easement; (3) there is a
letter from the developer’s engineer to the County purportedly confirming the
County’s obligation to maintain the drainage system; and (4) the October 22,
1975 subdivision agreement confirmed that the County would assume
responsibility for the drainage improvements after one year.
      We begin with the first two points. As we have explained, under
Locklin and other cases, requiring improvements and easements does not
convert the improvements into public works. It is likewise insufficient to
constitute implied acceptance. To hold otherwise would be an end run

      6 Owners also argue that in requiring the dedication of the drainage
easements, the County’s “purpose” was “to ensure [it] would have access to
the system in perpetuity to perform periodic maintenance,” citing the
declaration of Flett, their civil engineering expert. Even if the Flett
declaration had been competent evidence of the County’s purpose or intent
(which we discuss further below), it would not matter. “ ‘[A] dedication, like a
contract, consists of an offer and acceptance, . . . proof of which must be
unequivocal.’ ” (Biagini v. Beckham (2008) 163 Cal.App.4th 1000, 1009.) A
party’s unstated purpose or intent is not acceptance of an offer.
                                       30
around those cases. As we have discussed, Ullery and Ruiz indicate the kinds
of conduct necessary for implied acceptance, such as substantial involvement
in construction of the improvement or performing “maintenance and repair
work.” (Ullery, supra, 202 Cal.App.3d at p. 568; accord, Ruiz, supra,
47 Cal.App.5th at p. 523 [“Absent an easement or accepted dedication,
liability is imposed on a public entity only when the public entity has
exercised dominion and control over the private property”].) The undisputed
evidence shows the County did not construct the improvements and
performed no maintenance or repair work on the improvements.
      Turning to the third item, the letter from the developer’s engineer, that
letter is not competent evidence that the County agreed to maintain the
spillway. In the letter, the engineer provided the County with a cost estimate
of the improvements for MS 102-72 and stated, “The following also includes
the drainage system which will lie within dedicated easements in said
subdivision and which shall be maintained by the county upon acceptance.”
(Italics added.) The County objected to the letter as lacking foundation and
improper opinion. The trial court did not rule on the objection but concluded
the letter was not evidence of an agreement by the County that the drainage
improvements would become public and be maintained by the County. We
agree. The engineer is not a party to the subdivision agreement with the
County, and his letter does not refer to that or any other agreement between
the developer and the County. The engineer’s assertion may simply reflect an
assumption or prediction that the easements would be accepted by the
County. It is not evidence that the County agreed to accept the offer of
dedication.
      Finally, Owners argue that the County’s agreement to maintain the
drainage improvements was “reaffirmed, albeit ambiguously, by the

                                      31
October 22, 1975, subdivision agreement” between the County and the
developer for MS 102-72. The agreement includes a provision that following
the completion of work (including the drainage improvements) for MS 102-72,
the developer agreed to maintain the work and repair any defects for a one-
year period. Owners argue the implication was that the County would
assume maintenance of the drainage system after the one-year period. The
inference Owners suggest we draw is not a reasonable one. The provision for
a one-year period guaranteeing the adequacy of the improvements, which is
required by county ordinance, is essentially a warranty that the
improvements will work and, that if they fail during the warranty period, the
developer will repair any defect. The Subdivision Map Act contemplated local
governments would take steps to ensure that subdividers performed the
obligations they undertook, including to construct required improvements.
(See §§ 66499 et seq.; 74 Ops. Cal. Atty. Gen. 89 (1991).) The duration of a
warranty or guarantee has no tendency to show the local government agreed
to accept long-term responsibility for the improvements the subdivider
warranted.
      B. Plaintiffs Have Not Established a Triable Issue As to
         Whether the Creek Was Incorporated into the Public
         Drainage System.
      Owners separately contend a triable issue of fact exists as to whether
the Creek has been incorporated into the public drainage system through the
Government Entities’ management of Drainage Area 46. Specifically,
Owners argue that through their management, defendants are (1) requiring
property owners developing parcels within the watershed to drain increased
surface water runoff into the Creek; (2) collecting drainage fees from property
owners for this use; and (3) choosing not to require property owners to install
mitigation measures to reduce downstream runoff.

                                      32
      Owners’ first point lacks merit, as “[u]tilizing an existing watercourse
for drainage of surface water runoff and requiring other riparian owners to
continue to do so does not transform the watercourse into a public storm
drainage system.” (Locklin, supra, 7 Cal.4th at p. 370.) There must be some
affirmative action by the public entity to assume ownership or responsibility
of the watercourse. (Ibid.) Here, neither the County nor the District had any
ownership interest in the Creek nor performed any maintenance on the
Creek on or upstream of Owners’ properties. Owners’ reliance on Souza v.
Silver Development Co., supra, 164 Cal.App.3d 165 is unavailing. There, this
court found there was sufficient evidence to support the trial court’s finding
that a creek had been incorporated into the public drainage system because
the city “required the developer to construct storm drains to carry surface
water into the creek and accepted the dedication of those drains.” (Id. at
p. 170, italics added.) The city also required and accepted an easement for
drainage along the creek channel. (Ibid.) Such express acceptance is wholly
absent here.
      Second, the evidence shows that the Government Entities do not
provide any storm drainage services to Owners’ properties or any upstream
properties within the watershed. The “drainage fees” Owners reference are
fees that the District collected pursuant to the Drainage Fee Ordinance
enacted in 1988. The fees are imposed on all new development in Drainage
Area 46 based on a dollar amount of square foot of impervious surface area
developed. Revenue generated from these fees was placed in a fund intended
to cover a local match that was required to implement a flood protection
project. The project was not implemented because it did not meet federal
requirements, and the District is now working with the City of Pleasant Hill

                                      33
to determine whether to create a new drainage plan that would include new,
proposed drainage improvements.
      The District’s act in implementing and collecting drainage fees to fund
a proposed project that was never built does not raise a triable issue as to
whether the District or the County incorporated the Creek into a public
drainage system. Finally, that the Government Entities allegedly could have
but did not require upstream property owners to install mitigation measures
to offset the downstream runoff is not an affirmative act that demonstrates
public control or dominion over the Creek. (Locklin, supra, 7 Cal.4th at
p. 370.)
      C. There Is No Triable Issue of Fact Under the Locklin
         Reasonableness Test Because that Test Does Not Apply
         Unless There Is a Public Improvement.
      Owners next argue that even if the Government Entities’ management
of Drainage Area 46 did not incorporate the Creek into the public drainage
system, there is still a triable issue of fact as to whether their management of
Drainage Area 46 was unreasonable to support liability under the
“reasonableness” test set forth in Locklin, supra, 7 Cal.4th 327. Owners
concede that the surface water entering the Creek does not drain from any
publicly owned land but argues it does “emanate from improvements
constructed on private parcels under the direct supervision of Respondents.”
      In Locklin, our Supreme Court explained that “[b]ecause a public
agency, like any riparian property owner, engages in a privileged activity
when it drains surface water into a natural watercourse or makes alterations
to the watercourse, article I, section 19, of the California Constitution
mandates compensation only if the agency exceeds the privilege by acting
unreasonably with regard to other riparian owners.” (Locklin, supra,
7 Cal.4th at p. 367.) To determine reasonableness, the court set out the

                                       34
following six factors: “(1) The overall public purpose being served by the
improvement project; (2) the degree to which the plaintiff’s loss is offset by
reciprocal benefits; (3) the availability to the public entity of feasible
alternatives with lower risks; (4) the severity of the plaintiff’s damage in
relation to risk-bearing capabilities; (5) the extent to which damage of the
kind the plaintiff sustained is generally considered as a normal risk of land
ownership; and (6) the degree to which similar damage is distributed at large
over other beneficiaries of the project or is peculiar only to the plaintiff.” (Id.
at pp. 368-369.)
      “However, in determining whether [a public entity] acted unreasonably
in this context, ‘the critical inquiry’ is not whether the public entity acted
reasonably with respect to someone else’s property, but whether ‘the [public
entity] acted reasonably in its maintenance and control over those portions of
the drainage system it does own.’ ” (Ruiz, supra, 47 Cal.App.5th at pp. 526-
527, italics added.) Similarly, as Division Three of this court has held,
“Where a public improvement is unreasonably a substantial cause of the
plaintiff’s damage, a public agency may be liable for its role in diverting
surface water in order to protect urban areas from flooding.” (Skoumbas v.
City of Orinda (2008) 165 Cal.App.4th 783, 796, italics added.) Thus, only
where the public entity owns the property that has caused the harm or by
conduct converts that formerly private property into a public work is the
reasonableness of the public entity’s and the private owner’s conduct
assessed. Because we have held as a matter of law that neither the drainage
improvements nor the Creek was or became a public work, the
“reasonableness” test set forth in Locklin is not implicated. There is
therefore no triable issue of fact raised by this argument.

                                        35
                                       V.
    The Exclusion of Flett’s Custom and Practice Opinion About
 Homeowners’ Associations Was Harmless Because It Did Not Raise a
         Triable Issue Whether an Agreement Was Formed.
      Owners contend the trial court abused its discretion in sustaining the
objection to a paragraph in their expert Flett’s declaration, without
explanation. As we have recognized elsewhere, there is a debate as to
whether the abuse of discretion standard of review that generally applies to
evidentiary rulings should be applied in the context of summary judgment,
where review is generally de novo. (Turley v. Familian Corp. (2017)
18 Cal.App.5th 969, 978.) Owners do not argue we should review the trial
court’s evidentiary ruling de novo here, “ ‘except to the extent the ruling is
based on the court’s conclusion of law.’ ” We need not decide what standard
of review applies to evidentiary rulings made in the summary judgment
context because any error in excluding the opinion in Flett’s declaration was
harmless.
      The trial court excluded Flett’s opinion that if the County had intended
for the drainage improvements in MS 102-72 to be private, it would have
included in the conditions for approval of the subdivision map a requirement
that the property owner assume responsibility for maintaining the drainage
system rather than requiring an irrevocable offer to dedicate the drainage
easements to the County. Flett stated this was the custom and practice of
the County and its failure to include a requirement that the owner form a
homeowners’ association to take responsibility for the drainage
improvements shows the County intended to take responsibility for them.
Owners reprise this argument on appeal, arguing, “the absence of a County
requirement that [the subdivision developer] establish a homeowners’

                                       36
association for the MS 102-72 subdivision to provide for the maintenance of
the drainage system is evidence that the County agreed to maintain it.”
       The Flett opinion, even if admitted, would fail to raise a triable issue
because it exceeds the permissible use of custom and practice evidence.
Generally, offers of dedication are governed by contract principles. (Mikels v.
Rager, supra, 232 Cal.App.3d at pp. 353-354 & fn. 3.) Such offers must be
accepted before they create binding obligations, and a “qualified acceptance of
the offer of dedication [does] not result in a completed dedication of a public
easement.” (Id. at p. 353; Biagini v. Beckham, supra, 163 Cal.App.4th at
p. 1009; Copeland v. City of Oakland (1993) 19 Cal.App.4th 717, 722
[conditional nature of public entity’s acceptance prevents creation of public
liability for street].)
       Under general contract interpretation principles, “[i]t is a well-
established rule that evidence of usage and custom may be introduced as an
instrument of interpretation, but may not be used to create a contract.”
(Magna Development Co. v. Reed (1964) 228 Cal.App.2d 230, 240, italics
added; Weddington Productions, Inc. v. Flick (1998) 60 Cal.App.4th 793, 817.)
Equally well-established is the rule that terms of a contract may be implied
from custom and usage evidence only “ ‘in the absence of agreement to the
contrary.’ ” (Binder v. Aetna Life Ins. Co. (1999) 75 Cal.App.4th 832, 851,
italics added; Miller v. Germain Seed & Plant Co. (1924) 193 Cal. 62, 77; see
Civ. Code, § 1655; 1 Witkin, Summary of Cal. Law (11th ed. 2017) Contracts,
§ 778, pp. 836-837.)
       Applying these principles, custom and usage evidence cannot be used to
establish an acceptance of the offers to dedicate easements or the formation
of any other agreement to maintain the improvements on the dedicated
property. For that reason alone, Flett’s opinion about the “intent” of the

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County, which he infers from the absence of a homeowners’ association
requirement, does not create a triable issue as to whether the County
accepted the offers and thereby undertook to maintain the drainage
improvements.
      There is another reason the Flett opinion does not raise a triable issue
regarding the MS 102-72 subdivision, which is that the term he would imply
conflicts with the express terms of the parties’ agreement. As we have
discussed, in the offer to dedicate, the subdivision developer provided, “It is
understood and agreed that CONTRA COSTA COUNTY and its successor or
assign shall incur no liability with respect to such offer of dedication, and
shall not assume any responsibility for the offered parcel of land or any
improvements thereon or therein, until such offer has been accepted by
appropriate action of the Board of Supervisors, or of the local governing body
of its successor or assign.” (Italics added.) The parties thus agreed that the
County would not become responsible for the improvements unless its Board
of Supervisors took appropriate action to accept the offer of dedication. A
term requiring the County to bear that responsibility without any acceptance
by the Board is contrary to the parties’ express agreement and therefore
cannot be implied based on custom and practice evidence.
      In short, Flett’s opinion about custom and usage fails to raise a triable
issue because it cannot be used for the purposes for which it was offered:
either to imply an acceptance by the County of the offers of dedication and
associated responsibility for the drainage improvements or to imply a term
imposing such responsibility by means other than those specified in the
actual agreement. For these reasons, any error in excluding that opinion is
harmless.

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                                      VI.
          Plaintiffs Concede Their Tort Claims Fail If the Inverse
                       Condemnation Claim Is Not Viable.
      Lastly, Owners concede their related tort causes of action for nuisance,
trespass, and dangerous condition on public property are all conditioned on
the viability of their inverse condemnation claim. For example, Owners
argue that they have a claim for nuisance if it is proven that either the
drainage improvements or the Creek is part of the public drainage system.
Because we conclude they are not, Owners’ tort claims also fail.
                               DISPOSITION
      The judgment is affirmed. Defendants shall recover their costs on
appeal.

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                                        STEWART, P.J.

We concur.

RICHMAN, J.

MILLER, J.

Shenson v. County of Contra Costa (A164045)

                                   40
Trial Court:Contra Costa County Superior Court

Trial Judge:     Hon. Jill C. Fannin

Counsel:

Seiler Epstein, MacKenzie & Albritton, Mark L. Mosley, for Plaintiffs and
Appellants.

Bold, Polisner, Maddow, Nelson & Judson, Timothy J. Ryan, for Defendant
and Respondent.

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